Main Menu

Advertisement

Multiple Choice Questions

1. Which of the following are the ketone bodies?

a) Acetyl co A and Propionyl co A

b) Lecithin and Lysolecithin

c) Acetoacetate and Betahydroxy butyrate

d) Pyruvate and lactate

e) Succinyl co A and succinate

2. The enzyme ‘Thiolase’ catalyzes the conversion of-

a) 2 Acetyl co A to Acetoacetyl co A

b) Acetyl co A to Malonyl co A

c) Fatty acid to Fatty Acyl co A

d) Succinyl co A to succinate

e) Propionyl co A to D- Methyl malonyl co A

3. In contrast to secondary bile salts, which of the following is characteristic of primary bile salts?

a) Are hydroxylated at carbon 7

b) Have an oxidized side chain

c) Form co A derivatives

d) Can be conjugated to Glycine or Taurine

e) Are reabsorbed in the intestine

4. Which of the following statements best describes the fatty acid synthase complex?

a) Is a dimer of dissimilar subunits

b) is composed of 7 different proteins

c) Dissociates in to eight different proteins

d) Catalyzes 8 different enzymatic steps

e) Is composed of covalently linked enzymes

5. The end product of fatty acid synthesis in mammals is –

a) Arachidonic acid

b) Linoleic acid

c) Stearic acid

d) Palmitic acid

e) Erucic acid

6. Which enzyme often mal functions in diseases associated with the symptoms of high blood triglyceride levels and Steatorrhea?

a) Phospholipase D

b) Lipoprotein lipase

c) Thiokinase

d) Acetyl co A carboxylase

e) Pancreatic lipase

7. Which enzyme is an allosteric regulator of another enzyme on the list ?

a) Acetyl co A carboxylase

b) Pancreatic lipase

c) Carnitine acyl transferase-1

d) Acetyl transacylase

e) Keto acyl synthase

8. A new-born has severe respiratory problems. Over the next few days it is observed that the baby has severe muscle problems, demonstrates little development, and has neurological problems. A liver biopsy reveals a very low level of acetyl co A carboxylase, but normal levels of the enzymes of glycolysis and gluconeogenesis, the citric acid cycle, and the pentose phosphate pathway. What is the most likely cause of infant’s respiratory problems ?

a) Low level of phosphatidyl choline

b) Biotin deficiency

c) Ketoacidosis

d) High level of citrate

e) Glycogen depletion

9. In cystic fibrosis, the pancreatic ducts become obstructed by viscous mucus. Consequently digestion of which of the following substances would be most impaired ?

a) Starch

b) Glycogen

c) Cellulose

d) Lipids

e) Maltose

10. Insulin promotes which of the following ?

a) Transport of glucose in to cells

b) Conversion of Triacyl glycerol to diacylglycerol

c) Fatty acid oxidation

d) Decreased activity of lipoprotein lipase

e) Increased blood glucose level

11.Dicarboxylic aciduria is a defect associated with impaired-

a) Alpha oxidation of fatty acids

b) Beta oxidation of fatty acids

c) Fatty acid synthesis

d) Omega oxidation of fatty acids

e) de novo cholesterol synthesis

12. In alpha oxidation which of the following products is released ?

a) Co A

b) CO2

c) H2O

d) Acetyl co A

e) Malonyl co A

13. A 2 year -old boy has been diagnosed with Zellweger syndrome, a disorder caused by malformation of peroxisomes. The oxidation of which of the following fatty acids is impaired in this defect ?

a) Palmitic acid

b) Unsaturated fatty acids

c) Very long chain fatty acids

d) Branched hail fatty acids

e) Cyclic fatty acids

14. A 15-year-old female has been diagnosed with anorexia nervosa. In this patient breakdown of fatty acids is required to provide energy. Prior to fatty acid oxidation activation of fatty acid takes place in the cytosol. Which of the following is the product of fatty acid activation ?

a) ATP

b) Co A

c) Fatty acyl Co A

d) Carnitine

e) Malonyl co A

15. Tangier disease is a disease of cholesterol transport. The first case was identified in a patient who lived on the island of Tangier and who had characteristic  orange-colored tonsils, a very low HDL and an enlarged liver and spleen. Due to mutation in a transport protein, cholesterol cannot properly exit the cell to bind to apo A. Which of the following is the most important risk factor for such patients due to deceased level of HDL ?

a) Diabetes mellitus

b) Atherosclerosis

c) Cataract

d) Ketosis

e) Fatty liver

16. A 40 -year-old man presents with severe pain in his legs upon walking. He is diagnosed with atherosclerotic plaques in the arteries of his legs. High levels of cholesterol and LDL contribute to the formation of atherosclerosis. The oxidized form of LDL triggers the process of atherosclerosis. Which of the following is the most important structural component of LDL?

a) Apo B48

b) Apo B 100

c) Apo A

d) Apo C

e) Apo E

17. A 30 -year-old man has been diagnosed with familial hypercholesterolemia, a disorder caused by a deficiency of LDL receptors. Which of the following statements best describes the status of these patients ?

a) Serum cholesterol decreases

b) Excessive cholesterol is released by HDL

c) Cholesterol synthesis by hepatocytes is increased

d) Number of LDL receptors on the surface of hepatocytes increase

e) After binding to LDL receptors, LDL is rapidly degraded

18. A 25-year-old woman presents with a low red blood cell count, corneal opacities and kidney insufficiency. She is diagnosed with Lecithin :Cholesterol acyl transferase(LCAT) deficiency. Which of the following is LCAT involved in ?

a) Converting cholesterol to cholesteryl ester

b) Transfer of cholesterol to other lipoproteins

c)  Degradation of HDL in liver

d) Degradation of chylomicrons

e) Decreased uptake of cholesterol by hepatocytes

19. A 34-year-old female has been diagnosed with type 1 hyperlipidemia. Which of the following lipoprotein concentration is elevated in such disorder ?

a) VLDL

b) IDL

c) LDL

d) Chylomicrons

e) All of the above

20. Abundance of which of the following inhibits beta oxidation of fatty acids ?

a) ATP

b) Long chain fatty acids

c) Malonyl co A

d) Citrate

e) Acetyl co A

Key to answers

1) – c

2)- a

3)- a

4)-e

5)- d

6)- e

7)- a

8)- a

9)- d

10)- a

11)- b

12)- b

13)- c

14)- c

15)-b

16)- b

17)- c

18)- a

19)- d

20)- c

Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

1) Which of the following is the best marker for the diagnosis of Acute pancreatitis?

a) Lactase

b) Amylase

c) Cholesteryl esterase

d) Υ- Glutamyl trans peptidase

e) Sucrase

2) A gall stone that blocked the upper part of the bile duct would cause an –

a) Increased  formation of chylomicron

b) Increased  recycling of bile salts

c) Increased excretion of bile salts

d) Decreased excretion of fats in the feces

e) Incomplete lipid digestion and absorption

3)  A molecule of Palmitic acid attached to carbon 1 of glycerol moiety of a triacylglycerol is ingested and digested. Which of the following molecular complexes in the blood carries the palmitate residue from the lumen of the gut to the surface of the gut epithelial cell?

a) VLDL

b) LDL

c) IDL

d) HDL

e) Bile salt

4) Which of the following supplies all the carbon atoms that are needed for de novo synthesis of cholesterol?

a) Glucose

b) Acetyl co A

c) Malonyl co A

d) Succinyl co A

e) Citrate

5) Which of the following is not needed for the de novo synthesis of fatty acids?

a) NADPH

b) Acetyl co A

c) Bicarbonate

d) ATP

e) Folic acid

6) Glycerol produced from hydrolysis of triglycerides in adipose tissue is a waste product, since it has to be in glycerol-3-P form and the enzyme for phosphorylation, glycerol kinase is absent in the adipose tissue. Glycerol -3-P can still be produced in the adipose tissue through interconversion of one of the glycolytic intermediate. Which of the following glycolytic intermediate can be used for the synthesis of glycerol-3-P?

a) Phospho enol pyruvate

b) 1, 3 Bisphosphoglycerate

c) Dihydroxyacetone phosphate

d) Fructose 1, 6 bisphosphate

e) 2, phosphoglycerate

7) Which of the following enzymes is required for releasing the newly synthesized fatty acid from the fatty acid synthase complex?

a) Thiolase

b) Thiophorase

c) Thioesterase

d) Thiokinase

e) Hydratase

8) Which of the following is the key regulatory enzyme of fatty acid synthesis?

a) ATP citrate lyase

b) Keto acyl synthase

c) Acetyl transacylase

d) Acetyl co A carboxylase

e) Thiolase

9) The “microsomal system “elongates saturated and unsaturated fatty acyl-CoAs (from C10 upward) by two carbons, using-

a) Malonyl co A

b) Acetyl co A

c) Succinate

d) Pyruvate

e) Citrate

10) Which of the following is a break down product of odd chain fatty acids?

a) Acetyl co A only

b) Acetyl co A and Butyryl co A

c) Acetyl co A and Propionyl co A

d) Propionyl co A only

e) Butyryl co A only

11) Lipogenesis is increased when sucrose is fed instead of glucose because-

a) Sucrose is digested and absorbed rapidly

b) Sucrose metabolism causes release of insulin

c) Fructose, the hydrolytic product activates acetyl co A carboxylase

d) Fructose bypasses the phosphofructokinase control point in glycolysis and floods the pathway

e) All of the above

12) An obese, 40- year-old woman, who recently underwent gastric bypass surgery, presents with severe vomiting due to rapid intake of large quantities of food, which must be avoided after gastric bypass surgery. She had successfully lost 10 pounds over the last month after the surgery due to mobilization of fat stores to provide acetyl co A and energy. When Stearic acid is oxidized, how many Acetyl co A are produced?

a) 1

b) 8

c) 9

d) 2

e) 10

13) A 4 month -old infant presents with a seizure. His mother reports that her infant has been irritable and lethargic over the past several days. The infant is found to have a profoundly low serum glucose and ketone body level. The infant is diagnosed with medium chain acyl co A dehydrogenase deficiency. What is the biochemical basis of infant’s symptoms?

a) Beta oxidation of fatty acid is impaired

b) Fatty acid synthesis is impaired

c) Adipolysis is inhibited

d) TCA cycle is inhibited

e) Pyruvate to acetyl co A conversion is inhibited

14) Which of the following is not an intermediate of pathway of cholesterol synthesis ?

a) Mevalonate

b) Squalene

c) Lanosterol

d) Desmosterol

e) 7- dehydro cholesterol

15) A 45 -year-old female presents with pain in the right hypochondrium radiating towards shoulder and back. She is diagnosed with acute cholecystitis (inflammation of the gall bladder).The gall stones can obstruct the gall bladder, leading to an inadequate concentration of bile salts in the intestine. Which of the following statements best describes the bile salts?

a) Squalene and Lanosterol are examples of primary bile salts

b) Bile salts are required for transportation of lipids from intestine to liver

c) 95% of the bile salts are excreted in the feces per day

d) They are required for digestion and absorption of lipids

e) Bile salts are synthesized from glycine and taurine

16) Which of the following apo proteins is an activator of LCAT?

a) Apo A

b) Apo B

c) Apo C II

d) Apo A- I

e) Apo E

17) In Abetalipoproteinemia (a rare disease), lipoproteins containing apo B are not formed and lipid droplets accumulate in the intestine and liver. Which of the following lipoproteins does not contain Apo B protein?

a) LDL

b) IDL

c) HDL

d) Chylomicrons

e) Lp (a)

18) Which of the following statements best describes cholesterol ester transfer protein (CETP)?

a) It converts cholesterol from LDL to cholesterol esters

b) It is the major protein of Chylomicrons

c) It exchanges cholesterol esters from HDL for other lipids

d) It acts as a ligand for LDL receptors

e) It transfers cholesteryl esters from peripheral tissues to HDL

19) An infant is born prematurely at 28 weeks and has developed increasing difficulty in breathing. His skin starts to turn blue from lack of oxygen(cyanosis).He is diagnosed with Respiratory distress syndrome due to deficiency of lung surfactant . Which of the following is the phospholipid of primary importance in surfactant?

a) Dipalmitoyl phosphatidyl choline

b) Dipalmitoyl phosphatidyl ethanolamine

c) Dipalmitoyl phosphoglyceride

d) Dipalmitoyl phosphatidyl Inositol

e) Dipalmitoyl phosphatidyl serine

20) A male infant is born with ambiguous genitalia (from lack of androgens such as testosterone) and several salt wasting (due to lack of aldosterone). He is diagnosed with 3-β-hydroxylase deficiency. Testosterone is produced from which of the following compounds?

a) Arachidonic acid

b) Linolenic acid

c) Glucose

d) Cholesterol

e) Acetyl co A

21) A 20- year-old woman has a myocardial infarct and is given an Aspirin to chew. Taking aspirin has been shown to be cardio protective in myocardial infarction. Aspirin is a non steroidal anti inflammatory drug that inhibits cyclo oxygenase enzyme (COX). Cyclo oxygenase is required for the production of which of these?

a)Thromboxane from Arachidonic acid

b) Leukotrienes from Arachidonic acid

c) Arachidonic acid from Linoleic acid

d) Release of Arachidonic acid from membrane Phospholipids

e) Hydroperoxy eicosa tetra enoic acid (HPETEs) from Arachidonic acid

 

Key to answers

1) – b

2) – e

3) – e

4) – b

5) – e

6) – c

7) -c

8) – d

9) – a

10) – c

11) – d

12) – c

13) – a

14) – e

15) – d

16) – d

17) – c

18) – c

19) – a

20) – d

21)  – a

Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

1)- Cholesterol is a precursor of all of the followings  except-

a) Taurocholate

b) Glycocholate

c) Calcitriol

d) Corticosteroids

e) Calcitonin.

2)- All the 27 carbon atoms of cholesterol are derived from-

a) Acetyl co A

b) Acetoacetyl co A

c) Propionyl co A

d) Succinyl co A

e) Malonyl co A

3)- Cytosolic  3-hydroxy-3-methylglutaryl CoA (HMG CoA) is reduced to Mevalonate for the synthesis of cholesterol, the enzyme catalyzing this irreversible step is-

a) Thiolase

b) Thioesterase

c) Thiophorase

d) HMG Co A synthase

e) HMG Co A reductase.

4)- Which out of the following statements best describes about ACAT (Acyl co A cholesterol acyl transferase) ?

a) Required for reverse cholesterol transport

b) Rate limiting enzyme for bile acid synthesis

c) Requires mono unsaturated fatty acid for esterification of cholesterol

d) Required for degradation of chylomicrons and VLDL

e) It is a major component of HDL.

5)- Which out of the following statements is incorrect about bile salts ?

a) Major constituent of bile

b) Solubilize dietary lipids

c) Major breakdown products of cholesterol

d) Taurocholate is the major bile salt.

e) Bile salts are highly effective detergents

6) – A deficiency of apoprotein C-ll results in the disease hyperlipoproteinemia type I, in which there is a significant increase in the concentration of plasma triacylglycerol. Which of the following is true about the condition?

a) VLDL and HDL increase

b) Plasma appears milky

c) There is a risk for premature IHD

d) Serum total cholesterol increases

e) Apo C-II acts as an activator of LCAT enzyme.

7)- Which of the following lipid lowering drugs act by inhibiting the absorption of dietary cholesterol ?

a) Statins

b) Ezetimibe

c) Colestipol

d) Clofibrate

e) Cholestyramine

8)- In familial hypercholesterolemia, cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma. Of particular concern is the oxidation of the excess blood LDL to form oxidized LDL (oxLDL). The oxLDL is taken up by immune-system cells called macrophages, which become engorged to form foam cells. Which statement best describes the formation of foam cells?

a) LDL receptors on peripheral cells are upregulated

b) LDL receptors for modified LDL (Ox LDL) are not down regulated

c) LDL enters by pinocytosis to form foam cells

d) There is increased de no synthesis of cholesterol

e) Cholesterol is not extracted from macrophages by HDL

9)- A patient presents with very high levels of serum cholesterol. After a series of tests, it is concluded that the patient has high circulating levels of LDL cholesterol, but has normal levels of the liver LDL receptor. One possible explanation for this observation is which of the following?

a) The patient has a mutated form of apoprotein B-100.

b) The inability to selectively remove cholesterol from the LDL complex.

c) The absence of the enzyme lipoprotein lipase.

d) Decreased levels of acyl-CoA: cholesterol acyl transferase.

e) Altered phosphorylation of the LDL receptor.

10)- A patient presents in your office with very high levels of serum cholesterol. He states that he has tried to follow the diet and exercise regimen you gave him last year. You decide that this patient would benefit from a drug such as Lipitor (atorvastatin). This class of drugs is effective in treating hypercholesterolemia because it has what effect?

a) Stimulates phosphorylation of the β-hydroxy-β-methyl glutaryl- CoA reductase enzyme

b) Decreases the stability of the β-hydroxy-β-methyl glutaryl-CoA reductase protein

c) Binds cholesterol preventing it from being absorbed by the intestine

d) Directly prevents the deposition of cholesterol on artery walls

e) Inhibits the enzyme β-hydroxy-β-methyl glutaryl-CoA reductase.

11)- Free cholesterol can affect cholesterol metabolism in the body by inhibiting cholesterol biosynthesis. The step at which free cholesterol inhibits its biosynthesis is by inhibiting which of the following processes?

a) Cyclizing of squalene to form lanosterol

b) Reduction of 7-dehydrocholesterol to form cholesterol

c)  Formation of mevalonate from hydroxymethylglutaryl-CoA

d)  Kinase that phosphorylates hydroxymethylglutaryl-CoA reductase

e) Condensation of acetyl-CoA and acetoacetyl-CoA to form hydroxymethyl glutaryl-CoA

12)- A patient with hereditary type I hyperlipidemia presents with elevated levels of chylomicrons and VLDL triglycerides in the blood. The main function of the chylomicrons in circulation is to do which of the following?

a) Transport lipids from the liver

b) Transport dietary lipids from the intestine to target tissues

c) Transport cholesterol from IDL to LDL

d) Act as a receptor for triacylglycerols in the liver

e)  Bind cholesterol esters exclusively

13)- The modification to bile salts that increases the working pH range and amphipathic nature of bile salts is

a) 7α-Hydroxylation

b) Dehydroxylation by intestinal bacteria

c)  Esterification

d)  Conjugation to taurine or glycine

e) Formation of salts with sodium and Potassium.

14)- A 53-year-old male patient with elevated levels of low-density lipoprotein (LDL) cholesterol, signs of premature cholesterol gallstone disease and substantially elevated triglycerides visited his physician for a follow-up to check his current status. The patient had received various statin, HMG-CoA-reductase inhibitors therapies for the past 2 years. However, after blood work done at this follow-up visit, complications had still not subsided. This patient has similar problems as two of his siblings.

Which of the following best explains this patients dyslipidemia?

a) An influx of abnormal phospholipids in the gallbladder as a result of ileal disease

b)  A loss of HMG-CoA reductase function

c)  A loss of CYP7A1 (cholesterol 7-α-hydroxylase) function

d)  Elevated levels of ACAT

e) Less number of LDL receptors

15)- A patient has been on combination statin and Cholestyramine therapy to lower his serum cholesterol levels. Prior to any surgery, this patient would be well advised to be supplemented with which of the following?

a)  Vitamin A

b)  Vitamin B12

c)  Vitamin C

d) Vitamin K

e) Linolenic acid.

17)- A 18-year-old male with sickle-cell anemia develops severe right upper-abdominal pain radiating to his lower right chest and his right flank 36 hours prior to admission to the ER. He also reports that his urine is the color of iced tea and his stool now has a light clay color. On examination, his temperature is slightly elevated, and heart rate is rapid. He is exquisitely tender to pressure over his right upper abdomen. The sclerae of his eyes are slightly  yellowish in color.

What is the most likely cause of this patient’s symptoms?

a) A cholesterol-rich gallstone

b)  A defect in the synthesis of bile acids

c)  A defect in heme synthesis

d)  A gallstone rich in calcium bilirubinate

e)  A sickle-cell crisis brought on by overexertion

18) Which of the following compounds directly inhibits the expression of the HMG-CoA reductase gene?

a)  Squalene

b) HMG-CoA

c)  Lanosterol

d)  Isopentenyl pyrophosphate

e)  Cholesterol

19) Which of the following vitamins can be used in high doses to treat hypercholesterolemia?

a)  Niacin

b)  Riboflavin

c)  Pyridoxine

d)  Folic acid

e) Thiamine.

20) A teenage boy presents with moderate to severe epigastric pain. Physical examination reveals extensive eruptive xanthomas and hepatosplenomegaly. A blood sample reveals milky plasma. Which of the following is the most likely lipoprotein to be elevated in this patient ‘s plasma?

a) Chylomicrons

b) Chylomicron remnants

c)  HDL

d)  IDL

e)  LDL

21) – A 25-year-old female was referred to a lipid research center for investigation of moderate hypertriglyceridemia because the plasma lipid and lipoprotein profiles showed abnormalities. Both HDL and LDL were more buoyant and showed elevations in TG content with the mass of TG approximately the same as that of cholesterol. A deficiency in which of the following is the most likely cause of this patient’ s lipid abnormality?

a)  Lecithin-cholesterol acyltransferase (LCAT)

b)  Lipoprotein lipase

c)  Apoprotein C-II

d)  Hepatic lipase

e) Apoprotein B-100

22)-  Laboratory results for a patient with uncontrolled Type I diabetes mellitus reveal hyperglycemia (634 mg/dL) and hypertriglyceridemia (498 mg/dL). The most likely cause of the hypertriglyceridemia in this patient is which of the following?

a) Deficiency in apoprotein C-II

b) Increased hepatic triglyceride synthesis

c)  Decreased lipoprotein lipase activity

d)  Deficiency in LDL receptors

e)  Absence of hormone-sensitive lipase

 

Key to answers

1)-e,      2)-a,       3)-e,      4)-c,       5)-d,      6)-b,      7)-b,      8)-b,      9)-a,       10)-e,    11)-c,     12)-b, 13)-d,    14)-c,     15)-d,    16)-d,    17)-d,    18)-e,    19)- a,   20)-a,    21)-d,    22)-c

Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

Q.1 – A gall stone that blocked the upper part of the bile duct would cause increase in which of the followings ?

a) The excretion of fats in the feces

b) Formation of chylomicrons

c) Excretion of bile salts

d) Conjugation of bile acids

e) Recycling of bile salts

Q.2- An 8-year-old boy presents with orange-colored tonsils, a very low HDL levels and an enlarged liver and spleen. He is diagnosed with Tangier disease. Tangier disease is a disease of  cholesterol transport, such that cholesterol  cannot properly exit the cell and form HDL. Which of the following statements best describes HDL ?

a) It is produced in skeletal muscles

b) It scavenges cholesterol from cell membranes

c) Its major protein is apo E

d) It is formed when VLDL is acted upon by lipoprotein lipase

e) It activates ACAT

Q3- In contrast to secondary bile salts, which of the following is not a characteristic of primary bile salts

a) Are hydroxylated at position 17

b) Have an oxidized side chain

c) Can be conjugated to Taurine and glycine

d) Are reabsorbed in the intestine

e) Formed from cholyl co A .

Q.4-In the conversion of cholesterol to bile salts, which of the following statements best describes the process ?

a) Carbon 8 is hydroxylated

b) The side chain can be conjugated with glycine or Taurine

c) The double bond is oxidized

d) The hydroxyl group at 3 carbon remains in the beta position

e) It occurs in the bile duct.

Q.5- Which of the following statements best describes low density lipoprotein  (LDL) ?

a) It has the most Triacyl glycerol and the least protein

b) It has more Triacyl glycerol than very low density lipoprotein(VLDL)

c) It has the lowest Triacyl glycerol content

d) It has the highest protein content

e) It has the highest cholesterol content.

Q.6- Which of the following apoproteins is an activator of lipoprotein lipase ?

a) Apo A

b) Apo B

c) Apo C II

d) Apo D

e) Apo E

Q.7- Which of the following lipoproteins are the major carriers of Triacyl glycerol ?

a) IDL and LDL

b) VLDL and LDL

c) Chylomicrons and VLDL

d) HDL and VLDL

e) Chylomicrons and HDL.

Q.8- A 60 -year-old woman presents with chest pain radiating to her left arm. She is diagnosed with Myocardial infarction and is prescribed a statin medication. Statins inhibit HMG Co A reductase. How does inhibition of HMG Co A reductase cause lowering of cholesterol and LDL levels ?

a) It increase serum level of HDL

b) It decreases serum level of LDL by promoting catabolism

c) It inhibits the formation of LDL from IDL

d) It  inhibits the rate limiting step in cholesterol biosynthesis

e) It inhibits synthesis of LDL receptors.

Q.9) -A 35 year-old  woman presents with crushing substernal chest pain and shortness of breath. A coronary artery is occluded due to an atherosclerotic plaque, and she is diagnosed with having myocardial infarction. Her serum cholesterol level is 700 mg/dl. The family history is positive for high cholesterol level and she seems to be having familial hypercholesterolemia. What is the possible biochemical defect in this genetic disorder ?

a) High activity of HMG Co A reductase

b) Low activity of 7-α hydroxylase

c) Abnormal LDL receptors

d) More conversion of VLDL to LDL

e) Less concentration of HDL.

Q.10)- A 40- year-old man  presents with severe pain in the legs upon walking. He is diagnosed with atherosclerotic plaques in the arteries of his legs. High level of cholesterol and LDL contribute to the formation of atherosclerosis. Which of the following is digested to form LDL ?

a) IDL

b) Chylomicrons

c) HDL

d) Cholesteryl esters

e)  Cholesterol.

Q.11- A 23-year-old female presents with  low red blood cell count, corneal opacities and kidney insufficiency. She is diagnosed with lecithin: cholesterol acyl transferase (LCAT) deficiency. In which of the following reactions LCAT is involved ?

a) Transfer of cholesterol esters from HDL to VLDL

b) Hydrolysis of HDL

c) Uptake of cholesterol from liver cells

d) Converting cholesterol to Cholesteryl esters

e) Promoting uptake of HDL in to liver cells

Q.12-  Which of the followings is not a hypolipidemic drug ?

a) Statin

b) Niacin

c) Folic acid

d) Clofibrate

e) Ezetimibe.

Q.13- The synthesis of HMG Co A can take place-

a) only in mitochondria

b) Only in cytoplasm of all  nucleated mammalian cells

c) In the endoplasmic reticulum of all mammalian cells

d) In the lysosomes

e) In both cytosol and mitochondria.

Q.14- Which of the following best describes the role of cholesterol ester transfer protein (CETP) ?

a) It converts cholesterol from LDL to cholesterol esters

b) It is the major protein of HDL

c) It exchanges cholesterol esters from HDL to other lipoproteins

d) It  acts as a ligand for hepatic receptors of HDL

e) It is an activator of LCAT.

Q.15- Which of the followings  are  not  lipotropic agents ?

a) Essential  amino acids

b) Essential fatty acids

c) Vitamin A,C and E

d) Biotin and Pantothenic acid

e) Synthetic antioxidants

 

 

 

Key to Answers-

1)- a,      2)-b,      3)-a,       4)-b,      5)-e,      6)-c,       7)-c,       8)-d,      9)-c,       10)-a,    11)-d,    12)-c

13)-b,    14)-c,     15)-d.

 

Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

Q.1- Glucose can be converted to Glycerol-3-P through which of the following intermediates?

a) Glycerol

b) Dihydroxy acetone phosphate

c) Acetyl co A

d) Pyruvate

e) Malate.

Q.2- Which of the following supplies the 2 carbon units that are added to the elongation of fatty acid chain?

a) Acetyl co A

b) Malonyl co A

c) β- Keto acyl co A

d) Glucose

e) Pyruvate.

Q.3-The conversion of Acetyl co A to Malonyl CoA requires which of the following?

a) Biotin

b) Adenosine Diphosphate (ADP)

c) NADPH

d) H2O

e)  Folic acid.

Q.4- NADPH is synthesized by the action of which of the following enzymes?

a) Glucose-6-P dehydrogenase

b) Pyruvate dehydrogenase

c) Acetyl co A carboxylase

d) Lipoprotein lipase

e) Glycerol kinase.

Q.5- A 45-year-old female presents with severe upper abdominal pain, nausea, and vomiting. She is diagnosed with Pancreatitis (an inflammation of the pancreas).Her serum triglyceride level is found to be 3000 mg/dl and is deemed as the cause for Pancreatitis. To form Triacyl glycerol, which of the following is added to diacyl glycerol?

a) Glycerol

b) Glycerol-3-Phosphate

c) Fatty acyl co A

d) Acetyl co A

e) Succinyl co A.

Q.6- A 35-year-old man presents with yellow xanthomas on his skin and hepatomegaly (enlarged liver). His Triglyceride level is 1500 mg/dl. He is diagnosed with type V hyperlipidemia. Triglycerides are primarily synthesized in which of the following tissues?

a) Skeletal muscle

b) Heart muscle

c) Liver

d) Spleen

e) Blood cells.

Q.7- An 18-year-old female is diagnosed as obese. She maintains a sedentary life style and eats a high-fat, high-sugar diet. Maintenance of this diet and lifestyle has led to lipogenesis and obesity. Which of the following affects excessive fatty acid synthesis?

a) Glycerol is obtained through glycolysis

b) Fatty acids are excessively synthesized from Acetyl co A

c) NADPH is excessively obtained from HMP pathway

d) Triglycerides are excessively synthesized

e) All of the above.

Q.8- A 30- year-old pregnant woman has a sugar craving and consumes a hot fudge sundae. Her serum glucose level increases, which causes release of Insulin. Insulin is known to increase the activity of acetyl co A carboxylase , the rate limiting enzyme of fatty acid biosynthesis. Which of the following best describes this regulatory enzyme?

a) It is activated by carboxylation

b) It catalyzes a reaction that condenses an acetyl group with malonyl group

c) It catalyzes a reaction that requires biotin and ATP

d) It converts Malonyl co A to Acetyl co A

e) It is activated by malonyl co A.

Q.9- A 16-year-old female presents with xanthomas on her eyelids. She is found to have a rare genetic deficiency of lipoprotein lipase and is diagnosed with type 1 hyperlipidemia. In this disorder chylomicrons are abnormally elevated in the serum. In what type of cell are triacylglycerols packaged in to chylomicrons?

a) Intestinal epithelial cells

b) Liver cell

c) Muscle cell

d) Heart cell

e) Adipose cell.

Q.10- A 50-year-old, alcoholic male presents with a swollen face, distended abdomen, and an enlarged fatty liver. Fatty acids react with glycerol-3-P to form triglycerides, which accumulate to cause fatty liver. The liver has glycerol kinase, while adipose tissue lacks glycerol kinase. As a result, in adipose tissue, which of the following occurs?

a) Glucose can not be converted to DHAP

b) Glycerol can not be converted to Glycerol-3-P

c) DHAP can not be converted to Glycerol-3-P

d) Diacylglycerol can not be converted to Triacylglycerol

e) Triacylglycerols can not be stored.

Q.11- A 25-year-old man is brought to the emergency room after a motor vehicle accident. He has a dislocated hip, rib fractures and a facial laceration. Toxicology screen shows a high level of ethanol in his blood. Oxidation of ethanol produces acetaldehyde and NADH. A high level of NADH relative to NAD + slows TCA cycle and promotes the conversion of which of the following reactions?

 a) Dihydroxy acetone phosphate to glycerol-3-P

b) Glycerol-3-P to Dihydroxy acetone phosphate

c) Citrate to isocitrate

d) Malate to Oxalo acetate

e) All of the above.

Q.12- A 35-year-old woman presents with flatulence, bloating, and steatorrhea (fat in the stool). She had been eating large amounts of potato chips that were made using Olestra, a fat substitute. Normally, dietary triacylglycerol are hydrolyzed in to components that are reconstructed into triacylglycerols that become a component of chylomicrons. In the intestinal cell, the initial precursor for fatty acid synthesis is which of the following?

a) Glycerol

b) Glycerol-3-P

c) 2-Mono acyl glycerol

d) Phosphatidic acid

e) Acetyl co A.

Q.13- The complete oxidation of odd chain fatty acid produces which of the followings?

a) Acetyl co A only

b) Acetyl co A and Propionyl co A

c) Butyryl co A

d) Palmitoyl co A

e) Propionyl co A only

Q.14- The activation of long chain fatty acids requires which of the following components?

a) 2 ATP

b) 2 ATP and Co A

c) 2 ATP, Co A and fatty acyl co A

d) Fatty acyl carnitine

e) Carnitine acyl transferase I and II.

Q.15- Which of the following statements best describes the β- oxidation of fatty acids?

a) One Acetyl co A is produced in each turn of the β- oxidation spiral

b) β- oxidation of fatty acids is an extra mitochondrial process

c) The enzymes present in the form of multienzyme complexes

d) The intermediates are carried by Acyl carrier protein

e) 129 ATP are required for the formation of one mol of Palmitic acid.

Q.16- β- oxidation of long chain fatty acids occurs primarily in which of the following locations?

a) Cytosol

b) Peroxisomes

c) Mitochondria

d) Endoplasmic reticulum

e) Golgi apparatus.

Q.17- How many carbons are removed from fatty acyl co A in one turn of β- oxidation spiral ?

a) 1

b) 2

c) 3

d) 4

e) 6

Q.18- β- oxidation of fatty acids is promoted by which of the followings?

a) ATP

b) NAD +

c) FADH2

d) Acetyl co A

e) Propionyl co A.

Q.19- What is the role of Thiolase in the β- oxidation of fatty acids?

a) Cleaves of Co A

b) Cleaves the bond between α- and β- carbons

c) Adds H2O across the double bond

d) Generates NADH

e) Generates FADH2

Q.20- Which of the following products is released in α-oxidation of fatty acids?

a) Co A

b) CO2

c) H2O

d) Acetyl co A

e) Hydrogen peroxide.

Q.21- A 16-year-old extremely slender girl presents with a body weight that is 35% below expected. She still feels herself to be obese and severely restricts her food intake. She is diagnosed with Anorexia Nervosa. In this patient, due to improper dietary intake, the breakdown of fatty acids is required to provide energy. Which of the following substance is formed in the first step of the beta oxidation of fatty acids?

a) ATP

b) Co A

c) Fatty acyl co A

d) Carnitine

e) Malonyl co A.

Q.22- A 5-year-old boy presents with altered mental status, heart failure, and muscle weakness. His serum level of ketones and glucose are abnormally low. He is diagnosed with primary carnitine deficiency. In which of the following is carnitine directly involved?

a) Activation of fatty acids

b) Transport of fatty acyl co A

c) β-Oxidation

d) ω- Oxidation

e) α- Oxidation.

Q.23- A 10-year-old girl presents with difficult walking, muscle weakness and altered mental status. She is diagnosed with carnitine acyl transferase deficiency. Carnitine acyl Transferase-I catalyzes a reaction that produces which of the following?

a) Fatty acyl co A

b) Fatty acyl Carnitine

c) Fatty enoyl co A

d) β- OH- Acyl co A

e) β- Keto acyl co A.

Q.24- An obese, 40-year-old woman, who recently underwent gastric bypass surgery, presents with severe vomiting due to rapid intake of large quantities of food, which must be avoided after gastric bypass surgery. She had successfully lost 10 Ib over the last month after the surgery die to mobilization of fat stores to provide acetyl co A and energy. When palmitoyl co A is oxidised, how many Acetyl co A are produced?

a)1

b) 10

c) 6

d) 8

e) 4

Q.25- A 16-year-old marathon runner trains by running 15 miles every morning, requiring a constant supply of ATP. Approximately How many ATP are produced when palmitoyl co A is oxidized to CO2 and H2O ?

a) 100

b) 129

c) 136

d) 96

e) None of the above.

 

Key to answers- 1)-b,     2)-b,     3)-a,      4)-a,      5) –c,     6)-c,     7)-e,      8)-c,      9)-a,       10)-b,    11)- a,      12)- c,     13)- b,  

                                     14)- b,   15)- a,   16)- c,    17)- b,   18)- b,   19)- b,   20)- b,   21)-c,     22)- b    23)- b,   24)-d,     25)-b.   

Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

1- All except one are true about gastric lipase-

a)   Main preduodenal lipase

b)   Hydrolyzes triglycerides containing short and medium chain fatty acids

c)   Primary site of hydrolysis is sn-3ester linkage

d)   Optimum pH is 6.0-7.0

2- Pancreatic juice does not contain which of the following

a)   Bile salts

b)   Phospholipase A2

c)   Lipase and co lipase

d)   Lipoprotein lipase

3- The dietary fats are transported as –

a)   Micelles

b)   Chylomicrons

c)   Fatty acid – Albumin complex

d)   Liposomes

4-  One and the only energy requiring step in fatty acid oxidation is catalyzed by which of the following enzymes-

a)   Thiolase

b)   Acyl co A dehydrogenase

c)   Thiokinase

d)   Beta-OH Acyl co A dehydrogenase

5- A fatty acid with 14 carbon atoms will undergo how many cycles of beta oxidation

a)   7

b)   4

c)   6

d)   5

6- Which statement best describes the oxidation of odd chain fatty acids?

a)   Additional specific enzymes are needed for the oxidative process

b)   One carbon is removed in one cycle

c)   End product is propionyl co A

d)   Hydroxy fatty acids are produced

7- Which statement out of the following is incorrect about Zellweger syndrome?

a)   Results from the absence of functional peroxisomes

b)   Characterized by hypoglycemia and ketosis

c)   Caused by a defect in the import of enzymes into the peroxisomes

d)   Death occurs within 6 years of life.

8-   What is the molecular basis of the statement “fats burn in the flame of carbohydrates”-?

a)   Fats are hydrolyzed in the presence of carbohydrates

b)   Fatty acids and glucose are simultaneously oxidized

c)   Acetyl co A is the common product of fatty acid and glucose oxidation

d)   Acetyl co A is oxidized completely in the presence of oxaloacetate in TCA cycle

9- Which of the following statements correctly describes the enzyme Thiolase?

a)   It yields Acetoacetyl co A as a product

b)   It yields Malonyl co A as a product

c)   Forms Co A ester as a product

d)   Requires beta keto acyl co A as a substrate

10-NADPH required for the fatty acid synthesis can be generated from-

a)   HMP pathway

b)   Glycolysis

c)   TCA cycle

d)   All of the above

11- Which of the following is not used for fatty acid synthesis?

a)   Cobalamine

b)   NADPH

c)   Biotin

d)   Bicarbonate

12-The key regulatory enzyme of fatty acid synthesis is-

a)   Acyl co A synthetase

b)   Acetyl co A carboxylase

c)   Keto acyl synthase

d)   Thioesterase

13- Malonyl-CoA A is a direct inhibitor of which enzyme of fatty acid oxidation?

a)   Carnitine Acyl Transferase –I

b)   Carnitine Acyl Transferase –II

c)   Thiokinase

d)   None of the above

14- When the liver is actively synthesizing fatty acids, a concomitant decrease in beta oxidation of fatty acids is due to

a)   Inhibition by end product

b)   Decrease in adipolysis

c)    Inactivation of specific enzymes of fatty acid oxidation

d)   Inhibition of translocation between cellular compartments

15-  Which out of the following is the primary ketone body?

a)   Acetone

b)   Acetoacetate

c)   Beta-hydroxy butyrate

d)   Hydroxy Methyl glutarate

16-  All are conditions of ketosis except one –

a)   Starvation

b)   Uncontrolled diabetes mellitus

c)   High carbohydrate  diet

d)   Von Gierke’s disease

17-The key enzyme for the utilization of ketone bodies is-

a)   Thiolase

b)   Thiophorase

c)   Thiokinase

d)   Thioesterase

18-The key regulatory enzyme of cholesterol synthesis is-

a)   HMG- Co A synthase

b)   HMG Co A lyase

c)   HMG Co A reductase

d)   Mevalonate kinase

19- Choose the incorrect statement about cholesterol synthesis

a)   All the carbon atoms are derived from Acetyl CoA

b)   Process is cytoplasmic

c)   NADPH is the main coenzyme

d)   Highly expensive energetically

20- The process by which bile acid sequestrants lower serum cholesterol level is-

a)   Direct Inhibition of cholesterol synthesis

b)   Promote cholesterol catabolism

c)   Promote cholesterol excretion

d)   Divert cholesterol metabolism towards bile acid formation

Key to answers-

1) – d

2) – d

3) -b

4)- c

5)- c

6)- c

7)- c

8)- d

9)-d

10)- a

11)-a

12)-b

13)- a

14)-d

15)-b

16)- c

17)- b

18)- c

19)-b

20)-d


Please help "Biochemistry for Medics" by CLICKING ON THE ADVERTISEMENTS above!

Advertisement