Vitamins and Coenzymes Practice Questions

Q: Which vitamin is commonly referred to as the 'antistress' vitamin?

Vitamin B5. ***Vitamin B5*** - **Vitamin B5** (pantothenic acid) is often called the "antistress" vitamin due to its crucial role in **adrenal gland function** and the production of **stress hormones**. - It participates in the synthesis of **coenzyme A (CoA)**, essential for energy metabolism and the production of neurotransmitters. *Vitamin B1* - **Vitamin B1 (thiamine)** is vital in **carbohydrate metabolism** and nerve function, but it is not directly associated with stress management. - Deficiency leads to **beriberi**, affecting the cardiovascular and nervous systems, rather than stress adaptation. *Vitamin B2* - **Vitamin B2 (riboflavin)** is a component of **flavin coenzymes**, critical for energy production and cellular growth, but it is not primarily known for antistress effects. - Its deficiency can lead to **ariboflavinosis**, affecting skin and mucous membranes. *Vitamin B3* - **Vitamin B3 (niacin)** plays a role in energy metabolism and DNA repair, primarily known for preventing **pellagra**. - While it can influence neurotransmitters, it is not primarily referred to as the "antistress" vitamin in the same way B5 is.

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: 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: 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: 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: 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: 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

Which vitamin is commonly referred to as the 'antistress' vitamin?

Accepted Answer

Vitamin B5

Answer

Vitamin B1

Answer

Vitamin B2

Answer

Vitamin B3

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

Vitamin deficiency associated with cystic fibrosis is

Accepted Answer

K

Answer

B12

Answer

B6

Answer

C

Question 4

Headache and papilledema are features of toxicity of which vitamin?

Accepted Answer

Vitamin A

Answer

Vitamin D

Answer

Vitamin C

Answer

Vitamin E

Question 5

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 6

Which vitamin is required for conversion of serine to glycine?

Accepted Answer

Pyridoxine

Answer

Vitamin C

Answer

Vitamin B12

Answer

Thiamine (Vitamin B1)

Question 7

Deficiency of which vitamin during pregnancy predisposes to meningomyelocele?

Accepted Answer

Folic acid

Answer

Biotin

Answer

Pyridoxine

Answer

Thiamine

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

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