Q-1. Which of the following is a water soluble vitamin?
a) Folic acid
b) Vitamin A
c) Vitamin K
d) Linolenic acid
Answer: Folic acid
Explanation:
Fat soluble vitamins:
Vitamin A
Vitamin D
Vitamin E
Vitamin K
Water soluble vitamins:
B-complex
Vitamin C
Q-2. Vitamin which prevent oxidation
a) Pyridoxine
b) Biotin
c) Vit A
d) Thiamine
Answer: Vit A
Explanation:
Antioxidant vitamins are:
Vitamin A
Vitamin C
Vitamin E
Other antioxidant nutrients:
Selenium
Polyphenolic compound
Q-3. Which of the following combinations of biologically active molecules does vitamin A consists of? (AIIMS May 2004)
a) Retinol, retinal and retinoic acid
b) Retinol, retinal and tetra-hydro-folate
c) Retinal, conjugase and retinoic acid
d) PABA, retinol and retinal-aldehyde
Answer: Retinol, retinal and retinoic acid
Explanation:
Biologically active forms of Vitamin A:
Retinol
Retinal
Retinoic acid
Beta carotene
Q-4. Which of the following is a component of the visual pigment Rhodopsin? (AIIMS Nov 205)
a) b-carotene
b) Retinal
c) Retinol
d) Retinoic acid
Answer: Retinal
Explanation:
In retina, retinaldehyde functions as prosthetic group of the light sensitive opsin proteins, forming Rhodopsin in rods and Idopsin in cones.
All trans retinoic acid and 9-cis retinoic acid regulate growth, development and tissue differentiation.
Important points:
Beta carotene and other pro-vitamin-A carotenoids are cleaved in intestinal mucosa by carotene di-oxidase, yielding retinaldehyde which reduced to retinol, esterified and secreted in chylomicrons.
Retinol esters contained in chylomicrons are taken up by and stored in the liver.
Q-5. Vitamin A is stored mainly as retinol esters in: (AIIMS Nov 205)
a) Kidney
b) Muscle
c) Liver
d) Retina
Answer: Liver
Explanation:
See above explanation.
Q-6. Initiation of visual impulse is associated with
a) Condensation of opsin with vitamin-A aldehyde
b) Photo-isomerization and hydrolysis of visual purple
c) Decreased NADP
d) Decreased NAD
Answer: Photo-isomerization and hydrolysis of visual purple
Explanation:
Absorption of light by Rhodopsin (11 Cis Retinal + opsin)> Isomerization of retinaldehyde from 11 Cis to All Trans> Conformational change in opsin> Hydrolysis of Rhodopsin (Visual purple) to release All Trans retinaldehyde and opsin
Q-7. Vitamin A intoxication causes injury to: (AIIMS May 2007)
a) Cytosol
b) Mitochondria
c) Lysosomes
d) Cell membrane
Answer: Lysosomes
Explanation:
Vitamin A intoxication causes rupture of lysosomal membrane.
Hyper-vitaminosis A:
Headache, nausea, ataxia and anorexia all associated with increased cerebrospinal fluid pressure
Hepatomegaly and hyperlipidemia
Calcification of soft tissue, thickening of long bone and hyper-calcemia
Dry skin, desquamation and alopecia
Q-8. Active form of vitamin D is (AIIMS May 2007)
a) Ergocalciferol
b) Cholecalciferol
c) 25-hydroxycholecalciferol
d) 1, 25-dihydroxycholecalciferol
Answer: 1, 25-dihydroxycholecalciferol
Explanation:
Ergocalciferol or Vitamin D2: Found in plants
Cholecalciferol or Vitamin D3: Found in animals
25-hydroxycholecalciferol: Prominent form of Vitamin D in the plasma and major storage form of the vitamin
1, 25-dihydroxycholecalciferol: Biological active form of Vitamin D
Q-9. Which fat soluble vitamin is functioning like a Hormone?
a) Vit A
b) Vit D
c) Vit E
d) Vit K
Answer: Vit D
Explanation:
Vitamin D is not strictly a vitamin, since it can be synthesized in the skin and under most conditions that is major source of vitamin.
Most of Vitamin D actions are mediated by way of nuclear receptors that regulate gene expression.
Its main function is the regulation of calcium absorption and homeostasis. It also has role in regulating cell proliferation and differentiation.
Important point:
Higher dose reduces risk of insulin resistance, obesity, metabolic syndrome and various cancers.
Q-10. Hemolytic anemia of new born is due to deficiency of Vitamin
a) A
b) D
c) E
d) K
Answer: Vitamin E
Explanation:
Hemolytic anemia of new born:
Premature infants are born with inadequate reserves of vitamin E. The erythrocyte membranes are abnormally fragile as result of per-oxidation, lead to hemolytic anemia.
Important point:
The main function of vitamin E is as a chain breaking, free radical trapping antioxidant in cell membranes and plasma lipo-proteins by reacting with the lipid peroxide radicals formed by per-oxidation of poly-unsaturated fatty acids.
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Q-11. Vitamin K is required for: (AIIMS Nov 2007)
a) Carboxylation
b) Hydroxylation
c) Chelation
d) Transamination
Answer: Carboxylation
Explanation:
Gamma-glutamyl carboxylase is an enzyme that catalyzes the posttranslational modification of vitamin K-dependent proteins.
Vitamin K is involved in the carboxylation of certain glutamate residues in proteins to form gamma-carboxy-glutamate (Gla) residues.
Prothrombin, Factors VII, IX, X and protein C and S (Vit-K dependent clotting factors) each contain 4-6 gamma carboxy-glutamate residues. Gamma carboxy-glutamate chelates calcium ions and so permits the binding of the blood clotting proteins to membranes.
Important points:
Two proteins that contain gamma carboxy-glutamate are present in bone, osteocalcin and bone matrix Gla protein. Osteocalcin also contains hydroxy-proline, so its synthesis is dependent on both vitamin K and C; in addition, its synthesis is induced by Vitamin D.
Q-12. In carboxylation of clotting factors by Vitamin K, which of the following amino acid is carboxylated? (AIIMS Nov 2008)
a) Aspartate
b) Glutamate
c) Histamine
d) Histidine
Answer: Glutamate
Explanation:
See above explanation.
Q-13. Vitamin K is needed for which of these post translational modification processes: (AIIMS May 2001)
a) Methylation
b) Carboxylation
c) Hydroxylation
d) Transketolation
Answer: Carboxylation
Explanation:
See above explanation.
Q-14. Both Vitamin K and C are involved in:
a) The synthesis of clotting factors
b) Post translational modifications
c) Antioxidant mechanisms
d) The microsomal hydroxylation reactions
Answer: Post translational modifications
Explanation:
See above explanation.
Important point:
The posttranslational modifications of proteins that depend upon vitamin C as a cofactor include proline and lysine hydroxylations and carboxy terminal amidation. The hydroxylating enzymes are identified as prolyl hydroxylase and lysyl hydroxylase. The donor of the amide for C-terminal amidation is glycine. The most important hydroxylated proteins are the collagens. Several peptide hormones such as oxytocin and vasopressin have C-terminal amidation.
Q-15. Which Vitamin is required for carboxylation clotting factors?
a) Vitamin A
b) Vitamin D
c) Vitamin E
d) Vitamin K
Answer: Vitamin K
Explanation:
See above explanation.
Q-16. Vitamin K is involved in the post translational modification of?
a) Glutamate
b) Aspartate
c) Tyrosine
d) Tryptophan
Answer: Glutamate
Explanation:
See above explanation.
Q-17. Thiamine deficiency causes decreased energy production because?
a) It is required for the process of transamination
b) It is co-factor in oxidative reduction
c) It is co-enzyme for trans-ketolase in pentose phosphate pathway
d) It is co-enzyme for pyruvate dehydrogenase & alpha ketoglutarate dehydrogenase
Answer: It is co-enzyme for pyruvate dehydrogenase & alpha ketoglutarate dehydrogenase
Explanation:
Thiamine has a central role in energy yielding metabolism, and especially the metabolism of carbohydrates.
Thiamine diphosphate is the coenzyme for three multi-enzyme complexes that catalyze oxidative decarboxylation reactions:
Pyruvate dehydrogenase in carbohydrate metabolism
Alpha keto-glutarate dehydrogenase in Citric Acid Cycle
Branched chain keto-acid dehydrogenase involved in the metabolism of leucine, iso-leucine and valine
Important points:
Thiamine diphosphate is also the coenzyme for trans-ketolase on PPP.
Thiamine trisphosphate has a role in nerve conduction; it phosphorylates, and so activates a chloride channel in the nerve membrane.
Q-18. Thiamine requirement increases in excessive intake of: (AIIMS May 2009)
a) Carbohydrates
b) Fats
c) Proteins
d) None
Answer: Carbohydrates
Explanation:
See Above explanation.
Important points:
The enzymes trans-ketolase, pyruvate dehydrogenase (PDH), and α-keto-glutarate dehydrogenase are all important in carbohydrate metabolism.
The cytosolic enzyme trans-ketolase is a key player in the pentose phosphate pathway, a major route for the biosynthesis of the pentose sugars deoxyribose and ribose.
The mitochondrial Pyruvate dehydrogenase and α-keto-glutarate dehydrogenase are part of biochemical pathways that result in the generation of adenosine tri-phosphate (ATP), which is a major form of energy for the cell.
Q-19. Which of the following statement about thiamine is true? (AIIMS Nov 2008)
a) It is required for the process of Transamination
b) It is co-enzyme for lactate dehydrogenase
c) Its co-enzyme function is done by thiamine mono-phosphate
d) It is co-enzyme for private dehydrogenase and alfa keto-glutarate dehydrogenase
Answer: It is co-enzyme for private dehydrogenase and alfa keto-glutarate dehydrogenase
Explanation:
See Above explanation.
Q-20. Thiamine deficiency causes decreased energy production because: (AIIMS May 2008)
a) It is required for the process of Transamination
b) It is co-enzyme for trans-ketolase in pentose phosphate pathway
c) It is co-enzyme in oxidative reduction
d) It is co-enzyme for private dehydrogenase
Answer: It is co-enzyme for private dehydrogenase
Explanation:
See Above explanation.
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Q-21. Thiamine is not used in which of the following reactions? (AIIMS May 2001)
a) Glucose to pentose
b) Lactate to Pyruvate
c) Oxidative decarboxylation of Alfa-keto amino acids
d) Alfa-keto glutarate to succinyl Co-A
Answer: Lactate to Pyruvate
Explanation:
See Above explanation.
Lactate dehydrogenase catalyzes the inter-conversion of pyruvate and lactate with concomitant inter-conversion of NADH and NAD+. Co-enzyme is niacin.
Q-22. Which of the vitamin deficiency lead to lactic acidosis? (AIIMS Nov 2010)
a) Riboflavin
b) Thiamin
c) Niacin
d) Panthothenic acid
Answer: Thiamin
Explanation:
See Above explanation.
Important points:
The roll of thiamine di-phosphate in pyruvate dehydrogenase means that in deficiency there is impaired conversion of pyruvate to acetyl Co-A.
In subjects on a relatively high carbohydrate diet, this result in increased plasma concentration of lactate and pyruvate, this may cause life threatening lactic acidosis.
Q-23. Thiamin level is best monitored by best monitored by
a) Trans-ketolase level in blood
b) Thiamine level in blood
c) G-6-PD activity
d) Reticulocytosis
Answer: Trans-ketolase level in blood
Explanation:
The role of thiamin diphosphate in pyruvate dehydrogenase means that in deficiency there is impaired conversion of pyruvate to acetyl Co-A resulting in increased plasma concentration of lactate and pyruvate which may cause life threatening lactic acidosis.
Thiamin nutritional status can be assessed by erythrocyte trans-ketolase activation.
Important point: Thiamin deficiency:
Chronic peripheral neuritis
Beriberi with or without heart failure and edema
Wernicke encephalopathy with Korsakoff psychosis associated specially with alcohol and narcosis
Lactic acidosis in subjects on a relatively high carbohydrate diet
Q-24. Which vitamin in large doses decreases triglyceride and cholesterol?
a) Vit B1
b) Nicotinic acid
c) Vit B12
d) Riboflavin
Answer: Nicotinic acid
Explanation
Nicotinic acid reduces the production of triglycerides and VLDL.
This leads to decreased LDL cholesterol, increased HDL cholesterol, and lowered triglycerides.
Q-25. A middle aged woman on oral contraceptives for many years developed neurological symptoms such as depression, irritability, nervousness and mental confusion. Her hemoglobin level was 8 g/dl. Biochemical investigations revealed that she was excreting highly elevated concentrations of xanthurenic acid in urine. She also showed high levels of triglycerides and cholesterol in serum.
All of the above findings are most probably related to Vitamin B6 deficiency caused by prolonged oral contraceptive use except:
a) Increased urinary Xanthurenic acid excretion
b) Neurological symptoms by decreased synthesis of biogenic amines
c) Decreased hemoglobin level
d) Increased triglyceride and cholesterol level
Answer: Increased triglyceride and cholesterol level
Explanation:
Pyridoxal phosphate is a coenzyme for many enzymes involved in amino acid metabolism, especially transamination and decarboxylation.
It is also the cofactor of glycogen phosphorylase, where the phosphate group is catalytically important.
Pyridoxine deficiency has been observed in:
Patients taking isoniazid
New born infants fed formulas low in Vitamin B6
Women taking oral contraceptives
Alcoholics
Important point:
Isoniazid can induce a B6 deficiency by forming an inactive derivative with Pyridoxal phosphate.
Q-26. Vitamin B12 acts as co-enzyme to which one of the following enzymes?
a) Iso-citrate dehydrogenase
b) Homocysteine methyl transferase
c) Glycogen synthase
d) G-6-P dehydrogenase
Answer: Homocysteine methyl transferase
Explanation:
Methyl-malonyl Co-A mutase, leucine amino-mutase, methionine synthase and homocysteine methyl transferase are Vitamin B12 dependent enzyme.
Q-27. Vitamin B12 and folic acid supplementation in megaloblastic anemia leads to the improvement of anemia due to
a) Increased DNA synthesis in bone marrow
b) Increased hemoglobin production
c) Erythroid hyperplasia
d) Increased iron absorption
Answer: Increased DNA synthesis in bone marrow
Explanation:
Impairment of methionine synthase in B12 deficiency results in the accumulation of methyl tetra-hydro-folate- folate trap.
There is therefore functional deficiency of folate secondary to the deficiency of Vitamin B12.
Deficiency of folic acid itself or deficiency of Vitamin B12, which leads to functional deficiency of folate, affects cells that are dividing rapidly because they have a large requirement for thymidine for DNA synthesis.
Clinically, this affects the bone marrow leading to megaloblastic anemia.
Important points:
The most common cause of pernicious anemia is failure of absorption of Vitamin B12 rather than dietary deficiency.
This can be result of failure of intrinsic factor secretion caused by chronic use of proton pump inhibitors and autoimmune disease affecting parietal cells or from the production of anti-intrinsic factor antibodies.
Q-28. A baby presents with refusal to feed, skin lesions, seizures, ketosis, organic acids in urine with normal ammonia; likely diagnosis is
a) Propionic aciduria
b) Multiple carboxylase deficiency
c) Maple syrup urine disease
d) Urea cycle enzyme deficiency
Answer: Multiple carboxylase deficiency
Explanation:
Biotin is a coenzyme for pyruvate carboxylase, propionyl-CoA carboxylase, beta-methylcrotonyl-CoA carboxylase, and acetyl-CoA carboxylase.
Multiple carboxylase deficiency is one of many metabolic disorders that occur in the absence of the coenzyme activity of biotin.
Presentation of multiple carboxylase deficiency:
Intractable seizures, hypotonia, spastic para-paresis, unexplained visual loss or visual field loss, unexplained sensorineural hearing loss
Achromotrichia), alopecia, and an eczematous, scaly peri-oral and facial rashes
Metabolic keto-acidosis or organic acidosis
Immunologic dysfunction
Failure to thrive
Important point:
Normal levels of ammonia rule out urea cycle enzyme deficiency.
Q-29. Treatment of multiple carboxylase deficiency is
a) Biotin
b) Pyridoxine
c) Thiamine
d) Folic acid
Answer: Biotin
Explanation:
See above explanation.
Treatment of multiple carboxylase deficiency is administration of biotin.
Q-30. Vitamin needed for Acetyl Co-A carboxylase is
a) Thiamine
b) Riboflavin
c) Niacin
d) Biotin
Answer: Biotin
Explanation
See above explanation.
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Q-31. The activity of following enzyme is affected by biotin deficiency (AIIMS May 2003)
a) Trans-ketolase
b) Oxidase
c) Carboxylase
d) Dehydrogenase
Answer: Carboxylase
Explanation:
See above explanation.
Q-32. Which co-enzyme is responsible for carboxylation reaction? (AIIMS Nov 2008)
A) Biotin
b) FAD
c) NADH
d) Thiamine pyrophosphate
Answer: Biotin
Explanation:
See above explanation.
Q-33. Vitamin excreted in urine: (AIIMS May 2007)
a) Vitamin A
b) Vitamin D
c) Vitamin C
d) Vitamin E
Answer: Vitamin C
Explanation:
Vitamin A, D, K and E are fat soluble vitamins. They are not readily excreted in the urine and significant quantities are stored in the liver and adipose tissue.
In contrast to water soluble vitamins are Vitamin C and B
Q-34. Which of the following is a non-essential metal/mineral? (AIIMS Nov 2010)
a) Sodium
b) Manganese
c) Iron
d) Lead
Answer: Lead
Explanation:
Major minerals: Sodium, Potassium, Chloride, Calcium, Phosphorus, Magnesium and Sulfur
Trace minerals (micro-minerals): Iron, Zinc, Iodine, Selenium, Copper, Manganese, Chromium, F- and Mo.
Q-35. Which of the following is considered the active form of calcium?
a) Ionized calcium
b) Albumin bound calcium
c) Phosphate bound calcium
d) Protein bound calcium
Answer: Ionized calcium
Explanation:
About 50 % total calcium is ionized and ionized calcium is physiologically active form of calcium.
Remaining 50 % of total calcium is bound, mainly to albumin.
Q-36. In which of the following reactions is magnesium required?
a) ATPase
b) Dismutase
c) Phosphatase
d) Aldolase
Answer: Phosphatase
Explanation:
Mg++ is required in:
Phosphatase
Kinase
Ribonuclease
Peptidase
Ca carboxylase
Adenyl cyclase
Trans-ketolase