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Multiple Choice Questions

1) A 30-year-old man has been fasting for religious reason for several days.  His brain has reduced its need for glucose by using which of the following substances as an alternate source of energy?

A. Fatty acids

B. Beta hydroxy butyrate

C. Glycerol

D. Beta carotene

E. Alanine

2) A 7-year-old girl is brought to the emergency department by her parents with complaints of severe polyuria and polydipsia. Laboratory examination reveals ketones in her urine. Which of the followings is the most likely source of ketones?

A. Fatty acid breakdown

B. Protein break down

C. Glycogenolysis

D. Gluconeogenesis

E. Side chain of cholesterol

3) A breast-fed infant began to vomit frequently and lose weight. Several days later she developed jaundice, hepatomegaly and bilateral cataract. What is the possible cause for these symptoms? 

A. Galactosemia

B. Von-Gierke’s disease

C. Juvenile diabetes Mellitus

D. Hereditary fructose intolerance

E.  Gaucher disease

4) The major metabolic product produced under normal circumstances by erythrocytes and by muscle cells during intense exercise is recycled through liver in the Cori cycle. The metabolite is-

A. Oxaloacetate

B. Alanine

C. Glycerol

D. Lactate

E. NADH

5) A 3-month-old infant presents with hepatosplenomegaly and failure to thrive. A liver biopsy reveals glycogen with an abnormal, amylopectin like structure with long outer chains and missing branches.  Which of the following enzymes would most likely be deficient?

A. Alpha Amylase

B. Branching enzyme

C. Debranching enzyme

D. Glycogen phosphorylase       

E. Glucose-6-phosphatase          

6) Prior to a race, many marathon runners will try to increase their glycogen concentrations by loading up with foods with high starch content, such as pasta. Alpha amylase secreted by the pancreas will digest the starch into which of the following major products?

A. Amylose, amylopectin, and maltose

B. Glucose, galactose, and fructose

C. Glucose, sucrose, and maltotriose

D. Limit dextrins, maltose, and maltotriose

E. Maltose, glucose and fructose

7) Which of the following substrates cannot contribute to net Gluconeogenesis in mammalian liver?

A. Alanine

B. Glutamate

C. Palmitate

D. Pyruvate

E. Odd chain fatty acids

8) Which of the following complications is less likely to occur in type II diabetics, as opposed to type I diabetics?

A. Retinopathy

B. Weight gain

C. Cardiovascular disease

D. Hypoglycemic coma

E. Non ketotic hyperosmolar coma

9) Familial fructokinase deficiency causes no symptoms because

A. Hexokinase can phosphorylate fructose

B. Liver Aldolase can metabolize it

C. Excess fructose does not escape in to urine

D. Excess fructose is excreted through feces

E. Excess fructose is converted to glucose

10) Which of the followings generates free glucose during the enzymatic breakdown of glycogen in skeletal muscles?

A. Phosphorylase

B. α-1-6-amyloglucosidase

C. Debranching enzyme

D. Glucose-6-phosphatase

E. Alpha amylase

1)   The answer is –B- Beta hydroxy Butyrate, a ketone body. Ketone bodies serve as alternative fuel for brain during prolonged fasting or starvation. Fatty acids due to long hydrophobic chain cannot cross blood brain barrier. Glycerol is a substrate of gluconeogenesis. In fact during prolonged fasting this is the only substrate left to provide glucose through pathway of gluconeogenesis. It can also be oxidized through glycolysis upon phosphorylation. Beta carotene is a provitamin; it is not a source of energy. Alanine is a transporter of amino group of amino acids from the muscle (glucose-alanine cycle), but it cannot be used as an alternative source of energy.

 2)   The answer is –A. Fatty acid break down provides Acetyl co A that serves as a precursor for ketone bodies. In Diabetes Mellitus glucose utilization is impaired due to absolute or relative insulin deficiency. Fatty acid breakdown occurs to provide energy and the resultant excessive Acetyl co A enters the pathway of ketogenesis. Protein breakdown provides amino acids, 6 amino acids are ketogenic, while 14 are glucogenic. Hence protein breakdown contributes only a little towards formation of Acetyl co A. The major contribution is through fatty acid breakdown. Glycogenolysis and Gluconeogenesis produce glucose only. Side chain of cholesterol provides propionyl co A which is a glucogenic component; it is converted to succinyl co A to gain entry in to TCA cycle.

 3)   The answer is –A. Galactosemia. The clinical manifestations are typical of classical Galactosemia. Bilateral cataract rules out the possibility of Von Gierke’s disease and hereditary fructose intolerance, although other symptoms are there in both these diseases. In juvenile diabetes mellitus, jaundice and hepatomegaly are not observed. In Gaucher disease, hepatomegaly is observed but cataract is never there.

 4)   The answer is-D- Lactate, the end product of glycolysis in erythrocytes and during intense exercise in skeletal muscle, is mobilized through Cori cycle to liver to provide glucose by the process of gluconeogenesis. (Erythrocytes lack mitochondria so the end product of glycolysis is always lactate.  The mode of glycolysis during intense exercise is anaerobic; hence lactate is formed as a result of glycolysis.

Alanine is transported to liver through Glucose Alanine cycle. Glycerol is also similarly transported but not from the erythrocytes or skeletal muscles, rather from the adipose tissues. Glycerol is a waste product in adipose tissues since without phosphorylation it cannot be utilized and the phosphorylating enzyme glycerol kinase is absent in adipose tissues.

 NADH produced at the step of glyceraldehyde dehydrogenase step is regenerated in the oxidized form NAD+ by reduction of pyruvate to lactate. These two reactions are coupled to have a continuous supply of NAD+.

 5)   The answer is-B- Branching enzyme. During the process of glycogen synthesis, branching enzyme creates branch points and further elongation is carried out by Glycogen synthase. In its deficiency stored glycogen is abnormal in chemistry, in the form of long polysaccharide chains with few branch points, resembling the structure of Amylopectin, thus this defect is also called Amylopectinosis. Alpha Amylase is an enzyme for digestion of starch and glycogen. Debranching enzyme deficiency results in the accumulation of abnormal glycogen, There is inability to remove the branch points, the resultant structure resembles Limit dextrin, and thus it is also called Limit dextrinosis. Glucose-6-phosphatase deficiency is observed in Von-Gierke’s diseases, a type 1 glycogen storage disease, the stored glycogen is always normal in chemistry.

 6)   The answer is-D.  The hydrolysis of starch is catalyzed by salivary and pancreatic amylases, which catalyze random hydrolysis of alpha (1- 4) glycoside bonds, yielding dextrins, and further hydrolysis yields a mixture of glucose, maltose, isomaltose (from the branch points in amylopectin) and maltotriose. Sucrose, galactose and fructose are not components of starch.

 7)   The answer is- C. Palmitate, a fatty acid with 16 carbon atoms, is not a substrate of gluconeogenesis. Even chain fatty acids, predominantly present in our body, yield Acetyl co A upon oxidation, which can not contribute towards gluconeogenesis.  The Pyruvate to Acetyl co A conversion is irreversible and moreover both of the carbon atoms of Acetyl co A are lost in the TCA cycle in the form of CO2.Oddchain fatty acid do act as substrates of gluconeogenesis, since propionyl co A the product of their oxidation can enter TCA cycle through formation of Succinyl co A, hence can contribute towards Glucose production. Alanine, pyruvate and glutamine are glucogenic.

 8)   The answer is-D- Hypoglycemic coma occurs as a result of insulin over dosage in Type 1diabetes Mellitus.  It is not observed in Type 2 diabetes. Weight gain can occur in both types, it is the result of treatment with insulin or certain hypoglycemic drugs. Non ketotic hyperosmolar coma is a frequent complication of coma especially in the elderly group.

 9)   The answer is-A Hexokinase is a non specific enzyme, it can phosphorylate fructose as well as other sugars but it has high km (low affinity) for fructose.  Glucose is the true substrate for this enzyme.Fructose-6-phosphatethe end product of Hexokinase reaction can enter glycolytic pathway to be utilized further, so it does not accumulate to produce the toxic effects. Liver Aldolase (Aldolase B) cleaves Fructose-1-P only, the product of fructokinase catalyzed reaction.  Aldolase A, present in all the cells of the body cleaves Fructose 1, 6 bisphosphate, the product of PFK-1 catalyzed reaction of glycolysis. Fructose to glucose conversion takes place only in the phosphorylated form.

 10) The answer is-B- Free glucose is released by the action of α-1-6-amyloglucosidase enzyme, a component of debranching enzyme. Debranching enzyme has two components. α-[1 4] to α-[1 4] Glucan transferase and α-1-6-amyloglucosidase.Glucan transferase shifts the trisaccharide on a branch bound by α-[1- 4] linkage to the straight chain and joins by α-[1 4] linkage. The exposed branch point is hydrolyzed by α-1-6-amyloglucosidase enzyme. Both components are present on the same polypeptide chain. Glucose-6- phosphatase does produce free glucose but it is absent in skeletal muscles. Alpha amylase is a digestive enzyme; it has no role in glycogen degradation in the muscle.

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1) An infant presents with an enlarged heart, muscle weakness, and hypoventilation. She is diagnosed with glycogen storage disease type II, a disease-causing, abnormal glycogen storage in the heart, skeletal muscle and respiratory  muscles. Glycogen synthase is the regulatory enzyme for glycogen synthesis. It adds glucose residues to the nonreducing ends of a glycogen primer from:

a) Glucose-1-P

b) Glucose-6-P

c) UDP- Glucose

d) UTP

e) ATP.

2) A 30- year-old male presents with severe muscle cramps. He is found to have muscle glycogen phosphorylase deficiency(Mc Ardle’s disease, Glycogen storage type 5).Glycogen phosphorylase degrades glycogen to produce-

a) Glucose

b) Glucose-1-P

c) Glucose-6-P

d) UDP Glucose

e) Glycogen Primer

3) A 15-year-old  type 1 diabetic faints after injecting himself  with insulin. He is administered Glucagon  and rapidly recovers consciousness. Glucagon induces activity of:

a) Glycogen synthase

b) Glycogen phosphorylase

c) Glucokinase

d) Hexokinase

e) UDP Glucose pyrophosphorylase.

4) A 30-year-old presents with intractable vomiting and inability to eat or drink for the past 3 days. His blood glucose level is normal. Which of the following is most important for maintenance of blood glucose ?

a) Liver

b) Heart

c) Skeletal muscle

d) Lysosome

e) Spleen.

5) Shortly after birth, an infant presents with tremors, irritability and seizures. His blood glucose is profoundly low, and he is fed through a nasogastric tube. he is diagnosed with glycogen storage disease type I, a disease that causes excessive build up of liver glycogen, resulting in abnormally low blood glucose level. In glycogen, the linkage at branch points is:

a) α -1,4

b) α-2,3

c) α-1,6

d) β-1,4

e) β-2,3.

6) A 15-year-old male presents with increased thirst, hunger, urination, and weight loss. His fasting blood glucose level is 400 mg/dl and is diagnosed with type 1 diabetes mellitus. What is the reason for this patient’s inability to maintain a normal blood glucose level ?

a) Decreased uptake  of glucose by peripheral cells

b) Abnormal response to glucagon

c) Decreased glucagon to insulin ratio

d) Decreased glucose output by the liver

e) Increased ketone body production.

7) Which enzyme is not present in muscle ?

a) Phosphorylase b

b) Hexokinase

c) Glucose-6-phosphatase

d) Glycogen synthase

e) Lactate dehydrogenase

8) Glycogenolysis is best described by which of the following statements ?

a) It involves enzymes cleaving β, 1-4 glycosidic linkage

b) Requires activation of glycogen synthase

c) Requires a dual action enzyme α-1,4 glycosidase and transferase

d) Uses ATP to produce glucose-1-P

e) Requires inactivation of phosphorylase kinase.

9) Glycogenesis from Glucose-1-P requires which of the following ?

a) Phosphoglucomutase

b) Uridine triphosphate (UTP)

c) α-1,6 glucosidase

d) Glycogen primer

e) Uridine diphosphate

10) In glycogen, glucose residues form a straight chain via which of the following-

a) α -1,4 linkages

b) α -1,6 linkages

c) α -1,4 linkages with glycogenin at the non reducing end

d) α -1,6 linkages with UDP glucose at any end

e) straight chain occurs at 3 residues apart

11) In the liver Epinephrine induced glycogenolysis :

a) Requires UDP glucose pyrophosphorylase

b) Requires Phosphoglucomutase

c)Requires inactivation of phosphorylase a

d) Inhibited by c AMP

e) acts upon both liver and muscle cells, similar to glucagon.

12) Glycogen catabolism is best described by which of the following statements-

a) In the brain, it yields glucose for skeletal muscle consumption

b) It requires a debranching enzyme in the erythrocytes

c) It is not a major pathway in the brain

d) It uses phosphorylase for glucose residue cleavage from the reducing end of glycogen in liver

e) It is stimulated by Insulin in liver.

13) During the breakdown of glycogen, free glucose is formed from which of the following ?

a) Glucose residues in α-1,4 glycosidic linkages

b) The reducing end

c) The non reducing end

d) Glucose residues in  α-1,6 glycosidic linkages

e) Hydrolysis of glucose-1-P

14) Which of the following statements explains the synthesis of glycogen directly from D- Glucose ?

a) It does not use glucose-1-P

b) It requires a debranching enzyme

c) It occurs in erythrocytes.

d) It requires UDP-Glucose

e) It requires a glucosyl transferase

15)The degradation of glycogen normally produces which of the following ?

a) More glucose than Glucose-1-P

b) More Glucose-1-P than Glucose

c) Equal amount of Glucose and Glucose-1-P

d) Neither Glucose nor Glucose-1-P

e) Only Glucose-I-P

16) Which of the following statements about liver phosphorylase kinase is most accurate ?

a) It is present in the inactivated form when epinephrine is released

b) It phosphorylates phosphorylase to make it inactive

c) It is stimulated by c AMP mediated phosphorylation cascade

d) It is not affected by ATP

e) It is phosphorylated in response to Insulin.

17) A newborn is found to have fasting hypoglycemia. The nursery staff begins overnight feeds by nasogastric tube because they find that the child consistently has low blood glucose. A liver biopsy and molecular studies demonstrate an absence of Glycogen synthetase. The normal function of this enzyme is to do which of the followings ?

a) Remove glucose residues one at a time from glycogen in liver

b) Remove glucose residues one at a time from glycogen in muscles

c) Transfer UDP glucose to the non reducing end of glycogen primer

d) Hydrolyze α-1,6 bonds of glycogen

e) Function as a glucosyl 4:6 transferase.

18) A 3-year-old child presents to the pediatrician for failure to thrive. A workup including an ultrasound of his liver shows cirrhosis. A biopsy of liver demonstrates a deficiency of an enzyme involved in glycogen synthesis. Which of the following is the most likely glycogen storage disease ?

a) Type I -Von Gierke’s disease

b)Type II – Pompe’s disease

c) Type III- Cori’s disease

d) Type IV- Andersen’s disease

e) Type V- McArdle disease

19) A new-born is experiencing failure to thrive. On physical examination, organomegaly is appreciated due to accumulation of glycogen in the lysosomes of several organs, including the heart, muscle and liver. A diagnosis of Pompe’s disease is made. Which of the following biochemical deficits are seen in this disorder ?

a) Glycogenin deficiency

b) An α-1,6 glycosidase deficiency

c) A glucose-6-phosphatase deficiency

d) A glycogen phosphorylase deficiency

e) A lysosomal glucosidase deficiency

20) A second year medical student decides to do research in a nutrition laboratory that is studying the effect of caffeine on cellular metabolism. Caffeine inhibits cAMP phosphodiesterase. If  caffeine is added to cells, which of the following enzymes is  phosphorylated and inactivated in liver ?

a) Phosphorylase kinase

b) Calmodulin

c) Phosphorylase

d) Protein kinase A

e) Glycogen synthase

21) A 28-year-old professional cyclist has been training for an opportunity to go for a long race. His coach strongly suggests the intake of carbohydrates after the work out to ensure a  muscle glycogen storage that can endure the 28-day race. The activity of muscle glycogen synthase in resting muscles is increased by the action of which of the following?

a)Epinephrine

b) Glucagon

c) Insulin

d) Phosphorylation

e) Fasting and starvation.

22) An infant was brought in to the emergency room after her parents witnessed her having seizures. The child’s blood glucose was 28 mmol/L. After a thorough workup, a GSD  was suspected, and a muscle biopsy was significant for the accumulation of dextrin, a form of glycogen with branching limited to only a few glucose molecules. Which of the following GSD is most likely the cause of hypoglycemia and subsequent seizures ?

a) Type I -Von Gierke’s disease

b)Type II – Pompe’s disease

c) Type III- Cori’s disease

d) Type IV- Andersen’s disease

e) Type V- McArdle disease

 

 Key to Answers

1) c, 2)-b, 3)-b, 4)-a, 5)-c, 6)-a, 7)-c, 8)-c, 9)-d, 10)-a, 11)-b, 12)-c, 13)-d, 14)-d, 15)-b, 16)-c, 17)-c,18)-d,   

19)-e, 20)-e, 21)-c, 22)-c.

 

 

 

 

 

 

 

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1) Glucose breakdown in certain mammalian and bacterial cells can occur by mechanisms other than classic glycolysis. In most of these, glucose 6-phosphate is oxidized to 6- phosphogluconate, which is then further metabolized by:

a) an aldolase-type split to form glyceric acid and glyceraldehyde 3-phosphate.

b) an aldolase-type split to form glycolic acid and erythrose 4-phosphate.

c) conversion to 1,6-bisphosphogluconate.

d) decarboxylation to produce keto- and aldopentoses

e) oxidation to a six-carbon dicarboxylic acid.

2) Which of the following enzymes acts in the pentose phosphate pathway?

a) 6-phosphogluconate dehydrogenase

b) Aldolase

c) Glycogen phosphorylase

d) Phosphofructokinase-1

e) Pyruvate kinase

3) The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

a) 2 mol of pentose, 4 mol of NADPH, and 8 mol of CO2.

b) 3 mol of pentose, 4 mol of NADPH, and 3 mol of CO2.

c) 3 mol of pentose, 6 mol of NADPH, and 3 mol of CO2.

d) 4 mol of pentose, 3 mol of NADPH, and 3 mol of CO2.

e) 4 mol of pentose, 6 mol of NADPH, and 6 mol of CO2.

4) In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be expected to end up principally in:

a) Carbon dioxide

b) Glycogen

c) Phosphoglycerate

d) Pyruvate

e) Ribulose 5-phosphate

5) The main function of the pentose phosphate pathway is to:

a) give the cell an alternative pathway should glycolysis fail

b) provide a mechanism for the utilization of the carbon skeletons of excess amino acids

c) supply energy

d) supply NADH

e) supply Pentoses and NADPH

6) Which of the following statements about the pentose phosphate pathway is correct?

a) It generates 38 mol of ATP per mole of glucose consumed.

b) It generates 6 moles of CO2 for each mole of glucose consumed

c) It is a reductive pathway; it consumes NADH.

d) It is present in plants, but not in animals.

e) It provides precursors for the synthesis of nucleotides.

7) The reactions of the pentose phosphate pathway using glucose-6 phosphate as the initial substrate are best described by which of the following statements ?

a) They produce 2 moles of NADPH for each mole of CO2 released.

b) They generate 2 moles of adenosine triphosphate per mole of glucose-6-phosphate metabolized to ribulose-5 phosphate.

c) They occur in the matrix of mitochondria.

d) They are not required for the production of NADPH in the mature red blood cells

e) They are required for the  metabolism of glucose in the muscles.

8) In the pentose phosphate pathway, the major products are which of the followings ?

a) Ribulose and ATP

b) Ribulose and NADPH

c) Ribose and NADH

d) Ribose and NAD+

e) Xylulose and ATP

9) Which of the following statements about the oxidative section of the pentose phosphate pathway is correct?

a) The pentose phosphate pathway generates NADH.

b) The pentose phosphate pathway oxidizes NADPH to NADP+

c) The rate-limiting reaction of the pentose phosphate pathway is catalyzed by glucose-6-phosphatase.

d) The pathway supplies ribose-5-phosphate and NADPH in the quantities the cells requires.

e) The pathway is highly active in the fasting state.

10) Which of the following statements about the nonoxidative section of the pentose phosphate pathway is correct?

a) The nonoxidative reactions of the pentose phosphate pathway are not reversible.

b) Transketolase is an enzyme that transfers three-carbon units in the pentose phosphate pathway

c) Transaldolase is an enzyme that transfers two-carbon units in the pentose phosphate pathway

d) Pentoses can provide glycolytic intermediates in this phase of HMP pathway

e) Pentoses can be metabolized to provide NADPH in this phase of HMP pathway.

11) Which of the following statements about the use of the NADPH generated from the pentose phosphate pathway is not correct?

a) NADPH generated from the pentose phosphate pathway is used for steroid synthesis.

b) NADPH generated from the pentose phosphate pathway is used for the regeneration of glutathione to its reduced state.

c) NADPH generated from the pentose phosphate pathway is used for the synthesis of fatty acids

d) NADPH generated from the pentose phosphate pathway can be oxidized in the electron transport chain to provide 38 ATPs

e) NADPH generated from the pentose phosphate pathway is used for the Macrophageal functions.

12) A 19- year-old, African-American male military recruit is about to be sent to Iraq on his assignment. In preparation for his tour of duty, he is given a prophylactic dose of primaquine to prevent malaria. Several days after he develops fatigue and hemolytic anemia. Which of the following enzymes is likely deficient ?

a) Fructokinase

b) Aldolase B

c) Glucose-6-P dehydrogenase

d) Galactokinase

e) Galactosyl Transferase.

13) A 50 -year-old alcoholic male presents with pain, numbness, tingling and weakness in his feet. He is diagnosed with thiamine deficiency. Thiamine and ATP condense together to form   thiamine pyrophosphate, a cofactor important for the enzymes that catalyze oxidative decarboxylation of (α-keto acids) in the TCA cycle and also at one of the steps in pentose phosphate pathway, which out of the following enzymes requires TPP as a coenzyme ?

a) Glucose-6-P dehydrogenase

b) Transaldolase

c) Transketolase

d) 6-P-Gluconate dehydrogenase

e)  Gluconolactone hydrolase.

14) The key regulatory enzyme of HMP pathway is-

a) Glucose-6-P dehydrogenase

b) Transaldolase

c) Transketolase

d) 6-P-Gluconate dehydrogenase

e)  Gluconolactone hydrolase.

15) Xylulose 5-phosphate can be formed from Ribulose 5-phosphate by the action of-

a) Glucose-6-P dehydrogenase

b) Transaldolase

c) Transketolase

d) Phosphopentose epimerase

e)Phosphopentose isomerase.

16)-The pentose phosphate pathway is active in liver, adipose tissue, adrenal cortex, thyroid, erythrocytes, testis, and lactating mammary gland. Why is the pathway less active in skeletal muscle?

a) Muscle tissue contains very small amount of dehydrogenases

b) Muscle tissues do not require NADPH

c) Pentoses the major product of this pathway are not required by muscle tissue

d) Muscle tissue contains very small amount of enzymes of non oxidative phase

e) All of the above.

17) In rapidly dividing cancer cells the need for large amount of ribose is fulfilled by-

a) Highly active Glucose-6-P dehydrogenase

b) Highly active Transaldolase

c) Highly active Transketolase

d) Highly active 6-P-Gluconate dehydrogenase

e) Reversal of non oxidative phase using glycolytic intermediates.

 

 Answers-        1)-d                2)-a                  3)-c                  4)-a                  5)-e                 

                        6)-b                 7)-a                  8)-b                 9)-d                 10)-d

                        11)-d               12)-c                13)-c                14)-a                15)-d

                        16)-a                17)-e

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1)  A 4-month-old boy is being evaluated for seizures, psychomotor retardation, and hypotonia. Work up reveals elevated serum levels of lactate, alanine, pyruvate and keto acids. Based on the clinical presentation,pyruvate carboxylase activity is measured using fibroblasts from a skin biopsy and is found to be markedly decreased. This enzyme is normally used to directly synthesize which of the following molecules ?

a) Pyruvate

b) Oxaloacetate

c) Malate

d) Acetyl co A

e) α- Keto glutarate

2) A 34-year-old woman presents with central obesity, relatively thin extremities and purple stria on her abdomen. Further work up reveals an excessive serum cortisol level and a blood sugar level of 258 mg/dl. Which of the following is the most likely cause of her hyperglycemia ?

a) Excessive consumption of processed carbohydrates

b) A pancreatic adenoma secreting  ACTH and glucagon

c) Cortisol induced inhibition of insulin

d) Glucorticoids cause induction of Phosphoenolpyruvate carboxy kinase gene

e) Increased gluconeogenesis due to increased provision of substrates through fatty acid oxidation.

3) A 56-year-old, obese man complains of polydipsia, polyuria and fatigue. A glucose tolerance test confirms the diagnosis of diabetes. He is placed on Metformin, which works by which of the following mechanisms ?

a) Inhibiting hepatic gluconeogenesis

b) Increasing glucagon level

c) Increasing cellular responsiveness to circulating insulin

d) Stimulating the release or preformed insulin

e) Replacing the need for endogenous insulin

4) An enzyme used in both glycolysis and gluconeogenesis is:

a) 3-phosphoglycerate kinase.

b) Glucose 6-phosphatase

c) Hexokinase

d) Phosphofructokinase-1

e) Pyruvate kinase

5) Which one of the following statements about gluconeogenesis is false?

a) For starting materials, it can use carbon skeletons derived from certain amino acids.

b) It consists entirely of the reactions of glycolysis, operating in the reverse direction.

c) It employs the enzyme glucose 6-phosphatase.

d) It is one of the ways that mammals maintain normal blood glucose levels between meals.

e) It requires metabolic energy (ATP or GTP).

6) All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are

also involved in the reversal of this flow (gluconeogenesis) except:

a) 3-phosphoglycerate kinase.

b) Aldolase

c) Enolase

d) Phosphofructokinase-1

e) Phosphohexoseisomerase

7) In humans, gluconeogenesis:

a) can result in the conversion of protein into blood glucose.

b) helps to reduce blood glucose after a carbohydrate-rich meal.

c) is activated by the hormone insulin

d) is essential in the conversion of fatty acids to glucose.

e) requires the enzyme hexokinase.

8) Which of the following substrates cannot contribute to net gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Palmitate

d) Pyruvate

e) α-Keto glutarate.

9) A 6-year-old boy begins playing soccer in a community league. After his first game of the year, he is brought to see his pediatrician because of his severe muscle cramps and blood in urine. He is subsequently found to be having deficiency of lactate dehydrogenase. This enzyme is important in which of the following conversions ?

a) Pyruvate to Acetyl co A

b) Pyruvate to Oxaloacetate

c) Pyruvate to Alanine

d) Pyruvate to Phosphoenol pyruvate

e) Pyruvate to lactate

10) A new-born infant is found to be having persistent hypoglycemia, despite decreased feeding intervals. The child is also irritable with a moderate degree of hepatomegaly. He is found to have a normal level of muscle fructose 1,6 bisphosphatase but decreased level of liver isoform. Which of the following statement is true of fructose 1,6 bisphosphatase?

a) It is induced by Adenosine mono phosphate (AMP)

b) It is induced by Insulin

c) It is inhibited by Fructose 2,6 bisphosphate

d) It is induced in the fed state

e) It is inhibited during fasting.

11) A 14-year-old  high school girl who is extremely conscious about her appearance has gone a full day fasting to fit in to a dress she intentionally brought a size smaller than her actual size for a dance party. Which of the following organs/tissues contributes to the glucose  that is being synthesized through gluconeogenesis ?

a) Spleen

b) Red blood cells

c) Skeletal muscle

d) Liver

e) Brain

12) An 8 -year-old boy presents with frequent episodes of weakness, accompanied by sweating and feelings of dizziness. Physical examination is remarkable for palpably enlarged liver and kidneys. Blood biochemistry reveals lactic acidemia. The patient is diagnosed with deficiency  of glucose-6-phosphatase, which is normally only expressed in-

a) Liver and muscle

b) Liver and brain

c) Erythrocytes

d) Liver and adipose tissues

e) Liver and kidney.

13)  A 32-year-old body builder has decided to go on a diet consisting of egg whites to ensure only proteins for muscle growth. After a few weeks he experiences  decreased energy and is found to be hypoglycemic. A nutritionist tells the patient that he most likely has the deficiency of vitamin Biotin. Which of the following enzymes is unable to catalyze its step in synthesizing glucose from pyruvate?

a) Pyruvate carboxylase

b) Phospho enol pyruvate carboxy kinase

c) Glucose-6-phosphatase

d) Fr 1,6 bisphosphatase

e) Phosphoglycerate kinase.

14) In an individual at rest, who has fasted for 12 hours, which of the following occurs ?

a) Gluconeogenesis is the major process by which blood glucose is maintained

b) Liver glycogen stores are depleted

c) Glycogen synthase is activated in liver

d) Adenylate cyclase is inactivated in liver

e) Phosphorylase, pyruvate kinase and glycogen synthase are phosphorylated in liver.

15) Which of the following is a common intermediate in the conversion of glycerol and lactate to glucose ?

a) Pyruvate

b) Oxaloacetate

c) Malate

d) Glucose-6-phosphate

e) Phosphoenolpyruvate.

16) In the conversion of pyruvate to glucose during gluconeogenesis,

a) Biotin is required

b) CO2 added in one reaction, appears in the final product

c) Energy is used up in the form of GTP

d) All the reactions take place in the cytosol

e) PDH is the allosteric enzyme used.

17) Which of the following glycolytic enzymes is used in gluconeogenesis ?

a) Glucokinase

b) Phosphofructokinase-1

c) Aldolase B

d) Phosphoglycerate kinase

e) Pyruvate kinase.

18) The conversion of pyruvate to fructose 1,6 bisphosphate by the gluconeogenic pathway involves which of the followings ?

a) Requires lactate dehydrogenase

b) Requires hexokinase

c) Produces 2 ATP and 2GTP

d) Requires 4 ATP and 2 GTP

e) Acetyl co A is not required to activate this pathway.

19) A high ratio of insulin to glucagon can:

a) Promote gluconeogenesis

b) Promote glycogenolysis

c) Found in Type 1 Diabetes Mellitus

d) Occurs during fasting state

e) Promotes synthesis of  Glycogen

20) Which of the following is a precursor for gluconeogenesis ?

a) Glycogen

b) Glycerol

c) Glucagon

d) Galactose

e) Glucose-1- P.

 

Answers-  1)-b ,  2)-d,  3)-a,  4)-a,  5)-b,  6)-d,  7)-a,  8)-c,  9)-e,  10)-c,  11)-d,  12)-e,  13)-a,  14)-e,  15)-d,  16)-a ,17)-d,  18)-d,  

19)-e,  20)-b.

 

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1) A 24-year-old woman presents with diarrhea, dysphagia, jaundice and white transverse lines on the fingernails (Mee’s lines). The patient is diagnosed with Arsenic poisoning,that inhibits which of the following enzymes of TCA cycle ?

a) Citrate synthase

b) Isocitrate dehydrogenase

c) α-Keto glutarate dehydrogenase complex

d) Succinate dehydrogenase

e) Malate dehydrogenase

2)  A biochemistry graduate student  isolated all enzymes of TCA cycle to produce NADH, oxidation of which of the following substrates in the citric acid cycle is not coupled to the production of NADH ?

a) Succinate

b) Malate

c) α-Keto glutarate

d) Isocitrate

e) Pyruvate.

3) A 3-Year-old boy presents to the pediatric clinic with the symptoms of hypotonia, lactic acidosis, and seizures. After an extensive workup , he is diagnosed with pyruvate dehydrogenase complex deficiency. Which of the following cofactors is not required by this enzyme to convert pyruvate to Acetyl co A ?

a) Thiamine

b) Lipoic acid

c) Pantothenic acid

d) Niacin

e) Ascorbic acid.

4) Which of the following vitamins is required for the synthesis of a cofactor required for the conversion of Succinate to Fumarate?

a) Thiamine

b) Lipoic acid

c) Pantothenic acid

d) Niacin

e) Riboflavin.

5) Pyruvate dehydrogenase complex deficiency is an autosomal recessive disorder and leads to anion gap metabolic acidosis. Which of the following accumulates  to cause metabolic acidosis ?

a) Beta hydroxy butyric acid

b) Acetoacetic acid

c) Fumaric acid

d) Lactic acid

e) Hydrochloric acid.

6) A 3 year-old child presents with a history of recurrent rash upon sun exposure and passage of purple colored urine. The child is diagnosed  with  Congenital Erythropoietic  Porphyria, a disorder of pathway of haem biosynthesis. Which of the following intermediates of TCA cycle is used as a precursor for  haem biosynthesis ?

a) Succinyl co A

b) Acetyl co A

c) Succinate

d) Malate

e) Pyruvate

7) A 16 -year-old male comes to the clinic for a routine sports physical examination. His physical examination is unremarkable except for the skin findings of multiple pale masses which appear to be xanthomas. Xanthomas are generally associated with the underlying hypercholesterolemia. Which of the following is utilized as a precursor for cholesterol biosynthesis ?

a) Succinyl co A

b) Acetyl co A

c) Succinate

d) Malate

e) Pyruvate.

8) A 2-year-old child was brought to pediatric emergency with convulsions. The child was diagnosed with ammonia intoxication due to some urea cycle disorder. Reduced formation of GABA  is considered to be the most important cause of convulsion due to depletion of glutamate from where it is produced by decarboxylation. Which of the following intermediates of TCA cycle is involved in the formation of Glutamate ?

a) Succinate

b) Malate

c) α-Keto glutarate

d) Isocitrate

e) Pyruvate.

9) In TCA cycle , GTP is produced at one step by substrate level phosphorylation and that is subsequently utilized for Gluconeogenesis. Which of the following enzymes is involved in this process of formation of GTP from GDP ?

a) Succinate Thiokinase

b) Succinate dehydrogenase

c) Citrate synthase

d) Isocitrate dehydrogenase

e) Malate dehydrogenase

10) A  5-year-old child was rushed to pediatric emergency as he accidently consumed Fluoroacetate, a known inhibitor of TCA cycle. Which of the following enzymes is inhibited by  fluoroacetate?

a) Citrate synthase

b) Aconitase

c)  Succinate dehydrogenase

d) Isocitrate dehydrogenase

e) Malate dehydrogenase.

11) Malonate is an inhibitor of-

a) Citrate synthase

b) Aconitase

c)  Succinate dehydrogenase

d) Isocitrate dehydrogenase

e) Malate dehydrogenase.

12) A 56-year- old chronic alcoholic has been  brought in a semiconscious state to the medical emergency. Blood biochemistry reveals hypoglycemia  with blood glucose level of 45 mg/dl. Which of the following intermediates of TCA cycle can be directly converted to phosphoenolpyruvate to trigger the pathway of gluconeogenesis ?

a) Succinate

b) Malate

c) α-Keto glutarate

d) Oxaloacetate

e) Pyruvate.

13) A 78-year-old male is brought to emergency with Acute myocardial infarction. Blood biochemistry reveals lactic acidosis. How much energy yield (ATP) per mol of glucose is expected in such a condition?

a) 32

b)2

c) 34

d) 36

d) 38

14) Which of the following allosteric modulators  is not effective in influencing the rate of TCA cycle ?

a) NADH

b) FADH2

c) Ca++

d) ADP

e) ATP

15)  How many molecules of CO2 are produced per mole of Acetyl co A in TCA Cycle ?

a) 2

b) 1

c) 3

d) 0

e) 4

16) The cytosolic isoform of which of the following TCA cycle enzymes requires NADP+ as a coenzyme, that can further be utilized in the reduced state for reductive biosynthesis?

a) Citrate synthase

b) Aconitase

c)  Succinate dehydrogenase

d) Isocitrate dehydrogenase

e) Malate dehydrogenase.

17) Which of the following intermediates of TCA cycle is depleted  in Type 1 Diabetes mellitus to suppress TCA cycle and to channel excess Acetyl co A towards pathway of ketogenesis ?

a) Succinate

b) Malate

c) α-Keto glutarate

d) Oxaloacetate

e) Pyruvate.

18)- Which of the following enzymes is Thiamine dependent and essential for glucose oxidation in the brain?

a) Pyruvate dehydrogenase complex                    

b) Acetyl co A carboxylase

c) Transaldolase                                               

d) Succinyl-co A Thiokinase

e) Succinate dehydrogenase     

19)-Anaplerotic reactions are those that result in replenishing intermediates in the TCA cycle. Which of the following enzymes catalyzes an anaplerotic reaction?

a) Malate dehydrogenase

b) Pyruvate carboxylase

c) Pyruvate kinase

d) Citrate synthase

e) Succinyl-co A Thiokinase

20) -Which of the following intermediates of TCA cycle cannot be utilized for gluconeogenesis ?

a) Succinate

b) Malate

c) α-Keto glutarate

d) Oxaloacetate

e) Acetyl co A.

Answers -1) -c,  2) -a , 3) -e , 4)-e , 5)-d , 6)-a , 7)-b , 8) -c , 9) -a , 10 )-b , 11) -c,  12)-d,  13) -b , 14) -b,  15) -a , 16) -d, 17) -d ,

18)-a,  19) -b,  20) -e                   

 

 

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1). A patient has chronic obstructive pulmonary disease, enough oxygen is not reaching her tissues.  All of the followings are  expected except-

a) The electron transport chain would be inhibited

b) Glycolysis would be activated by a low ATP/ADP ratio

c) More than normal amounts of ATP would be synthesized .

d) Concentrations of NADH and pyruvate would be lower than normal

e) More than normal amounts of lactate would be produced

2). A 45- year- old woman is diagnosed with breast cancer. The oncologist orders a positron emission tomography(PET) scan of the head to rule out metastasis. This imaging modality covalently links a radioactive isotope most commonly to Glucose to appreciate highly active areas in the body such as tumor. Which of the following traps the tracer in the cell ?

a) Insulin

b) GLUT-1

c) GLUT-4

d) Glucokinase

e) PFK-1

3) A 45-year-old obese man complains of having to get up frequently to urinate at night-time. He has also noticed that he is constantly thirsty and hungry. The patient is diagnosed with type 2 diabetes mellitus. If this is a problem at the level of glucose transporters , which tissue would be most affected?

a) Liver

b) Red blood cells

c) Muscle and adipose tissue

d) Brain tissue

e) Small intestine.

4) A 24-year woman is getting training for her first marathon. Her coach instructed her to keep a pace that allows her to stay below her anaerobic threshold. Under such conditions pyruvate does not accumulate as it is converted to-

a) Ethanol

b) Lactic acid

c) Acetyl co A

d) Alanine

e) Oxaloacetate.

5) A patient presents with dizziness, fatigue and tremors. A fingerstick test indicates a blood glucose level of 45 mg/dl (hypoglycemia). Glucagon is released under such condition . Which of the following allosteric modifier of PFK-1 would be  most effective in switching off glycolysis ?

a) Low level of citrate

b) Low level of Fr, 2,6 bisphosphate

c) Low level of ATP

d) Low level of NAD+

e) Low level of Glucose-6-P

6) A 30 -year-old woman is enduring her second trimester of pregnancy. The  greater affinity fetal hemoglobin acquires oxygen released from the lesser affinity maternal hemoglobin due to the effect of an allosteric modifier, which is-

a) Fr-2,6 bisphosphate

b) 2,3 bisphosphoglycerate

c) Citrate

d) Acetyl co A

e) Fr-1,6 bisphosphoglycerate

7) A pediatric hematologist sees an 18 month-old patient with jaundice, splenomegaly and hemolytic anemia. Blood smear indicates red blood cells that are more rigid in appearance than normal. A diagnosis of pyruvate kinase deficiency is made. What products would be made in low amounts ?

a) Acetyl co A

b) Glucose

c) Lactate

d) ATP

e) Alanine

8)  In an embryo with a complete deficiency of pyruvate kinase, how many net moles of ATP would be generated in the conversion of one mole of glucose to one mole of pyruvate ?

a) 0

b) 1

c) 2

d) 3

e) 4

9) Which out of the following enzymes cleaves a carbon-carbon bond in the pathway of glycolysis ?

a) Aldolase

b) Glyceraldehyde-3-P dehydrogenase

c) Enolase

d) Phosphoglycerate kinase

e) Phosphoglycerate mutase

10) After a heavy meal, which out of the following allosteric activator would be most effective in increasing the rate of glycolysis ?

a) ATP

b) Citrate

c) Acetyl co A

d) Fr-2,6 bisphosphate

e) 2,3 bisphosphoglycerate.

11) Compared with the resting state a vigorously contracting muscle shows-

a) An increased conversion of pyruvate to lactate

b) Increased oxidation of pyruvate to CO2

c) A decreased concentration of AMP

d) Decreased level of fr-2,6 bisphosphate

e) Decreased ratio of NADH/NAD+

12) A 24 -year-old man presented with symptoms of shortness of breath, weakness and fatigue. His Hemoglobin level was 7G/dl. Red blood cell isolated from the patient showed abnormally low-level of lactate. A deficiency of which of the following enzymes would be the most likely cause for patient’s anemia?

a) Phosphoglucose isomerase

b) Phosphofructokinase

c) Hexokinase

d) Glucokinase

e) Pyruvate kinase.

13) A mixture of sodium fluoride and potassium oxalate is added to sample collected for blood glucose estimation to prevent loss of glucose by anaerobic glycolysis. Fluoride is an inhibitor of glycolysis. Which of the following enzymes is inhibited by fluoride ?

a) Hexokinase

b) Phosphofructokinase

c) Glyceraldehyde-3-P dehydrogenase

d) Lactate dehydrogenase

e) Enolase

14) Oxamate is a competitive inhibitor of which of the following enzymes ?

a) Hexokinase

b) Phosphofructokinase

c) Glyceraldehyde-3-P dehydrogenase

d) Lactate dehydrogenase

e) Pyruvate dehydrogenase

15)  Which out of the following enzymes of glycolysis is inhibited by Arsenate ?

 a) Hexokinase

b) Phosphofructokinase

c) Glyceraldehyde-3-P dehydrogenase

d) Lactate dehydrogenase

e) Pyruvate dehydrogenase

Answers-

1)-e                2)-b                3)-c                 4)-c                 5)-b                6)-b               

 

7)-d                8)-a                9)-a                10)-d              11)-a              12)-e

 

13)-e              14)-d              15)-c

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1) Which of these enzyme reactions is not irreversible in glycolysis?

a) Hexokinase

b) Glucokinase

c) 3-phosphoglycerate kinase

d) Phosphofructokinase-1

e) Pyruvate kinase

2) Which out of the following statements is not true about aerobic glycolysis ?

a) The rate limiting enzyme is phosphofructokinase-1 which converts fructose-6- phosphate to fructose-1,6-bisphosphate

b) The pathway is inhibited allosterically by fructose-2,6-bisphosphate and AMP

c) The pathway takes place in mitochondria of every cell

d) The pathway produces Pyruvate and NADH

e) The pathway begins with glucokinase or hexokinase

3) The first step in the glycolytic pathway in Liver -

a) Is catalyzed by glucokinase

b) Uses ATP and glucose as substrates

c) Produces glucose-6-phosphate and ADP

d) Is an irreversible step

e) All of the above.

4) Phosphoglycerate kinase functions in carbohydrate metabolism to produce ATP via:

a) Oxidative phosphorylation.

b) Substrate level phosphorylation.

c) Oxidative decarboxylation.

d) Phosphorolysis

e) Oxidative deamination

5). The phosphofructokinase-2 enzyme that transfers a phosphate group to fructose-6-phosphate in glycolysis-

a) Is active in the phosphorylated form

b) Catalyzes a reversible reaction

c) Produces fructose-2,6-bisphosphate as a product

d) Is the rate limiting enzyme for glycolysis

e) Produces ATP as a product.

6). The enzyme that produces NADH from a triose phosphate in the glycolytic pathway-

a) Uses NAD+ and dihydroxyacetone phosphate as substrates

b) Produces 1, 3-Bisphosphoglycerate and NADH

c) Catalyzes irreversible reaction

d) Is called 3-phosphoglycerate kinase

e) Uses FADH2 and glyceraldehyde-3-phosphate as substrates

7). The enzyme that catalyzes first substrate level phosphorylation in glycolysis-

a) Produces 3-phosphoglycerate as a product

b) Produces ADP from AMP

c) Is called glyceraldehyde-3-phosphate dehydrogenase

d) Is called phosphofructokinase

e) Is the rate limiting enzyme of glycolysis.

8). The enzyme that catalyzes the second substrate level phosphorylation of glycolysis-

a) Is called phosphoglyceromutase

b) Produces lactate as a product

c) Uses phosphoenolpyruvate as a substrate

d) Catalyzes a reversible reaction

e) Is stimulated by Glucagon.

9). Which of the following statements about the Lactate dehydrogenase (LDH) reaction is false

a) The enzyme converts pyruvate to lactate

b)The enzyme converts NADH to NAD+

c) The reaction is reversible

d) It is the last enzyme reaction in glycolysis

e) The enzyme is highly active under aerobic conditions

10). The two major factors determining whether a cell oxidizes glucose by aerobic glycolysis or by anaerobic glycolysis are-

a) FADH2 and the number of mitochondria

b) NADH and the ATP/ADP ratio

c) Ca++ and AMP

d) Oxygen pressure and the number of mitochondria

e) Presence of low Glucose and high AMP

11). When glucose is converted to lactate by anaerobic glycolysis, the equivalent of ________ ATPs are derived.  When glucose is completely oxidized to CO2 by glycolysis, Pyruvate dehydrogenase, and the TCA cycle, the equivalent of _______ ATPs are derived.

a) 7;  20

b) 2;  38

c) 7;  32

d)2;  12

e) 7;  25

12).Choose the incorrect statement about the condition ‘When one molecule of glucose is oxidized to 2 molecules of lactate during anaerobic glycolysis’-

a) One molecule of ATP is used by the phosphofructokinase-1 reaction

b) One molecule of ATP is used by either the glucokinase or hexokinase reaction

c) Two molecules of ATP are produced by the Glyceraldehyde -3-P dehydrogenase reaction

d) Two molecules of ATP are produced by the pyruvate kinase reaction

e) No ATP is produced at the level of lactate dehydrogenase reaction.

13). All of the following help to explain some cases of Lactic Acidosis except-

a) High altitude

b) Heart failure

c) Not enough oxygen to satisfy the needs of oxidative phosphorylation

d) Congenital deficiency of liver lactate dehydrogenase

e) Inhibition of the electron transport chain

14) . All of the following are part of the Cori Cycle except-

a) Lactate is the result of anaerobic glycolysis in a number of tissues

b) Lactate is transported to the liver

c) Lactate is converted to glucose in the liver

d) ATP is produced by the conversion of lactate to glucose

e) Glucose is transported from liver to other tissues

15). The ATP/AMP ratio has a major effect upon the rate of ATP production by glycolysis.  ATP and AMP bind to allosteric sites on-

a) Hexokinase

b) Glucokinase

c) Phosphofructokinase-1

d) Phosphofructokinase-2

e) 3-phosphoglycerate kinase

16). Which of the following statements about pyruvate kinase is false -

a) Can convert Phosphoenol pyruvate to pyruvate

b) Is regulated by feed forward regulation

c) Is active in the dephosphorylated form

d) Is also involved in gluconeogenesis

e) Deficiency causes haemolytic anemia.

17). Pasteur effect is due to inhibition of glycolysis by high concentration of -

a) Creatine phosphate

b) ATP

c) ADP

d) AMP

e) Pi

18). In the liver, glucagon causes a decrease in the glycolytic pathway by all of the following mechanisms  except-

a) Increased binding of GTP to G-protein

b) Activation of the cAMP cascade

c) Increased phosphorylation of enzymes by protein kinase A

d) Activation of fructose-2,6-bisphosphatase and inhibition of phosphofructokinase-2

e) Increased binding of fructose-2,6-bisphosphate to phosphofructokinase-1

19). An increased concentration of insulin after meals causes an increase in the rate of  glycolytic pathway by all of the following mechanisms except-

a) Increase uptake of glucose in adipose tissue and muscle

b) Inactivation of the cAMP cascade

c) Increased  dephosphorylation of enzymes activated by protein kinase A

d) Activation of fructose-2,6-bisphosphatase and inhibition of phosphofructokinase-2

e) Induction of Glucokinase and PFK-1

20).During fasting state, the insulin to glucagon ratio drops and all of the following occur except-

a) Protein kinase A will phosphorylate pyruvate kinase

b) The pyruvate kinase step will be activated

c) Protein kinase A will phosphorylate phosphofructokinase-2/fructose-2,6-bisphosphatase

d) The concentration of fructose-2,6-bisphosphate will decrease

e)The liver will not be able to synthesize pyruvate from phosphoenolpyruvate.

21) A high concentration of Glucose-6-P  is inhibitory to which of the following enzymes ?

a) Hexokinase

b) Glucokinase

c) PFK-1

d) PFK-2

e) All of the above,

 

 

Answers-       1)-c,               2)- b,              c)-e,               4)-b,               5)-c,               6)-b,                          

                       

                       7)-a,               8)- c,              9)-e,               10)-b,               11)-b,            12)-c

                       

                        13)-d              14)-d              15)-c              16)-d              17)-b              18)-e

                       

                        19)-d              20)-b              21)-a

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Q.1 – Which of the following substrates derived from adipose tissues contributes to net Gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Glycerol

d) Pyruvate                                                                                                               (    c     )

Q.2 – Which of the following statements is incorrect?

a) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.

b) In anaerobic muscle, pyruvate is converted to lactate.

c) Reduction of pyruvate to lactate generates a coenzyme essential for Glycolysis.

d) Under anaerobic conditions pyruvate does not form because Glycolysis does not occur.

                                                                                                                                                         (     d    )

Q.3- The steps of Glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

a) ATP synthesis.

b) Catalysis by phosphoglycerate kinase.

c) Oxidation of NADH to NAD+.

d) The formation of 1, 3- bisphosphoglycerate.                                                    (    c     )

Q.4 – The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

 a) 2 mol of pentose, 4 mol of NADPH, and 8mol of CO2.

b) 3 mol of pentose, 4 mol of NADPH, and 3mol of CO2.

c) 3 mol of pentose, 6 mol of NADPH, and 3mol of CO2.

d) 4 mol of pentose, 3 mol of NADPH, and 3mol of CO2.                                    (     c    )

Q.5 – How many ATP molecules can be derived from each molecule of acetyl CoA that enters the Krebs’ Cycle?

a) 6

b) 12

c) 18

d) 38                                                                                                                                       (     b    )

Q.6 – All of the following vitamins except one participate in the TCA cycle-

a)Pantothenic acid

b)Lipoic acid

c) Folic acid

d)Riboflavin                                                                                                                        (    c     )

Q.7 – Why Phosphofructokinase rather than hexokinase is the pacemaker of Glycolysis?

a) Glucose 6-phosphate is not solely a glycolytic intermediate

b) Hexokinase has low km for glucose

c) Hexokinase is inhibited by feed back inhibition

d) None of the above                                                                                                       (     a    )

Q.8 - All are correct about pyruvate dehydrogenase complex except one-

a)The formation of acetyl CoA from pyruvate is an irreversible step

b) Pyruvate dehydrogenase is switched off when Acetyl co A is in excess

c)Phosphorylation switches off the activity of the complex.

d) Pyruvate as well as ADP (a signal of low energy charge) inhibits the complex.    (     d    )

Q.9-Cellular isozymes of pyruvate kinase are allosterically inhibited by:

a) High concentrations of AMP.

b) High concentrations of ATP.

c) High concentrations ofFr1,6 bisphosphate.

d) Low concentrations of acetyl-CoA.                                                                       (    b     )

Q.10 – Which of the following is not an intermediate of the citric acid cycle?

a) Acetoacetate

b) Citrate

c) Oxalosuccinate

d) Succinyl-CoA                                                                                                                 (    a     )

Q.11 - In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?

 a) 2-phosphoglycerate

b) Glucose

c) Phosphoenolpyruvate

d) Pyruvate                                                                                                                            (   a    )

Q.12 – Which of the following is a coenzyme  in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

a) ATP

b) Cu2+

c) Heme

d) NAD+                                                                                                                               (     d    )

Q.13 - An enzyme used in both glycolysis and gluconeogenesis is:

a) 3-phosphoglycerate kinase.

b)Glucose 6-phosphatase.

C) Hexokinase.

d)Phosphofructokinase-1.                                                                                            (     a    )

Q.14 – Which of the following statements about the pentose phosphate pathway is incorrect?

 a) It generates 36 mol of ATP per mole of glucose consumed.

b) It generates 6 moles of CO2for each mole of glucose consumed

c) It is a reductive pathway; it consumes NADH.

d) It provides precursors for the synthesis of nucleotides                                 (     c    )

Q.15 – Which of the following enzymes catalyzes a reaction that involves a decarboxylation reaction?

 a)Pyruvate dehydrogenase

b) Isocitrate dehydrogenase

c) α-keto glutarate dehydrogenase

d all of the above                                                                                                              (     d    )

Q.16 -Anaplerotic reactions are those that result in replenishing intermediates in the TCA cycle. Which of the following enzymes catalyzes an Anaplerotic reaction?

a)  Malate dehydrogenase

b) Pyruvate carboxylase

c) Pyruvate kinase

d). Citrate synthase                                                                                                         (      b   )

Q.17- Which statement BEST describes the fate of Propionyl-CoA in mammalian systems?

a) Propionyl-CoA is metabolized via are action sequence that involves vitamin B12 and biotin.

b) Propionyl-CoA is converted to acetyl CoA.

c) Propionyl-CoA and acetyl CoA condense to form a 5 carbon precursor of a TCA cycle intermediate.

d) Propionyl-CoA is oxidized to Malonate and CoA                                              (      a   )

Q.18 – It is very important to feed the baby very soon after birth, because during the first few hours after birth the enzyme Phosphoenolpyruvate carboxykinase is present in very low amounts, and this fact compromises:

a) Gluconeogenesis

b) Glucose phosphorylation

c) Glycogenesis

d) Glycogenolysis                                                                                                                (    a     )

Q.19 – The citric acid cycle is inhibited by which of the following?

 a) Fluoroacetate

b) Aerobic conditions

c) Malic acid

d) Fluorouracil                                                                                                                    (     a    )

Q.20 – Which of the following enzymes is associated with Glycogen synthesis?

a) Amylo- (1, 4->1,6) – transglycosylase

b) Phosphorylase

c) Amylo-1,6-glucosidase

d) Glucose-6- phosphatase                                                                                            (       a  )

Q.21 – A medical student developed hemolytic anemia after taking the oxidizing Antimalarial drug primaquine. This severe reaction is most likely due to

 a) Glucose-6- phosphate dehydrogenase deficiency

b) Concomitant Scurvy

c) Diabetes

d) Glycogen phosphorylase deficiency                                                                     (    a     )

Q.22- Which of the following explains why individuals with hyperlipidemia should minimize their intake of sucrose and high fructose syrup?

 a) Fructose metabolism is faster than glucose

b) After initial modification fructose is cleaved by a specific Enolase

c) Fructose is ultimately converted to galactose

d) Fructose can be phosphorylated by hexokinase in adipose cells                   (    a     )

Q.23-The major glycolytic product produced under normal circumstances by erythrocytes required for unloading of oxygen to the peripheral tissues is

 a) 2,3bisphosphoglycerate

b) 1,3bisphosphoglycerate

d) Lactate                                                                                                                                       (     a    )

c) Pyruvate

Q.24 – Poorly perfused areas exposed to chronic hypoxia have decreased metabolic energy for tissue maintenance and repair an important reason for this is-

 a)  Increased hexokinase activity owing to increased oxidative phosphorylation

b) Decreased ATP production and increased glucose utilization due to an aerobic mode of glycolysis

c) Increased glucose utilization by HMP pathway on changing from anaerobic to aerobic glycolysis

d) Decreased respiratory quotient on changing from carbohydrates to fats as the major fuel                                                                                                                                                              (    b     )

Q.25 – Asians and Native Americans may flush and feel ill after drinking a small amount of ethanol in alcoholic beverages. This reaction is due to genetic variation in an enzyme that metabolizes the liver metabolite of alcohol, which is-

 a) Methanol

b) Acetone

c) Acetaldehyde

d) Glycerol                                                                                                                                    (    c     )

Q.26 – Which one of the following enzymes catalyzes the phosphorylation of the substrate with the use of inorganic phosphate-?

a) Hexokinase

b) Phospho fructokinase

c) Glyceraldehyde-3-phosphate dehydrogenase

d) Phospho glycerate kinase                                                                                                  (     c    )

 


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Q.1-Which of the following enzymes is Thiamine dependent and essential for glucose oxidation in the brain?

a) Pyruvate dehydrogenase complex                  

b) Acetyl co A carboxylase

c) Transaldolase                           

d) Succinyl-co A Thiokinase                                         (     a    )

 

Q.2- The reaction catalyzed by phosphofructo kinase is -

 a) Inhibited by Fructose 2,6 bisphosphate                   

b) Activated by high concentration of ATP

c) A regulatory step of glycolysis   

d) All of the above                                                      (      c   )

 

Q.3- Pyruvate carboxylase requires ————— as a coenzyme.

a) FMN                               

b) Biotin

c) NAD+

d) TPP                                                                        (    b     )

 

Q.4- In erythrocytes the most abundantly found Phospho ester is-

 a) Glucose-6 phosphate                 

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate

d) 2, 3 bisphosphoglycerate                                        (    d     )

 

Q.5- Formation of Galactose-1-P from Galactose is catalyzed by-

a) Hexokinase                              

b) Aldolase      

c) Galactokinase                           

d) Galactose-1-P Uridyl transferase                               (     c    )

 

Q.6- All the following enzymes except one require NADP+ as a coenzyme-

 a) Glucose- 6-phosphate dehydrogenase            

b) Cytosolic Isocitrate dehydrogenase

c) Malic enzyme        

d) Glucose-6-phophatase                                               (     d    )

 

Q.7- Which of the following product of Triglyceride breakdown and subsequent beta oxidation would undergo gluconeogenesis-

a) Propionyl Co A                          

b) Acetyl CoA

c) Aceto acetate                           

d) Beta hydroxy butyrate                                                 (     a    )

 

Q.8 – Which of the following reactions generates ATP?

 a) Glucose to Glucose -6-phosphate         

b) Pyruvate to Lactate

c) Phosphoenol pyruvate to Pyruvate        

d) Glucose- 6 phosphate to fructose-6 phosphate             (   c      )

 

Q.9- Glucose enters muscle cells mostly by:

 a) Simple diffusion

b) Facilitated diffusion using a specific glucose transporter

c) Co-transport with sodium

d) Co-transport with amino acids                                      (     b    )

 

Q.10- Which one of the following compounds is common to both the oxidative phase and the non- oxidative phase of the pentose phosphate pathway?

 a) Xylulose-5- phosphate                         

b) Glucose-6-phosphate

c) Ribulose-5-phosphate                         

d) Glyceraldehyde-3- phosphate                                        (      a     )

 

Q.11- Mc Ardle’s syndrome causes muscle cramps and muscle fatigue with increased muscle glycogen. Which of the following enzyme is deficient?

 a) Hepatic hexokinase                             

b) Muscle Phosphorylase

c) Muscle Debranching enzyme               

d) Muscle Hexokinase                                                         (    b     )

 

Q.12- During starvation, the major source of blood glucose is-

 a) Hepatic Glycogenolysis                       

b) Gluconeogenesis

c)  Muscle Glycogenolysis                       

d) Dietary glucose from intestine                                          (    b     )

 

Q.13- Hexokinase has a considerably lower km for-

 a) Glucose                                    

b) Fructose

c) Galactose

d) Mannose                                                                          (     a    )

 

Q.14- In the fasting state there is considerable release of———–from the muscles.

 a) Glycine                                     

b) Alanine        

c) Valine

d) Glutamic acid                                                                  (     b    )

 

Q.15- A galactosemic child will manifest all except-

 a) Hepatomegaly                           

b) Splenomegaly

c) Cataract

d) Mental retardation                                                            (     b    )

 

Q16- – Which one of the following reactions is unique to gluconeogenesis-?

a) Lactate<———–>Pyruvate

b) Oxaloacetate—->Phosphoenol pyruvate

c) Glucose-6-phosphate—– >Glucose

d) Phosphoenol pyruvate–>Pyruvate                                    (      b   )

 

Q.17- The main stores of glycogen are found in—

 a) Adipose tissues     

b) Skeletal muscles              

c) Brain                              

d) Erythrocytes                                                                    (     b    )

 

Q.18- Succinyl co A is cleaved by-

 a) Succinate dehydrogenase           

b) Succinate Thiokinase

c) Succinate lyase                         

d) Succinate Thioesterase                                                     (    b     )

 

Q.19- Arsenate binds to-

 a)  Free amino end of enzyme                 

b) SH linkages 

c) Free carboxyl end

d) Any of the above                                                               (     b    )

 

Q.20- All are intermediates of glycolysis except-

a) Glucose-6 phosphate                 

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate               

d) Glycerol – 3- phosphate                                                    (     d    )

 

Q.21- The key regulatory enzyme of HMP pathway is-

 a) Glucose- 6-phosphate dehydrogenase  

b) Transaldolase

c) Transketolase                           

d) Glucose-6-phophatase                                                       (     a    )

 

Q.22- The net production of ATP in glycolysis during anaerobic condition is:

 a) 2 from glucose and 3 from glycogen

b) 2 from glucose and 4 from glycogen

c) 3 from glucose and 4 from glycogen

d) 3 from glucose and 2 from glycogen                                   (   a      )

 

Q.23- Which of the followings does not generate free glucose during the enzymatic breakdown of glycogen in skeletal muscles?

 a) Phosphorylase                          

b) α-1-6-amyloglucosidase   

c) Debranching enzyme       

d) glucose-6-phosphatase                                                          (     a    )

 

Q.24- Which of the followings promotes glucose and amino acid uptake by muscle?

a) Adrenaline                                

b) Insulin

c) Glucagon                                  

d) Cortisol                                                                                   (     b    )

 

Q.25- In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be expected to end up principally in:

a) Carbon dioxide                                   

b) Glycogen

c) Phosphoglycerate                               

d) Pyruvate                                                                                   (   a      )

 

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Q.1 – Which of the following substrates derived from adipose tissues contributes to net Gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Glycerol

d) Pyruvate                                                                                                              

 Q.2 – Which of the following statements is incorrect?

 a) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.

b) In anaerobic muscle, pyruvate is converted to lactate.

c) Reduction of pyruvate to lactate generates a coenzyme essential for Glycolysis.

d) Under anaerobic conditions pyruvate does not form because Glycolysis does not occur

Q.3- The steps of Glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:

 a) ATP synthesis.

b) Catalysis by phosphoglycerate kinase.

c) Oxidation of NADH to NAD+.

d) The formation of 1, 3- bisphosphoglycerate.                                                   

Q.4 – The oxidation of 3 mol of glucose by the pentose phosphate pathway may result in the production of:

 a) 2 mol of pentose, 4 mol of NADPH, and 8mol of CO2.

b) 3 mol of pentose, 4 mol of NADPH, and 3mol of CO2.

c) 3 mol of pentose, 6 mol of NADPH, and 3mol of CO2.

d) 4 mol of pentose, 3 mol of NADPH, and 3mol of CO2.                                   

Q.5 – How many ATP molecules can be derived from each molecule of acetyl CoA that enters the Krebs’ Cycle?

 a) 6

b) 12

c) 18

d) 38                                                                                                                                       

 Q.6 – All of the following vitamins except one participate in the TCA cycle-

 a) Pantothenic acid

b) Lipoic acid

c) Folic acid

d) Riboflavin                                                                                                                      

 Q.7 – Why Phosphofructokinase rather than hexokinase is the pace maker of Glycolysis?

 a) Glucose 6-phosphate is not solely a glycolytic intermediate

b) Hexokinase has low km for glucose

c) Hexokinase is inhibited by feed back inhibition

d) None of the above                                                                                                      

 Q.8 - All are correct about pyruvate dehydrogenase complex except one-

a) The formation of acetyl CoA from pyruvate is an irreversible step

b) Pyruvate dehydrogenase is switched off when Acetyl co A is in excess

c) Phosphorylation switches off the activity of the complex.

d) Pyruvate as well as ADP (a signal of low energy charge) inhibits the complex.

Q.9-Cellular isozymes of pyruvate kinase are allosterically inhibited by:

 a) High concentrations of AMP.

b) High concentrations of ATP.

c) High concentrations of Fr1,6 bisphosphate.

d) Low concentrations of acetyl-CoA.                                                                   

 Q.10 – Which of the followings is not an intermediate of the citric acid cycle?

 a) Acetoacetate

b)Citrate

c)  Oxalo succinate

d) Succinyl-CoA                                                                                                                

 Q.11 - In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?

 a) 2-phosphoglycerate

b) Glucose

c) Phosphoenolpyruvate

d) Pyruvate                                                                                                                           

 Q.12 – Which of the following is a coenzyme  in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?

 a) ATP

b) Cu2+

c) Heme

d) NAD+                                                                                                                              

 Q.13 - An enzyme used in both glycolysis and gluconeogenesis is:

a) 3-phosphoglycerate kinase.

b)Glucose 6-phosphatase.

C) Hexokinase.

d)Phosphofructokinase-1.                                                                                          

 Q.14 – Which of the following statements about the pentose phosphate pathway is incorrect?

 a) It generates 36 mol of ATP per mole of glucose consumed.

b) It generates 6 moles of CO2for each mole of glucose consumed

c) It is a reductive pathway; it consumes NADH.

d) It provides precursors for the synthesis of nucleotides                                 

 Q.15 – Which of the following enzymes catalyzes a reaction that involves a decarboxylation reaction?

 a)Pyruvate dehydrogenase

b) Isocitrate dehydrogenase

c) α-keto glutarate dehydrogenase

d) all of the above                                                                                                             

 Q.16 -Anaplerotic reactions are those that result in replenishing intermediates in the TCA cycle. Which of the following enzymes catalyzes an Anaplerotic reaction?

a)   Malate dehydrogenase
b) Pyruvate carboxylase
c) Pyruvate kinase
d) Citrate synthase                                                                                                        

Q.17- Which statement BEST describes the fate of Propionyl-CoA in mammalian systems?

 a) Propionyl-CoA is metabolized via are action sequence that involves vitamin B12 and biotin.

b) Propionyl-CoA is converted to acetyl CoA.

c) Propionyl-CoA and acetyl CoA condense to form a 5 carbon precursor of a TCA cycle intermediate.

d) Propionyl-CoA is oxidized to Malonate and CoA                                            

 

Q.18 – It is very important to feed the baby very soon after birth, because during the first few hours after birth the enzyme Phosphoenolpyruvate carboxykinase is present in very low amounts, and this fact compromises:

a) Gluconeogenesis

b) Glucose phosphorylation

c) Glycogenesis

d) Glycogenolysis                                                                                                                

 Q.19 – The citric acid cycle is inhibited by which of the following?

 a) Fluoroacetate

b) Aerobic conditions

c) Malic acid

d) Fluorouracil                                                                                                                  

 Q.20 – Which of the following enzymes is associated with Glycogen synthesis?

 a) Amylo- (1, 4->1,6) – transglycosylase

b) Phosphorylase

c) Amylo-1,6-glucosidase

d) Glucose-6- phosphatase                                                                                          

 Q.21 – A medical student developed hemolytic anemia after taking the oxidizing Antimalarial drug primaquine. This severe reaction is most likely due to

 a) Glucose-6- phosphate dehydrogenase deficiency

b) Concomitant Scurvy

c) Diabetes

d) Glycogen phosphorylase deficiency                                                                    

 

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Q.1-Which of the following enzymes is Thiamine dependent and essential for glucose oxidation in the brain?

a) Pyruvate dehydrogenase complex                  

b) Acetyl co A carboxylase

c) Transaldolase                           

d) Succinyl-co A Thiokinase                                         

Q.2- The reaction catalyzed by phosphofructo kinase is -

 a) Inhibited by Fructose 2,6 bisphosphate                   

b) Activated by high concentration of ATP

c) A regulatory step of glycolysis   

d) All of the above                                                     

Q.3- Pyruvate carboxylase requires ————— as a coenzyme.

a) FMN                               

b) Biotin

c) NAD+

d) TPP                                                                        

Q.4- In erythrocytes the most abundantly found Phospho ester is-

 a) Glucose-6 phosphate                 

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate

d) 2, 3 bisphosphoglycerate                                        

Q.5- Formation of Galactose-1-P from Galactose is catalyzed by-

a) Hexokinase                              

b) Aldolase      

c) Galactokinase                           

d) Galactose-1-P Uridyl transferase                               

Q.6- All the following enzymes except one require NADP+ as a coenzyme-

 a) Glucose- 6-phosphate dehydrogenase            

b) Cytosolic Isocitrate dehydrogenase

c) Malic enzyme        

d) Glucose-6-phophatase                                               

Q.7- Which of the following product of Triglyceride breakdown and subsequent beta oxidation would undergo gluconeogenesis-

a) Propionyl Co A                          

b) Acetyl CoA

c) Aceto acetate                           

d) Beta hydroxy butyrate                                                 

Q.8 – Which of the following reactions generates ATP?

 a) Glucose to Glucose -6-phosphate         

b) Pyruvate to Lactate

c) Phosphoenol pyruvate to Pyruvate        

d) Glucose- 6 phosphate to fructose-6 phosphate             

Q.9- Glucose enters muscle cells mostly by:

 a) Simple diffusion

b) Facilitated diffusion using a specific glucose transporter

c) Co-transport with sodium

d) Co-transport with amino acids                                      

Q.10- Which one of the following compounds is common to both the oxidative phase and the non- oxidative phase of the pentose phosphate pathway?

 a) Xylulose-5- phosphate                         

b) Glucose-6-phosphate

c) Ribulose-5-phosphate                         

d) Glyceraldehyde-3- phosphate                                        

Q.11- Mc Ardle’s syndrome causes muscle cramps and muscle fatigue with increased muscle glycogen. Which of the following enzyme is deficient?

 a) Hepatic hexokinase                             

b) Muscle Phosphorylase

c) Muscle Debranching enzyme               

d) Muscle Hexokinase                                                         

Q.12- During starvation, the major source of blood glucose is-

 a) Hepatic Glycogenolysis                       

b) Gluconeogenesis

c)  Muscle Glycogenolysis                       

d) Dietary glucose from intestine                                          

Q.13- Hexokinase has a considerably lower km for-

 a) Glucose                                    

b) Fructose

c) Galactose

d) Mannose                                                                          

Q.14- In the fasting state there is considerable release of———–from the muscles.

 a) Glycine                                     

b) Alanine        

c) Valine

d) Glutamic acid                                                                  

Q.15- A galactosemic child will manifest all except-

 a) Hepatomegaly                           

b) Splenomegaly

c) Cataract

d) Mental retardation                                                            

Q.16- – Which one of the following reactions is unique to gluconeogenesis-?

a) Lactate<———–>Pyruvate

b) Oxaloacetate—->Phosphoenol pyruvate

c) Glucose-6-phosphate—– >Glucose

d) Phosphoenol pyruvate–>Pyruvate                                    

Q.17- The main stores of glycogen are found in—

 a) Adipose tissues     

b) Skeletal muscles              

c) Brain                              

d) Erythrocytes                                                                    

Q.18- Succinyl co A is cleaved by-

 a) Succinate dehydrogenase           

b) Succinate Thiokinase

c) Succinate lyase                         

d) Succinate Thioesterase                                                    

Q.19- Arsenate binds to-

 a)  Free amino end of enzyme                 

b) SH linkages 

c) Free carboxyl end

d) Any of the above                                                               

Q.20- All are intermediates of glycolysis except-

a) Glucose-6 phosphate                 

b) Fructose 1, 6 bisphosphate

c) Fructose-6- phosphate               

d) Glycerol – 3- phosphate                                                   

Q.21- The key regulatory enzyme of HMP pathway is-

 a) Glucose- 6-phosphate dehydrogenase  

b) Transaldolase

c) Transketolase                           

d) Glucose-6-phophatase                                                       

Q.22- The net production of ATP in glycolysis during anaerobic condition is:

 a) 2 from glucose and 3 from glycogen

b) 2 from glucose and 4 from glycogen

c) 3 from glucose and 4 from glycogen

d) 3 from glucose and 2 from glycogen                                  

Q.23- Which of the followings does not generate free glucose during the enzymatic breakdown of glycogen in skeletal muscles?

a) Phosphorylase                          

b) α-1-6-amyloglucosidase   

c) Debranching enzyme       

d) glucose-6-phosphatase                                                          

Q.24- Which of the followings promotes glucose and amino acid uptake by muscle?

a) Adrenaline                                

b) Insulin

c) Glucagon                                  

d) Cortisol                                                                                   

Q.25- In a tissue that metabolizes glucose via the pentose phosphate pathway, C-1 of glucose would be expected to end up principally in:

a) Carbon dioxide                                   

b) Glycogen

c) Phosphoglycerate                               

d) Pyruvate                                                                                  

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1)   The answer is –b) Beta hydroxy Butyrate,  a ketone body. Ketone bodies serve as alternative fuel for brain during prolonged fasting or starvation. Fatty acids due to long hydrophobic chain can not cross blood brain barrier. Glycerol is a substrate of gluconeogenesis. In fact during prolonged fasting this is the only substrate left to provide glucose through pathway of gluconeogenesis. It can be oxidized through glycolysis after phosphorylation. Beta carotene is a provitamin; it is not a source of energy.

 2)   The answer is –a) Fatty acid break down provides Acetyl co A that serves as a precursor for ketone bodies. In Diabetes Mellitus glucose utilization is impaired due to absolute or relative insulin deficiency. Fatty acid breakdown occurs to provide energy and the resultant excessive Acetyl co A enters the pathway of ketogenesis. Protein breakdown provides amino acids, 6 amino acids are ketogenic, while 14 are glucogenic. Hence protein breakdown contributes only a little towards formation of Acetyl co A. The major contribution is through fatty acid breakdown. Glycogenolysis and Gluconeogenesis produce glucose only.

 3)   The answer is –a) Galactosemia. The clinical manifestations are typical of classical Galactosemia. Bilateral cataract rules out the possibility of Von Gierke’s disease and hereditary fructose intolerance, although other symptoms are there in both these diseases. In juvenile diabetes mellitus, jaundice and hepatomegaly are not observed.

 4)   The answer is-d)- Lactate, the end product of glycolysis in erythrocytes and  during intense exercise in skeletal muscles ,is mobilized through Cori cycle to  liver to provide glucose by the process of gluconeogenesis. (Erythrocytes lack mitochondria so the end product of glycolysis is always lactate.  The mode of glycolysis during intense exercise is anaerobic; hence lactate is formed as a result of glycolysis.

Alanine is transported to liver through Glucose Alanine cycle. Glycerol is also similarly transported but not from the erythrocytes or skeletal muscles, rather from the adipose tissues. Glycerol is a waste product in adipose tissues since without phosphorylation it can not be utilized and the phosphorylating enzyme glycerol kinase is absent in adipose tissues.

 5)   The answer is-b) Branching enzyme. During the process of glycogen synthesis, branching enzyme creates branch points and further elongation is carried out by Glycogen synthase . In its deficiency stored glycogen is abnormal in chemistry, in the form of long polysaccharide chains with few branch points, resembling the structure of Amylopectin, thus this defect is also called Amylopectinosis. Alpha Amylase is an enzyme for digestion of starch and glycogen. Debranching enzyme deficiency results in the accumulation of abnormal glycogen, There is inability to remove the branch points, the resultant structure resembles Limit dextrin , thus it is also called Limit dextrinosis

 6)   The answer is-d) The hydrolysis of starch is catalyzed by salivary and pancreatic amylases, which catalyze random hydrolysis of alpha (1- 4) glycoside bonds, yielding dextrins, and further hydrolysis yields a mixture of glucose, maltose, isomaltose (from the branch points in amylopectin) and maltotriose.

 7)   The answer is- c) Palmitate,  a fatty acid with 16 carbon atoms, is not a substrate for gluconeogenesis. Even chain fatty acids, predominantly present in our body, yield Acetyl co A upon oxidation, which can not contribute towards gluconeogenesis.  The Pyruvate to Acetyl co A conversion is irreversible and moreover both  of the carbon atoms of Acetyl co A are lost in the TCA cycle in the form of CO2.Oddchain fatty acid do act as substrates of gluconeogenesis, since propionyl co A the product of their oxidation can enter TCA cycle through formation of Succinyl co A, hence  can contribute towards Glucose production.

 8)   The answer is-d) Hypoglycemic coma occurs as a result of insulin over dosage in Type 1diabetes Mellitus.  It is not observed in Type 2 diabetes. Weight gain can occur in both types, it is the result of treatment with insulin or certain hypoglycemic drugs.

 9)   The answer is- a) Hexokinase is a non specific enzyme, it can phosphorylate fructose as well as other sugars but it has high km(low affinity) for fructose.  Glucose is the true substrate for this enzyme.Fructose-6-phosphatethe end product of Hexokinase reaction can enter glycolytic pathway to be utilized further, so it does not accumulate to produce the toxic effects. Liver Aldolase (Aldolase B) cleaves Fructose-1-P only, the product of fructokinase catalyzed reaction.  Aldolase A, present in all the cells of the body cleaves Fructose 1,6 bisphosphate, the product of PFK-1 catalyzed reaction of glycolysis.

 10) The answer is- b) Free glucose is released by the action of α-1-6-amyloglucosidaseenzyme, a component of debranching enzyme. Debranching enzyme has two components. α-[1 4] -α-[1 4] Glucan transferase and α-1-6-amyloglucosidase.Glucan transferase shifts the trisaccharide on a branch bound by α-[1- 4]  linkage to the straight chain and joins by α-[1 4] linkage. The exposed branch point is hydrolyzed by α-1-6-amyloglucosidase enzyme. Both components are present on the same polypeptide chain. Glucose-6- phosphatase does produce free glucose but it is absent in skeletal muscles.

 

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1) A 30-year-old man has been fasting for religious reason for several days.  His brain has reduced its need for glucose by using which of the following substances as an alternate source of energy?

a) Fatty acids

b) Beta hydroxy butyrate

c) Glycerol

d) Beta carotene

2) A 7-year-old girl is brought to the emergency department by her parents with complaints of severe polyuria and Polydipsia. Laboratory examination reveals ketones in her urine. Which of the followings is the most likely source of ketones?

a) Fatty acid breakdown

b) Protein break down

c) Glycogenolysis

d) Gluconeogenesis.

3) A breast-fed infant began to vomit frequently and lose weight. Several days later she developed jaundice, hepatomegaly and bilateral cataract. What is the possible cause for these symptoms? 

a) Galactosemia

b) Von-Gierke’s disease

c) Juvenile diabetes Mellitus

d) Hereditary fructose intolerance

4) The major metabolic product produced under normal circumstances by erythrocytes and by muscle cells during intense exercise is recycled through liver in the Cori cycle. The metabolite is-

a) Oxaloacetate

b) Alanine

c) Glycerol

d) Lactate

5) A 3-month-old infant presents with hepatosplenomegaly and failure to thrive. A liver biopsy reveals glycogen with an abnormal, amylopectin like structure with long outer chains and missing branches.  Which of the following enzymes would most likely be deficient?

a) Alpha Amylase

b) Branching enzyme

c)  Debranching enzyme

d) Glycogen phosphorylase                  

6) Prior to a race, many marathon runners will try to increase their glycogen concentrations by loading up with foods with a high starch content, such as pasta. Alpha amylase secreted by the pancreas  will digest the starch into which of the following major products?

a) Amylose, amylopectin, and maltose

b) Glucose, galactose, and fructose

c) Glucose, sucrose, and maltotriose

d) Limit dextrins, maltose, and maltotriose

7) Which of the following substrates cannot contribute to net Gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Palmitate

d) Pyruvate

8) Which of the following complications is less likely to occur in type II diabetics, as opposed to type I diabetics?

a) Retinopathy

b) Weight gain

c) Cardiovascular disease

d) Hypoglycemic coma

9) Familial fructokinase deficiency causes no symptoms because

a) Hexokinase can phosphorylate fructose

b) Liver Aldolase can metabolize it

c) Excess fructose does not escape in to urine

d) Excess fructose is excreted through feces.

10) Which of the followings generates free glucose during the enzymatic breakdown of glycogen in skeletal muscles?

a) Phosphorylase

b) α-1-6-amyloglucosidase

c) Debranching enzyme

d) Glucose-6-phosphatase

 

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