Vitamins and Coenzymes Practice Questions

Q: Headache and papilledema are features of toxicity of which vitamin?

Vitamin A. ***Vitamin A*** - **Vitamin A toxicity** (hypervitaminosis A) can lead to increased **intracranial pressure**, manifesting as **headache** and **papilledema**. - Other symptoms may include **dry skin**, **cheilosis**, **hepatomegaly**, and **bone pains**. *Vitamin D* - **Vitamin D toxicity** is primarily characterized by **hypercalcemia**, which can lead to symptoms like **nausea**, **vomiting**, **polyuria**, and **renal stones**. - It does not typically cause papilledema or increased intracranial pressure directly. *Vitamin C* - **Vitamin C toxicity** is rare due to its water-soluble nature, but very high doses can cause **gastrointestinal upset** (diarrhea) and **kidney stones**. - It is not associated with neurological symptoms like headache or papilledema. *Vitamin E* - **Vitamin E toxicity** is uncommon, but high doses can interfere with **blood clotting** and increase the risk of **bleeding**, especially in patients taking anticoagulants. - It is not associated with increased intracranial pressure or papilledema.

Q: Which of the following vitamins is significantly synthesised in gut by intestinal flora?

Biotin. ***Biotin*** - **Biotin (Vitamin B7)** can be synthesized by **intestinal flora** in humans, contributing to the body's overall supply. - While dietary intake is the primary source, **gut bacteria** play a significant role in its endogenous production. *Folate* - Although some bacteria can synthesize **folate**, the human body primarily relies on **dietary intake** and absorption in the small intestine. - The contribution of gut flora to human folate requirements is generally considered **minor** and insufficient to meet daily needs. *B12* - **Vitamin B12 (cobalamin)** is exclusively synthesized by **microorganisms**, but in humans, this synthesis occurs mainly in the colon, where absorption is limited. - Humans must obtain **B12** from **animal products** or fortified foods, as intestinal flora synthesis does not contribute significantly to usable amounts. *B6* - **Vitamin B6 (pyridoxine)** is primarily obtained through **dietary sources** such as meat, fish, and vegetables. - The synthesis of **B6** by intestinal flora is **negligible** and does not contribute meaningfully to human requirements.

Q: Deficiency of which vitamin during pregnancy predisposes to meningomyelocele?

Folic acid. ***Folic acid*** - **Folic acid** (Vitamin B9) is crucial for **neural tube closure** during early embryonic development. - Deficiency leads to neural tube defects such as **meningomyelocele** and **anencephaly**. *Biotin* - **Biotin** (Vitamin B7) plays a role in **metabolism** of carbohydrates, fats, and proteins. - Deficiency is rare and not primarily associated with neural tube defects. *Pyridoxine* - **Pyridoxine** (Vitamin B6) is important for amino acid metabolism and neurotransmitter synthesis but not directly linked to neural tube closure. - Deficiency can lead to **neurological symptoms** and **anemia**. *Thiamine* - **Thiamine** (Vitamin B1) is essential for energy metabolism and nerve function. - Deficiency causes **beriberi** and is not associated with neural tube defects.

Q: Vitamin B12 is required for all of the following processes except?

Conversion of homocysteine to cysteine. ***Conversion of homocysteine to cysteine*** - The conversion of **homocysteine to cysteine** involves two enzymes: **cystathionine beta-synthase (CBS)** and **cystathionine gamma-lyase (CTH)**. These enzymes require **vitamin B6** (pyridoxal phosphate) as a cofactor, not vitamin B12. - This pathway is part of the **transsulfuration pathway**, which is critical for homocysteine metabolism and cysteine synthesis. *Synthesis of thymidine* - **Vitamin B12**, as a cofactor for **methionine synthase**, is indirectly involved in the synthesis of **tetrahydrofolate**, which is essential for the production of **thymidylate** (a precursor to thymidine) from dUDP. - Deficiency in vitamin B12 can lead to a "folate trap," impairing DNA synthesis and causing **megaloblastic anemia**. *Isomerization of methylmalonyl-CoA* - **Methylmalonyl-CoA mutase**, an enzyme directly requiring **vitamin B12** (specifically, 5'-deoxyadenosylcobalamin), catalyzes the isomerization of **methylmalonyl-CoA to succinyl-CoA**. - This reaction is crucial for the metabolism of odd-chain fatty acids and certain amino acids, and its impairment in B12 deficiency leads to the accumulation of **methylmalonic acid**. *Conversion of homocysteine to methionine* - The enzyme **methionine synthase** (also known as homocysteine methyltransferase) catalyzes the conversion of **homocysteine to methionine**, using **vitamin B12** (specifically, methylcobalamin) as a coenzyme. - This reaction also requires **methylenetetrahydrofolate reductase** (MTHFR) and is critical for both homocysteine metabolism and the regeneration of **tetrahydrofolate**.

Q: Which vitamin is required for conversion of serine to glycine?

Pyridoxine. ***Pyridoxine*** - **Pyridoxine (Vitamin B6)** is a crucial cofactor for the enzyme **serine hydroxymethyltransferase**, which catalyzes the reversible conversion of **serine to glycine and 5,10-methylenetetrahydrofolate**. - This reaction requires **pyridoxal phosphate (PLP)**, the active form of vitamin B6, emphasizing its role in **amino acid metabolism** and one-carbon unit transfer. *Vitamin C* - **Vitamin C** (ascorbic acid) is primarily involved in **collagen synthesis**, acting as a cofactor for hydroxylase enzymes. - It also functions as an **antioxidant** and is essential for immune function, but not directly in the serine-glycine interconversion. *Vitamin B12* - **Vitamin B12** (cobalamin) is a cofactor for enzymes involved in two main reactions: the conversion of **methylmalonyl CoA to succinyl CoA** and the synthesis of **methionine from homocysteine**. - It is not directly involved in the conversion of serine to glycine. *Thiamine (Vitamin B1)* - **Thiamine (Vitamin B1)** is critical for carbohydrate metabolism, acting as a cofactor for enzymes like **pyruvate dehydrogenase** and **α-ketoglutarate dehydrogenase**. - It plays no direct role in the metabolic pathway linking serine and glycine.

Q: Vitamin deficiency associated with cystic fibrosis is

K. ***K*** - Cystic fibrosis is characterized by **exocrine pancreatic insufficiency**, leading to malabsorption of fats and fat-soluble vitamins (A, D, E, K) [1]. - **Vitamin K** is crucial for coagulation; its deficiency can lead to **bleeding disorders**, which is a concern in CF patients [1]. *B6* - **Vitamin B6 (pyridoxine)** deficiency is not a primary or common deficiency directly linked to the malabsorptive issues in cystic fibrosis [2]. - While general malnutrition can occur, there isn't a specific mechanism in CF that predominantly targets B6 absorption [2]. *C* - **Vitamin C (ascorbic acid)** is a water-soluble vitamin, and its absorption is generally not significantly impaired in cystic fibrosis. - Malabsorption in CF primarily affects fat and fat-soluble substances due to pancreatic enzyme deficiency [1]. *B12* - While **Vitamin B12** malabsorption can occur in some gastrointestinal disorders, it is not a primary or specific vitamin deficiency associated with the typical pancreatic insufficiency in cystic fibrosis. - B12 absorption requires intrinsic factor and an intact ileum, which are not directly affected by the exocrine pancreatic dysfunction in CF.

Q: Which of the following statements about NAD and NADP is true?

Niacin is a major precursor for NAD and NADP synthesis. ***Niacin is a major precursor for NAD and NADP synthesis*** - **Niacin**, also known as vitamin B3, is a crucial nutrient required for the biosynthesis of both **nicotinamide adenine dinucleotide (NAD)** and **nicotinamide adenine dinucleotide phosphate (NADP)**. - The body converts niacin into these coenzymes, essential for numerous **redox reactions** in metabolism. *High leucine intake directly inhibits NAD synthesis* - While high intake of certain **amino acids** can affect metabolic pathways, **leucine** specifically is known to inhibit the activity of **kynureninase**, an enzyme in the kynurenine pathway which is involved in niacin synthesis from tryptophan. - However, it does not directly inhibit the synthesis of NAD itself but rather impacts a pathway leading to one of its precursors, which is distinct from a direct inhibition of NAD synthesis. *All isoforms of malic enzyme exclusively use NAD as cofactor* - **Malic enzyme** is a family of enzymes that catalyze the oxidative decarboxylation of malate to pyruvate. - Different isoforms exist: **ME1 (cytosolic)** uses **NADP**, while **ME2 and ME3 (mitochondrial)** use **NAD**; thus, not all isoforms exclusively use NAD. *NAD and NADP deficiency symptoms include dermatitis and dementia* - The symptoms of **dermatitis** and **dementia**, along with diarrhea, are characteristic of **pellagra**, a disease caused by severe **niacin (vitamin B3) deficiency**. - While NAD and NADP are derived from niacin, the deficiency symptoms are attributed to the lack of the precursor molecule, niacin, rather than a direct deficiency of NAD and NADP as separate entities.

Q: Subacute combined degeneration of cord is caused due to deficiency of

Vitamin B12. ***Vitamin B12*** - **Subacute combined degeneration of the spinal cord** is a classic neurological complication directly resulting from severe and prolonged **Vitamin B12 (cobalamin)** deficiency. - This deficiency leads to impaired **myelin synthesis** and maintenance, primarily affecting the **posterior** and **lateral columns** of the spinal cord. *Vitamin B1* - Deficiency of **Vitamin B1 (thiamine)** is associated with **beriberi** and **Wernicke-Korsakoff syndrome**, affecting the peripheral nervous system and brain, but not typically causing subacute combined degeneration [2]. - Symptoms usually include **peripheral neuropathy**, **cardiac dysfunction**, or **encephalopathy**, distinct from spinal cord degeneration [2]. *Vitamin B5* - **Vitamin B5 (pantothenic acid)** is involved in **coenzyme A (CoA)** synthesis, crucial for metabolism. - Its deficiency is extremely rare and can cause symptoms like **paresthesia** and **fatigue**, but not specific spinal cord degeneration. *Vitamin B6* - **Vitamin B6 (pyridoxine)** deficiency predominantly affects the **peripheral nervous system**, leading to **neuropathy** and seizures [1]. - While essential for nervous system function, it does not cause the characteristic pattern of demyelination seen in subacute combined degeneration of the cord [1].

Q: Which of the following is not a good source of vitamin C?

Egg. ***Egg*** - Eggs are a good source of **protein**, **choline**, **vitamins B12 and D**, but contain **negligible amounts of vitamin C**. - Vitamin C is primarily found in **fruits and vegetables**. *Amla* - **Amla** (Indian gooseberry) is an exceptionally rich source of **vitamin C**, often used in traditional medicine for its high content. - It contains significantly more vitamin C than many other fruits, making it a powerful antioxidant. *Lime* - **Lime**, like other citrus fruits, is an excellent source of **vitamin C**, contributing to immune function and collagen synthesis. - A single lime can provide a substantial portion of the recommended daily intake of vitamin C. *Guava* - **Guava** is remarkably rich in **vitamin C**, often containing several times the amount found in oranges. - It also provides fiber and other antioxidants, making it a highly nutritious fruit.

Q: Recommended daily dietary requirement of folate (folic acid) in infants (7-12 months)?

80-120 μg. ***80-120 μg*** * This range represents the **adequate intake for infants aged 7-12 months**, supporting normal growth, erythropoiesis, and **DNA synthesis**. * The RDA for this age group is **80 μg/day**, and the range up to 120 μg provides a safety margin for individual variation. * This requirement increases with age as children grow and develop. *200 μg* * This amount represents the RDA for **older children (4-8 years)**, not for infants in the 7-12 month age range. * While safe, it exceeds the typical needs for infants and is unnecessary as a daily target for this age group. *400 μg* * This dosage is the RDA for **adolescents (14-18 years)** and is also recommended for **women of childbearing age** to prevent neural tube defects. * For infants aged 7-12 months, this would be approximately 5 times the recommended amount and is excessive. *600 μg* * This represents the **upper tolerable limit** for adolescents and adults, not a recommended daily requirement. * Such a high dose for infants is inappropriate and could potentially mask **vitamin B12 deficiency** or cause other complications.

Question 1

Headache and papilledema are features of toxicity of which vitamin?

Accepted Answer

Vitamin A

Answer

Vitamin D

Answer

Vitamin C

Answer

Vitamin E

Question 2

Which of the following vitamins is significantly synthesised in gut by intestinal flora?

Accepted Answer

Biotin

Answer

B12

Answer

B6

Answer

Folate

Question 3

Deficiency of which vitamin during pregnancy predisposes to meningomyelocele?

Accepted Answer

Folic acid

Answer

Biotin

Answer

Pyridoxine

Answer

Thiamine

Question 4

Vitamin B12 is required for all of the following processes except?

Accepted Answer

Conversion of homocysteine to cysteine

Answer

Synthesis of thymidine

Answer

Isomerization of methylmalonyl-CoA

Answer

Conversion of homocysteine to methionine

Question 5

Which vitamin is required for conversion of serine to glycine?

Accepted Answer

Pyridoxine

Answer

Vitamin C

Answer

Vitamin B12

Answer

Thiamine (Vitamin B1)

Question 6

Vitamin deficiency associated with cystic fibrosis is

Accepted Answer

K

Answer

B12

Answer

B6

Answer

C

Question 7

Which of the following statements about NAD and NADP is true?

Accepted Answer

Niacin is a major precursor for NAD and NADP synthesis

Answer

High leucine intake directly inhibits NAD synthesis

Answer

All isoforms of malic enzyme exclusively use NAD as cofactor

Answer

NAD and NADP deficiency symptoms include dermatitis and dementia

Question 8

Subacute combined degeneration of cord is caused due to deficiency of

Accepted Answer

Vitamin B12

Answer

Vitamin B1

Answer

Vitamin B5

Answer

Vitamin B6

Question 9

Which of the following is not a good source of vitamin C?

Accepted Answer

Egg

Answer

Amla

Answer

Lime

Answer

Guava

Question 10

Recommended daily dietary requirement of folate (folic acid) in infants (7-12 months)?

Accepted Answer

80-120 μg

Answer

200 μg

Answer

400 μg

Answer

600 μg

Vitamins and Coenzymes — MCQs

Vitamins and Coenzymes — MCQs

On this page

Practice by Chapter

Want unlimited practice?