Vitamins, minerals and nutrition

34 Kerala MSc MLT Entrance practice questions on Vitamins, minerals and nutrition, part of Biochemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   For which nutrient is the specific dynamic action (thermic effect) of food greatest?

   1. AFat
   2. BCarbohydrate
   3. CProtein
   4. DA mixed diet

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   Answer: C · Protein

   Specific dynamic action is the extra heat produced in processing food after a meal. It is about 30% of the energy of protein, compared with about 5% for carbohydrate and a similarly low figure for fat (texts quote about 4-13%). Much of it comes from deamination and urea synthesis. A mixed diet has an overall SDA of about 10%, which is added when calculating energy needs.

   • A: Fat has a much lower SDA than protein.
   • B: Carbohydrate has an SDA of only about 5%.
   • D: A mixed diet averages about 10%, less than protein.

2. Question 2 · Easy

   Vitamin K is needed for which modification of prothrombin and factors VII, IX and X?

   1. AGlycosylation of asparagine residues
   2. BPhosphorylation of serine residues
   3. CHydroxylation of proline residues
   4. DGamma-carboxylation of glutamate residues

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   Answer: D · Gamma-carboxylation of glutamate residues

   Vitamin K hydroquinone is the cofactor for gamma-glutamyl carboxylase in the liver. The extra carboxyl groups let these factors bind calcium and attach to phospholipid surfaces. Warfarin blocks vitamin K epoxide reductase, so non-carboxylated factors (PIVKAs) are released. Proteins C and S and osteocalcin also need this step.

   • A: Asparagine glycosylation does not depend on vitamin K.
   • B: Serine phosphorylation is done by kinases, not vitamin K.
   • C: Proline hydroxylation needs vitamin C and occurs in collagen.

3. Question 3 · Medium

   In vitamin B12 deficiency, serum folate is often normal or even high. The reason is that:

   1. AIntrinsic factor also carries folate into cells
   2. BFolate is trapped as 5-methyltetrahydrofolate
   3. CDamaged red cells release their folate
   4. DB12 deficiency increases folate absorption

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   Answer: B · Folate is trapped as 5-methyltetrahydrofolate

   Methionine synthase needs methylcobalamin to remove the methyl group from 5-methyltetrahydrofolate. Without B12 this step stops, and folate accumulates in plasma as 5-methyl-THF, which cells cannot retain or use. Cells therefore lack usable folate for DNA synthesis even though serum folate looks normal. This 'methyl-folate trap' explains why B12 deficiency causes the same megaloblastic picture as folate deficiency.

   • A: Intrinsic factor binds B12 only.
   • C: Red cell folate falls in B12 deficiency; it is not released to raise serum folate.
   • D: B12 deficiency does not increase folate absorption.

4. Question 4 · Medium

   In the Fiske-Subbarow method, in what form is serum inorganic phosphate measured?

   1. AMolybdenum blue from reduced phosphomolybdate
   2. BA red complex with o-cresolphthalein complexone
   3. CUnreduced phosphomolybdate read at 340 nm
   4. DA purple complex with calmagite

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   Answer: A · Molybdenum blue from reduced phosphomolybdate

   A protein-free filtrate is treated with acid ammonium molybdate, forming phosphomolybdic acid. 1-amino-2-naphthol-4-sulphonic acid then reduces it to molybdenum blue, read colorimetrically. Haemolysis or delayed separation falsely raises phosphate, as red cells contain organic phosphates that are hydrolysed. Most analysers now read unreduced phosphomolybdate at 340 nm instead.

   • B: o-Cresolphthalein complexone measures calcium.
   • C: Reading unreduced phosphomolybdate at 340 nm is a different, modern method.
   • D: Calmagite measures magnesium.

5. Question 5 · Medium

   Vitamin C increases the absorption of dietary non-haem iron mainly because it:

   1. ABuilds the iron into haem in the gut
   2. BIncreases the synthesis of transferrin
   3. CReduces ferric iron to the ferrous form
   4. DRaises the release of hepcidin from the liver

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   Answer: C · Reduces ferric iron to the ferrous form

   Non-haem iron in food is mostly ferric (Fe3+), which forms insoluble complexes at intestinal pH. Ascorbic acid reduces it to ferrous iron (Fe2+) and keeps it soluble, so the divalent metal transporter 1 can take it up in the duodenum. This is why iron tablets are often advised with citrus fruit. Phytates and tannins in tea have the opposite effect.

   • A: The gut does not make haem from dietary iron for absorption.
   • B: Transferrin synthesis follows body iron stores, not vitamin C.
   • D: Hepcidin reduces iron absorption, so raising it would lower uptake.

6. Question 6 · Hard

   A 15-year-old has tremor and a raised ALT. Results: ceruloplasmin 7 mg/dL (reference 20-40), total serum copper 40 µg/dL (reference 70-140), 24-hour urine copper 260 µg (reference below 40). Why is serum copper low while urine copper is high?

   1. AFree copper is raised while bound copper is low
   2. BCopper moves into red cells after collection
   3. CDamaged tubules leak ceruloplasmin into urine
   4. DAbsorption of dietary copper is reduced

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7. Question 7 · Hard

   A 3-year-old girl has bowed legs, as her father did as a child. Results: calcium 9.4 mg/dL (reference 8.5-10.5), phosphorus 2.1 mg/dL (reference for age 4.0-6.5), ALP high for age, PTH normal, 25-hydroxyvitamin D normal, and low tubular reabsorption of phosphate. The most likely diagnosis is:

   1. A1-alpha-hydroxylase deficiency
   2. BX-linked hypophosphataemic rickets
   3. CHypoparathyroidism
   4. DNutritional vitamin D deficiency rickets

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8. Question 8 · Medium

   In beriberi, blood pyruvate and lactate rise mainly because thiamine pyrophosphate is the coenzyme for:

   1. APyruvate dehydrogenase
   2. BPyruvate kinase
   3. CLactate dehydrogenase (LDH)
   4. DPyruvate carboxylase

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9. Question 9 · Easy

   Eating large amounts of raw egg white can cause deficiency of which vitamin, because avidin binds it?

   1. APyridoxine
   2. BRiboflavin
   3. CBiotin
   4. DPantothenic acid

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10. Question 10 · Hard

    A 58-year-old man with flushing and diarrhoea has liver metastases from a small-bowel carcinoid, and his urine 5-HIAA is greatly raised. He develops a rough, scaly rash on sun-exposed skin. The rash is best explained by:

    1. APyridoxine loss in serotonin synthesis
    2. BNiacin deficiency from diverted tryptophan
    3. CZinc deficiency from chronic diarrhoea
    4. DRiboflavin deficiency from poor intake

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11. Question 11 · Medium

    Serum methylmalonic acid is raised in vitamin B12 deficiency but not in folate deficiency. The reason is that adenosylcobalamin is the coenzyme for:

    1. AMethionine synthase
    2. BMethylmalonyl-CoA mutase
    3. CPropionyl-CoA carboxylase
    4. DThymidylate synthase

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12. Question 12 · Medium

    Poor wound healing and fragile capillaries in scurvy result mainly from failure of which reaction?

    1. ACarboxylation of glutamate residues in collagen
    2. BCross-linking of collagen fibres by lysyl oxidase
    3. CHydroxylation of proline and lysine in procollagen
    4. DGlycosylation of hydroxylysine in procollagen

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13. Question 13 · Medium

    After an oral histidine load, a marked rise in urinary formiminoglutamic acid (FIGLU) points to deficiency of:

    1. APyridoxine
    2. BBiotin
    3. CNiacin
    4. DFolic acid

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14. Question 14 · Easy

    Intrinsic factor, the glycoprotein needed for vitamin B12 absorption in the terminal ileum, is secreted by the:

    1. AParietal cells of the stomach
    2. BAcinar cells of the pancreas
    3. CChief cells of the stomach
    4. DEnterocytes of the terminal ileum

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15. Question 15 · Easy

    Foamy, greyish triangular patches on the bulbar conjunctiva (Bitot's spots) in a young child point to deficiency of:

    1. AVitamin C
    2. BVitamin E
    3. CVitamin A
    4. DRiboflavin

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16. Question 16 · Hard

    A 34-year-old man weighs 78 kg and is 1.70 m tall. Using the Indian consensus cut-offs for adults (normal 18.0-22.9, overweight 23.0-24.9, obese 25.0 kg/m2 or more), he is classed as:

    1. AUnderweight
    2. BObese
    3. COverweight
    4. DNormal weight

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17. Question 17 · Hard

    A 58-year-old on omeprazole for 4 years and a thiazide has tetany. Results: calcium 7.0 mg/dL (reference 8.5-10.5), albumin 4.2 g/dL, phosphate 3.8 mg/dL (2.5-4.5), PTH 12 pg/mL (15-65), magnesium 0.7 mg/dL (1.7-2.4). Intravenous calcium gives only brief relief. The most appropriate next step is to:

    1. AGive a phosphate binder
    2. BCorrect the magnesium deficit
    3. CStart oral calcitriol
    4. DIncrease the calcium infusion rate

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18. Question 18 · Medium

    A premature infant fed a formula rich in polyunsaturated fat but low in vitamin E develops haemolytic anaemia. Vitamin E protects the red cell mainly by:

    1. AKeeping glutathione in the reduced state
    2. BBreaking lipid peroxidation chains in the membrane
    3. CStabilising spectrin in the membrane skeleton
    4. DActing as coenzyme for glucose-6-phosphate dehydrogenase

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19. Question 19 · Easy

    Keshan disease, an endemic cardiomyopathy of children, is linked to dietary deficiency of which trace element?

    1. ACopper
    2. BChromium
    3. CSelenium
    4. DZinc

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20. Question 20 · Medium

    A student hyperventilating during an anxiety attack develops carpopedal spasm, although total serum calcium is normal. The spasm occurs because the alkalosis:

    1. AIncreases calcium binding to albumin and lowers ionised calcium
    2. BShifts calcium from plasma into the bone matrix
    3. CIncreases the loss of calcium into the urine
    4. DSuppresses the secretion of parathyroid hormone

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21. Question 21 · Hard

    A 60-year-old woman who eats meat daily has megaloblastic anaemia with numb feet. Serum B12 is 95 pg/mL (reference 200-900), folate is normal and endoscopy shows atrophic gastritis of the body of the stomach. Which test best confirms the cause of her B12 deficiency?

    1. ASerum methylmalonic acid
    2. BSerum total homocysteine
    3. CRed cell folate
    4. DAnti-intrinsic factor antibody

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22. Question 22 · Medium

    In anaemia of chronic disease, serum iron is low despite ample stores because inflammation raises hepcidin, which:

    1. ADegrades ferroportin and traps iron inside macrophages
    2. BBlocks transferrin receptors on developing erythroblasts
    3. CBinds circulating iron and carries it to the liver
    4. DIncreases the excretion of iron by the kidneys

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23. Question 23 · Hard

    A 9-month-old fed only on goat's milk since weaning is pale and irritable. Results: Hb 7.8 g/dL, MCV 112 fL, hypersegmented neutrophils, serum B12 420 pg/mL (reference 200-900), serum folate 1.8 ng/mL (reference 3-17), ferritin 40 ng/mL (reference 12-150). The most likely cause of the anaemia is:

    1. AIron deficiency from a milk-only diet
    2. BAnaemia of chronic inflammation
    3. CDietary folate deficiency
    4. DDietary vitamin B12 deficiency

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24. Question 24 · Medium

    Pellagra occurs in people whose staple cereal is jowar (sorghum), even though its niacin content is adequate. The explanation given in Indian texts is that jowar:

    1. AHolds its niacin as bound niacytin, which is not absorbed
    2. BHas excess leucine, which hinders niacin synthesis from tryptophan
    3. CContains an antivitamin that destroys nicotinamide in the gut
    4. DHas no tryptophan at all from which NAD could be made

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25. Question 25 · Easy

    In a patient with no inflammation or liver disease, which single blood test best reflects total body iron stores?

    1. ASerum iron
    2. BTotal iron-binding capacity
    3. CTransferrin saturation
    4. DSerum ferritin

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