Water-Soluble Vitamins: B Complex and C — MCQs

10 questions

Which vitamin deficiency leads to megaloblastic anemia?

Thiamine deficiency is best diagnosed by?

A patient on a maize diet presented with diarrhea, dementia and dermatitis. Which vitamin deficiency is responsible for these features

A child was fed on a staple diet of maize for a long time. Which of the following vitamin may get deficient in his body?

Which reaction requires Vitamin B1?

A 2-year-old child with a history of eczema presents with a red, scaly rash around the mouth and extremities. A dietary history reveals excessive consumption of cow's milk. What nutritional deficiency is most likely?

Pyridoxine is required in -

A 45-year-old patient presents with joint pain and weakness and is known to have homocystinuria. Which vitamin is required in the treatment?

A patient is diagnosed with scurvy. This condition is due to a deficiency in which vitamin?

Q10

Which vitamin is primarily associated with the antioxidant properties of glutathione?

Water-Soluble Vitamins: B Complex and C Indian Medical PG Practice Questions and MCQs

Question 1: Which vitamin deficiency leads to megaloblastic anemia?

A. Riboflavin
B. Folate (Correct Answer)
C. Vitamin C
D. Niacin

Explanation: ***Folate*** - **Folate** is essential for DNA synthesis; a deficiency impairs erythrocyte maturation, leading to the production of **large, immature red blood cells** (megaloblasts) [3]. - This vitamin deficiency also presents with symptoms like **fatigue, glossitis**, and neurologic manifestations are absent unlike vitamin B12 deficiency [1]. *Riboflavin* - **Riboflavin (Vitamin B2)** deficiency can cause **normocytic anemia**, but generally not megaloblastic anemia. - Its deficiency is mainly associated with **angular stomatitis, cheilosis**, and ocular symptoms. *Vitamin C* - **Vitamin C** deficiency (scurvy) is associated with impaired collagen synthesis, leading to **gingival bleeding, petechiae**, and poor wound healing. - While it can cause some anemia, it is typically **microcytic** due to impaired iron absorption if it affects iron metabolism, not megaloblastic [2]. *Niacin* - **Niacin (Vitamin B3)** deficiency causes **pellagra**, characterized by the "3 D's": **dermatitis, diarrhea, and dementia**. - It does not directly lead to megaloblastic anemia, as it is not involved in a critical step of DNA synthesis in the same way folate is.

Question 2: Thiamine deficiency is best diagnosed by?

A. Blood thiamine level
B. Transketolase activity in blood (Correct Answer)
C. Aldolase activity in blood
D. Urinary thiamine level

Explanation: ***Transketolase activity in blood*** - **Transketolase** is a thiamine pyrophosphate (TPP)-dependent enzyme, and its activity in red blood cells is considered the **gold standard** for assessing thiamine status. - A **decrease in transketolase activity** that improves after the addition of TPP in vitro (TPP effect) is highly indicative of thiamine deficiency. *Blood thiamine level* - While a direct measure, **blood thiamine levels** can be influenced by recent dietary intake and may not accurately reflect the body's overall thiamine stores or functional deficiency. - Furthermore, measuring total blood thiamine doesn't always correlate well with the **functional status** of thiamine-dependent enzymes. *Aldolase activity in blood* - **Aldolase** is an enzyme involved in glycolysis, but its activity is **not dependent on thiamine**. - Therefore, measuring aldolase activity provides no information regarding thiamine status. *Urinary thiamine level* - **Urinary thiamine levels** primarily reflect recent thiamine intake and renal excretion rather than the body's total thiamine stores or a functional deficiency. - Low urinary thiamine can suggest deficiency, but it's **less reliable** than functional assays.

Question 3: A patient on a maize diet presented with diarrhea, dementia and dermatitis. Which vitamin deficiency is responsible for these features

A. Niacin (Correct Answer)
B. Riboflavin
C. Thiamine
D. Pyridoxine
E. Cobalamin

Explanation: ***Niacin*** - The classic presentation of **pellagra**, caused by a deficiency of **niacin (Vitamin B3)**, is characterized by the "**3 Ds**": **dermatitis**, **diarrhea**, and **dementia**. In severe cases, a fourth 'D' for death can also occur. - A **maize (corn)** staple diet is a known risk factor for niacin deficiency because maize contains niacin in a bound, non-bioavailable form (niacytin) and is low in tryptophan, a precursor to niacin. *Riboflavin* - **Riboflavin (Vitamin B2)** deficiency leads to **ariboflavinosis**, which can cause **cheilosis**, **angular stomatitis**, **glossitis**, and **seborrheic dermatitis**, but not the constellation of diarrhea, dementia, and dermatitis seen in pellagra. - It does not typically manifest with neurological or gastrointestinal symptoms as severe as those described in the question. *Thiamine* - **Thiamine (Vitamin B1)** deficiency causes **beriberi**, characterized by **neurological (dry beriberi)** or **cardiovascular (wet beriberi)** symptoms. - It can lead to **Wernicke-Korsakoff syndrome** in severe cases, which includes neurological deficits, but not the specific "3 Ds" of pellagra. *Pyridoxine* - **Pyridoxine (Vitamin B6)** deficiency can cause **neurological symptoms** such as **peripheral neuropathy**, **seizures**, and **depression**, as well as **dermatitis** and **glossitis**. - It does not present with the characteristic triad of dermatitis, diarrhea, and dementia seen in pellagra. *Cobalamin* - **Cobalamin (Vitamin B12)** deficiency causes **megaloblastic anemia** and **neurological symptoms** including **subacute combined degeneration** of the spinal cord, **peripheral neuropathy**, and **cognitive changes**. - While it can cause neurological symptoms, it does not present with the classic dermatitis and diarrhea combination seen in pellagra.

Question 4: A child was fed on a staple diet of maize for a long time. Which of the following vitamin may get deficient in his body?

A. Thiamine (Vitamin B1)
B. Vitamin B6 (Pyridoxine)
C. Cobalamin (Vitamin B12)
D. Niacin (Vitamin B3) (Correct Answer)

Explanation: ***Niacin (Vitamin B3)*** - Maize is deficient in tryptophan (an amino acid that can be converted to **niacin**) and contains niacin in a bound form (**niacytin**) that is not bioavailable. - A staple diet of maize without adequate supplementation can lead to **pellagra**, characterized by the classic triad of dermatitis, diarrhea, and dementia (3 D's). - This is particularly common in populations relying heavily on untreated maize as a staple food. *Thiamine (Vitamin B1)* - While polishing rice can remove thiamine, maize itself is not primarily associated with **thiamine deficiency** as a staple. - **Beriberi** (thiamine deficiency) presents with neurological and cardiovascular symptoms (wet and dry beriberi), distinct from pellagra. *Vitamin B6 (Pyridoxine)* - Deficiency of **pyridoxine** is uncommon with maize-based diets unless there are other contributing factors like drug interactions (e.g., isoniazid). - Symptoms include peripheral neuropathy, seborrheic dermatitis, and sideroblastic anemia, which are not directly linked to a maize staple diet. *Cobalamin (Vitamin B12)* - **Vitamin B12** is found primarily in animal products, so a vegetarian or vegan diet poses a risk for deficiency, not specifically a maize-based diet. - Deficiency leads to megaloblastic anemia and neurological damage (subacute combined degeneration), unrelated to maize's nutritional profile.

Question 5: Which reaction requires Vitamin B1?

A. None of the options
B. Oxidative decarboxylation (Correct Answer)
C. Carboxylation
D. Transamination

Explanation: ***Oxidative decarboxylation*** - Vitamin B1, in its active form **thiamine pyrophosphate (TPP)**, is a crucial coenzyme for enzymes catalyzing **oxidative decarboxylation** reactions. - Key examples include the **pyruvate dehydrogenase complex** and **alpha-ketoglutarate dehydrogenase complex**, essential for cellular respiration and the citric acid cycle. *Transamination* - This type of reaction, involving the transfer of an **amino group**, primarily requires **pyridoxal phosphate (PLP)**, the active form of **Vitamin B6**. - It is vital for amino acid metabolism but does not utilize Vitamin B1. *Carboxylation* - **Carboxylation** reactions, which add a carboxyl group to a substrate, typically require **biotin** (Vitamin B7) as a coenzyme. - Examples include pyruvate carboxylase and acetyl-CoA carboxylase, which are not dependent on Vitamin B1. *None of the options* - As **oxidative decarboxylation** specifically requires Vitamin B1, this option is incorrect. - The other listed reactions depend on different vitamins as coenzymes.

Question 6: A 2-year-old child with a history of eczema presents with a red, scaly rash around the mouth and extremities. A dietary history reveals excessive consumption of cow's milk. What nutritional deficiency is most likely?

A. Zinc deficiency (Correct Answer)
B. Iron deficiency
C. Vitamin D deficiency
D. Vitamin C deficiency

Explanation: ***Zinc deficiency*** - The combination of **eczema**, perioral and acral **dermatitis** (red, scaly rash around the mouth and extremities), and a diet rich in **cow's milk** in a 2-year-old strongly points to zinc deficiency. - Cow's milk can inhibit **zinc absorption**, and infants with eczema may have increased zinc demands or impaired absorption. *Iron deficiency* - While common in toddlers, especially with high cow's milk intake, **iron deficiency** primarily manifests as **anemia**, pallor, and fatigue, not a characteristic rash. - It does not typically cause the specific **dermatitis** described. *Vitamin D deficiency* - Primarily linked to **rickets** in children, causing bone deformities and growth delays. - Does not present with a **red, scaly rash** around the mouth and extremities. *Vitamin C deficiency* - Leads to **scurvy**, characterized by swollen, bleeding gums, perifollicular hemorrhages, and poor wound healing. - The described **dermatological symptoms** are not typical of vitamin C deficiency.

Question 7: Pyridoxine is required in -

A. Glycolysis
B. TCA cycle
C. Glycogenesis
D. Transamination (Correct Answer)

Explanation: ***Transamination*** - **Pyridoxal phosphate (PLP)**, the active form of pyridoxine (vitamin B6), is an essential **coenzyme for aminotransferases (transaminases)** - Transamination reactions involve the transfer of an **amino group** from an amino acid to a keto acid, which is crucial for amino acid metabolism - This is the classic biochemical function of vitamin B6 and a frequently tested concept *Glycolysis* - Glycolysis is a metabolic pathway that breaks down glucose into pyruvate - Key cofactors for glycolysis include **NAD+ and ATP**, not vitamin B6 - Does not require pyridoxine as a coenzyme *TCA cycle* - The **TCA cycle (Krebs cycle)** is a central metabolic pathway for energy production - Uses enzymes that require cofactors such as **NAD+, FAD, and Coenzyme A** (derived from pantothenic acid) - Pyridoxine is not directly involved as a coenzyme in TCA cycle reactions *Glycogenesis* - Glycogenesis is the process of synthesizing **glycogen from glucose** - Primarily involves enzymes like **glycogen synthase** and **branching enzyme** - Requires **UTP and glucose-1-phosphate**, not pyridoxine

Question 8: A 45-year-old patient presents with joint pain and weakness and is known to have homocystinuria. Which vitamin is required in the treatment?

A. Vitamin B6 (Correct Answer)
B. Vitamin B12
C. Vitamin B7
D. Vitamin B1
E. Vitamin B9

Explanation: ***Vitamin B6*** - **Homocystinuria** is often caused by a deficiency in the enzyme **cystathionine beta-synthase**, which requires **pyridoxal phosphate (active form of B6)** as a cofactor. - Supplementation with high-dose **vitamin B6** can help some patients by increasing the residual activity of the enzyme, thereby reducing **homocysteine levels**. - This is the **primary treatment** for **B6-responsive homocystinuria** (approximately 50% of cases respond to B6 therapy). *Vitamin B12* - Vitamin B12 is a cofactor for the enzyme **methionine synthase**, which converts homocysteine back to methionine. - While it plays a role in homocysteine metabolism, **vitamin B6** is typically the primary treatment for homocystinuria caused by **cystathionine beta-synthase deficiency**. *Vitamin B9* - Vitamin B9 (folic acid) works together with **vitamin B12** as a cofactor in the **remethylation pathway** via methionine synthase. - While folate supplementation may help lower homocysteine levels, it is **not the primary treatment** for classical homocystinuria due to cystathionine beta-synthase deficiency. - **Vitamin B6** remains the first-line vitamin therapy for enzyme deficiency-related homocystinuria. *Vitamin B7* - Vitamin B7, or **biotin**, is a cofactor for carboxylase enzymes and is involved in fatty acid synthesis and gluconeogenesis. - It has no direct role in the metabolism of **homocysteine** or the treatment of homocystinuria. *Vitamin B1* - Vitamin B1, or **thiamine**, is essential for carbohydrate metabolism and nerve function. - It is not involved in the metabolic pathways that regulate **homocysteine levels** or the treatment of homocystinuria.

Question 9: A patient is diagnosed with scurvy. This condition is due to a deficiency in which vitamin?

A. Vitamin A
B. Vitamin C (Correct Answer)
C. Vitamin D
D. Vitamin E

Explanation: ***Vitamin C*** - **Scurvy** is directly caused by a prolonged and severe deficiency of **Vitamin C (ascorbic acid)**. - Vitamin C is essential for **collagen synthesis**, and its deficiency leads to impaired wound healing, fragile blood vessels, and gum disease, which are hallmarks of scurvy. *Vitamin A* - Deficiency in Vitamin A primarily causes **vision problems**, such as night blindness, and can lead to xerophthalmia, but not scurvy. - It plays a crucial role in **immune function** and cell growth, distinguishing its role from collagen synthesis. *Vitamin D* - A deficiency in Vitamin D is associated with **rickets** in children and **osteomalacia** in adults, conditions primarily affecting bone mineralization. - It is vital for **calcium and phosphate absorption**, which is unrelated to the collagen defects seen in scurvy. *Vitamin E* - Deficiency in Vitamin E is rare and can lead to **neurological symptoms** like ataxia and peripheral neuropathy. - It acts as a **powerful antioxidant**, protecting cells from oxidative damage, which is a different metabolic pathway than Vitamin C's role in collagen.

Question 10: Which vitamin is primarily associated with the antioxidant properties of glutathione?

A. Vitamin E
B. Niacin (Correct Answer)
C. Vitamin C
D. Vitamin A

Explanation: ***Niacin*** - **Niacin** (Vitamin B3) is the vitamin most directly associated with glutathione's antioxidant properties - Niacin is a precursor to **NAD+** and **NADP+**, which are converted to **NADPH** - **NADPH is the essential cofactor** for **glutathione reductase**, the primary enzyme that reduces oxidized glutathione (GSSG) back to its active reduced form (GSH) - This NADPH-dependent enzymatic pathway is the **main mechanism** for maintaining the body's glutathione antioxidant system - Without adequate niacin → NADPH, glutathione cannot be efficiently regenerated *Vitamin C* - **Vitamin C** can non-enzymatically reduce GSSG to GSH, providing a **secondary backup mechanism** - While vitamin C does support glutathione regeneration, this is an **indirect, non-enzymatic process** - It acts as an antioxidant itself but is not the primary vitamin associated with glutathione's antioxidant function *Vitamin E* - **Vitamin E** is a **lipid-soluble antioxidant** that primarily protects cell membranes from oxidative damage - Works synergistically with other antioxidants but has **no direct role** in glutathione synthesis or regeneration *Vitamin A* - **Vitamin A** (retinol) is crucial for vision, immune function, and cell differentiation - Has some antioxidant properties as a carotenoid derivative but **no direct involvement** in glutathione metabolism

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