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1- What is the expected clinical outcome of niacin deficiency ?

Answer- Niacin deficiency in severe form is manifested as Pellagra. Disoriented memory (dementia), diarrhea and dermatitis are the signs of pellagra. In untreated cases it leads to death (4 Ds)

2- Why should milk be preferably stored in dark bottles?

Answer- Riboflavin (B1) present in milk is photosensitive, it is destroyed upon exposure to light. Hence to avoid, milk should be stored in dark bottles.

3- Why are premature infants given vitamin K injections immediately after birth?

Answer- Newborn infants, in general, have low vitamin K status for the following reasons:

a) Vitamin K is not easily transported across the placental barrier;

b) The newborn’s intestines are not yet colonized with bacteria that synthesize menaquinones; and

c) The vitamin K cycle may not be fully functional in newborns, especially premature infants.

4- The patients suffering from Carcinoid syndrome generally manifest pellagra like rashes, what could be the reason for this?

Answer- In carcinoid syndrome, tryptophan metabolism is diverted towards serotonin production and less is available for the synthesis of niacin. Niacin deficiency is thus manifested as dementia, dermatitis and diarrhea (pellagra).

5- Which vitamin deficiency is associated with Methyl malonic aciduria?

Answer- Vitamin B12 deficiency is required as a coenzyme for the activity of methyl malonyl co A mutase enzyme that catalyzes the conversion of L-Methyl malonyl co A to Succinyl co A. In vitamin B12 deficiency this conversion is impaired with the resultant excessive accumulation of methyl malonic acid in serum as well as excretion in urine.

6- Which Carboxylation reaction does not require Biotin for its activity?

Answer- Generally biotin is required as a coenzyme for the carboxylation reactions , but gamma carboxylation of specific glutamic acid residues in certain proteins is vitamin K dependent, as in factor II, VII, IX and X of coagulation cascade and osteocalcein (calcium binding proteins).

7- Name two TPP dependent enzymes.

Answer- TPP (Thiamine pyro phosphate), the active form of thiamine is required as a coenzyme for enzymes such as Pyruvate dehydrogenase, Alpha-ketoglutarate dehydrogenase, and branched chain keto acids (BCKA) dehydrogenase complexes and Transketolase.

8- Which vitamin deficiency is associated with Sideroblastic anemia?

Answer- Vitamin B6 deficiency is associated with sideroblastic anemia as it is required as a coenzyme in the pathway of heme biosynthesis (for ALA synthase enzyme).Deficiency leads to impaired heme synthesis and thus reduced Hb synthesis. Deranged heme synthesis in the developing red cell leads to decreased hemoglobin production with the formation of hypochromic and microcytic red cells and other misshaped erythrocytes. These red cells are the progeny of the ring sideroblasts that constitute the diagnostic hallmark of any sideroblastic anemia. 

9 – Which vitamin is known to participate in Carnitine synthesis?

Answer- Vitamin C is required for the synthesis of carnitine. Carnitine is required for the transportation of fatty acid across the inner mitochondrial membrane in to the mitochondrial matrix where the oxidation of fatty acids takes place.

10 – Name the antioxidant vitamins.

Answer-An antioxidant is a substance that significantly decreases the harmful effects of “reactive species”, such as reactive oxygen and nitrogen molecules that disrupt normal physiological function on a cellular level in humans. Examples include the antioxidant vitamin C, vitamin E, and the carotenoids (vitamin A). Selenium is also an antioxidant.  A multitude of other nutrients, including minerals such as copper, manganese, and zinc, flavonoids, and coenzyme Q10, also possess antioxidant properties.

11- What are the clinical findings in a case of Rickets?

Answer- Rickets is caused by a failure of osteoid to calcify in growing children. It occurs due to vitamin D deficiency.  The clinical manifestations include-frontal bossing,bow legs, knock-knees, rachitic rosary along the costochondral junctions, Harrison groove and in more severe instances in children older than 2 years, vertebral softening leading to Kyphoscoliosis. In the long bones, laying down of uncalcified osteoid at the metaphysis leads to spreading of those areas, producing knobby deformity.

12- What are the target organs /tissues for the action of vitamin D ?

Answer- The target organs for vitamin D are bone, intestine and kidney. The basic function of vitamin D is to promote the reabsorption of calcium so as to maintain the serum calcium levels and to promote the mineralization of bones.

13- Which vitamin is known to participate in the oxidative deamination reactions of amino acids?

Answer- Riboflavin is required for the oxidative deamination reactions. FMN form is required for L-amino acid oxidases while FAD is required for D-amino acid oxidases.

14- Which water soluble vitamin is stored in liver ?

Answer- Vitamin B12 is the only water soluble vitamin that is stored in the body (in the liver). The liver contains 2000–5000 mcg of stored vitamin B12. Since daily losses are 3–5 mcg/d, the body usually has sufficient stores of vitamin B12 so that vitamin B12 deficiency develops more than 3 years after vitamin B12 absorption ceases.

15- Why is vitamin D considered a hormone?

Answer- Vitamin D is actually a hormone since its mechanism of action resembles that of hormones. Like hormones it is required only in small amount. Most if not all actions of vitamin D are mediated through a nuclear transcription factor known as the vitamin D receptor (VDR) similar to hormones.


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