Vitamins and Coenzymes Practice Questions

Q: Which vitamin deficiency is most commonly responsible for this condition?

Vitamin B2. ***Vitamin B2*** - **Riboflavin deficiency** classically causes **angular stomatitis** (cracks at corners of mouth) and **cheilosis** (lip inflammation), which are the characteristic oral manifestations. - Also presents with **glossitis**, **seborrheic dermatitis**, and **corneal vascularization**, making it the most likely cause of mucocutaneous findings. *Vitamin B1* - **Thiamine deficiency** primarily causes **Wernicke's encephalopathy** (confusion, ataxia, ophthalmoplegia) and **beriberi** (heart failure, peripheral neuropathy). - Does not typically cause **oral or skin manifestations** like angular stomatitis or cheilosis. *Niacin* - **Niacin deficiency** causes **pellagra** with the classic **4 Ds**: dermatitis, diarrhea, dementia, and death. - Skin changes are typically **photosensitive dermatitis** on sun-exposed areas, not angular stomatitis or mucocutaneous lesions. *Vitamin B12* - **Cobalamin deficiency** primarily causes **megaloblastic anemia** and **subacute combined degeneration** of the spinal cord. - Neurological symptoms include **peripheral neuropathy** and **cognitive impairment**, but oral manifestations are rare.

Q: Which of the following is NOT a form of Vitamin K?

Phytoquinone. **Explanation:** Vitamin K is a group of fat-soluble vitamins essential for the post-translational modification of certain proteins, most notably clotting factors II, VII, IX, and X. The nomenclature of Vitamin K is a high-yield topic for NEET-PG. **Why "Phytoquinone" is the correct answer:** There is no naturally occurring or synthetic form of Vitamin K named "Phytoquinone." This is a distractor term often confused with **Phylloquinone**. While "Phyto-" refers to plants, the correct chemical name for Vitamin K1 is Phylloquinone. **Analysis of other options:** * **Phytonadione (Option C):** This is the pharmaceutical name for **Vitamin K1 (Phylloquinone)**. It is the primary dietary form found in green leafy vegetables. * **Menaquinone (Option A):** Also known as **Vitamin K2**, it is synthesized by intestinal bacterial flora. It is the form found in fermented foods and animal products. * **Menadione (Option B):** This is **Vitamin K3**, a synthetic, water-soluble precursor. It is no longer used clinically in humans due to the risk of hemolytic anemia and neonatal jaundice (kernicterus). **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Vitamin K acts as a coenzyme for **gamma-glutamyl carboxylase**, which carboxylates glutamate residues on clotting factors. * **Warfarin Interaction:** Warfarin inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K and thus inhibiting the activation of factors II, VII, IX, and X. * **Newborn Prophylaxis:** Neonates are born with sterile guts and low Vitamin K stores; hence, a prophylactic IM injection of Vitamin K1 is given at birth to prevent **Hemorrhagic Disease of the Newborn**.

Q: Which vitamin deficiency disorder is associated with a diet primarily consisting of cereals?

Pellagra. **Explanation:** **Pellagra** is caused by a deficiency of **Niacin (Vitamin B3)** or its precursor, the amino acid **Tryptophan**. A diet primarily consisting of cereals, specifically **Maize (Corn)** or **Sorghum (Jowar)**, is the classic trigger for this condition. * **Maize:** Contains niacin in a bound, unabsorbable form called **niacytin**. It is also deficient in Tryptophan. * **Sorghum:** Contains high levels of the amino acid **Leucine**, which interferes with the conversion of Tryptophan to Niacin by inhibiting the enzyme *Quinolinate Phosphoribosyl Transferase (QPRT)*. **Analysis of Incorrect Options:** * **A. Scurvy:** Caused by Vitamin C deficiency; typically associated with a lack of fresh fruits and vegetables, not cereal-based diets. * **B. Beriberi:** Caused by Thiamine (B1) deficiency; classically associated with a diet of **polished rice**, where the thiamine-rich outer layer (bran) is removed. * **D. Pyridoxine (B6) deficiency:** Usually secondary to drugs (like Isoniazid) or alcoholism rather than a primary cereal-based dietary pattern. **Clinical Pearls for NEET-PG:** * **The 4 D’s of Pellagra:** Dermatitis (Casal’s necklace distribution), Diarrhea, Dementia, and Death. * **Hartnup Disease:** An autosomal recessive disorder causing defective transport of neutral amino acids (Tryptophan), leading to pellagra-like symptoms. * **Carcinoid Syndrome:** Can lead to secondary niacin deficiency because Tryptophan is diverted to produce excessive Serotonin. * **Conversion Ratio:** 60 mg of dietary Tryptophan yields 1 mg of Niacin.

Q: Which of the following vitamins does not play any role in the process of tooth development?

Vitamin E. **Explanation:** Tooth development (odontogenesis) is a complex process requiring specific vitamins for the formation and mineralization of the organic matrix. **Vitamin E** (Tocopherol) primarily functions as a potent lipid-soluble antioxidant that protects cell membranes from free radical damage. While essential for reproductive health and neurological function, it has **no direct role** in the structural development or mineralization of teeth. **Why the other options are incorrect:** * **Vitamin A (Retinol):** Essential for the differentiation of epithelial cells. In the oral cavity, it is crucial for the differentiation of **ameloblasts** (enamel-forming cells). Deficiency leads to enamel hypoplasia and defective dentin formation. * **Vitamin C (Ascorbic Acid):** Required for the post-translational hydroxylation of proline and lysine residues in **collagen synthesis**. Since dentin, cementum, and the periodontal ligament are collagen-rich structures, Vitamin C is vital for their integrity. Deficiency causes scurvy, characterized by swollen gums and mobile teeth. * **Vitamin D (Cholecalciferol):** Regulates calcium and phosphorus homeostasis. It is essential for the **mineralization** of the enamel and dentin matrix. Deficiency during tooth development leads to delayed eruption and poorly mineralized (hypocalcified) enamel. **NEET-PG High-Yield Pearls:** * **Ameloblasts** (Enamel) = Vitamin A dependent. * **Odontoblasts** (Dentin/Collagen) = Vitamin C dependent. * **Mineralization** = Vitamin D and Calcium dependent. * **Vitamin K** is also involved in tooth development via the gamma-carboxylation of osteocalcin, which binds calcium in the matrix.

Q: Niacin deficiency causes all of the following except?

Dactylitis. **Explanation:** The question tests your knowledge of **Pellagra**, the clinical manifestation of **Niacin (Vitamin B3)** deficiency. **1. Why Dactylitis is the correct answer:** Dactylitis refers to the "sausage-like" swelling of fingers or toes. It is typically associated with conditions like Sickle Cell Anemia (Hand-foot syndrome), Psoriatic Arthritis, or Sarcoidosis. It has no physiological or clinical link to Niacin deficiency. **2. Why the other options are incorrect (The 3 Ds of Pellagra):** Niacin is a precursor for NAD and NADP, which are essential for redox reactions and DNA repair. Deficiency leads to Pellagra, characterized by the classic triad: * **Dermatitis (Option A):** Characteristically presents as a symmetrical, photosensitive scaly rash. A high-yield sign is **Casal’s necklace**, a ring of dermatitis around the lower neck. * **Diarrhoea (Option C):** Caused by atrophy of the columnar epithelium of the GI tract mucosa, leading to malabsorption and inflammation. * **Dementia (Option D):** Represents neurological involvement, including irritability, poor concentration, and eventually overt dementia or encephalopathy. If untreated, a 4th "D"—**Death**—occurs. **High-Yield Clinical Pearls for NEET-PG:** * **Tryptophan Connection:** Niacin can be synthesized from the amino acid Tryptophan (**60 mg Tryptophan = 1 mg Niacin**). This requires Vitamin **B6 (Pyridoxine)** as a cofactor. * **Hartnup Disease:** A genetic defect in neutral amino acid transport (Tryptophan) that leads to Pellagra-like symptoms. * **Carcinoid Syndrome:** Diversion of Tryptophan to serotonin synthesis can lead to secondary Niacin deficiency. * **Corn/Maize Diets:** Diets primary in maize are pellagragenic because Niacin is present in a bound, unabsorbable form (**Niacytin**).

Q: Which one of the following is not a cause of vitamin B12 deficiency?

Resection of ascending colon.. **Explanation:** Vitamin B12 (Cobalamin) absorption is a complex process requiring specific anatomical sites and physiological factors. The correct answer is **D (Resection of ascending colon)** because Vitamin B12 is primarily absorbed in the **terminal ileum**. The ascending colon is involved in water and electrolyte absorption, not B12 uptake; therefore, its removal does not cause B12 deficiency. **Analysis of Options:** * **A. Blind-loop syndrome:** This involves bacterial overgrowth in a stagnant segment of the intestine. These bacteria (e.g., *E. coli*) compete with the host for Vitamin B12, leading to deficiency. * **B. Dietary deficiency:** B12 is synthesized exclusively by microorganisms and found only in animal products (meat, eggs, dairy). Strict vegans are at high risk of dietary deficiency. * **C. Intrinsic factor (IF) deficiency:** IF is secreted by gastric parietal cells and is essential for B12 absorption in the ileum. Deficiency occurs in Pernicious Anemia (autoimmune destruction of parietal cells) or after a gastrectomy. **High-Yield NEET-PG Pearls:** * **Absorption Pathway:** B12 binds to **R-binder** (saliva) → released by pancreatic proteases → binds to **Intrinsic Factor** (stomach) → absorbed in the **Terminal Ileum** via cubilin receptors → transported in blood by **Transcobalamin II**. * **Storage:** Unlike other water-soluble vitamins, B12 is stored in the **liver** for 3–5 years. * **Diagnostic Test:** The **Schilling test** (though largely historical) was used to differentiate causes of B12 malabsorption. * **Clinical Marker:** B12 deficiency leads to increased levels of **Methylmalonic acid (MMA)** and Homocysteine.

Q: Vitamin-B12 deficiency is not seen in which of the following conditions?

Resection of jejunum. **Explanation:** The absorption of Vitamin B12 (Cobalamin) is a complex process requiring specific anatomical sites and physiological secretions. The correct answer is **Resection of jejunum** because the jejunum is not involved in the specific absorption pathway of Vitamin B12. **1. Why Resection of Jejunum is the correct answer:** Vitamin B12 absorption occurs exclusively in the **terminal ileum**. While the jejunum is the primary site for the absorption of most nutrients (including Folate), its removal does not directly impair B12 status, provided the ileum and stomach remain functional. **2. Why the other options are incorrect:** * **Resection of ileum:** The terminal ileum contains the specific receptors (cubilin) required for the uptake of the B12-Intrinsic Factor (IF) complex. Its removal leads to definitive malabsorption. * **Achlorhydria:** Gastric acid and pepsin are essential to release Vitamin B12 from dietary animal proteins. Without acid, B12 remains bound to food proteins and cannot bind to R-binders or Intrinsic Factor. * **Parietal cell destruction:** Parietal cells in the gastric mucosa secrete **Intrinsic Factor (IF)**. Destruction of these cells (as seen in Pernicious Anemia or Gastritis) prevents the formation of the B12-IF complex, making absorption impossible. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Absorption:** Folate = Jejunum; Vitamin B12 = Terminal Ileum ("**F**irst **J**unction, **L**ast **I**leum"). * **Transport Proteins:** Transcobalamin II is the primary physiological transporter that delivers B12 to tissues. * **Diagnostic Test:** The Schilling test (though largely historical) was used to differentiate between the causes of B12 deficiency mentioned above. * **Metabolic Markers:** B12 deficiency leads to increased levels of both **Homocysteine** and **Methylmalonic Acid (MMA)**; Folate deficiency only increases Homocysteine.

Q: Which vitamin is essential for the metabolism of sulfur-containing amino acids?

Folic acid. **Explanation:** **Folic acid (Vitamin B9)** is the correct answer because it plays a pivotal role in the **one-carbon metabolism** required for the processing of sulfur-containing amino acids, specifically **Methionine and Homocysteine**. Tetrahydrofolate (THF) acts as a carrier of one-carbon units. In the methionine cycle, 5-methyl THF donates a methyl group to homocysteine to regenerate methionine (a reaction catalyzed by methionine synthase, requiring Vitamin B12 as a co-factor). Without folic acid, homocysteine cannot be remethylated, leading to hyperhomocysteinemia. **Analysis of Incorrect Options:** * **Biotin (B7):** Acts as a co-enzyme for **carboxylation** reactions (e.g., Pyruvate carboxylase, Acetyl-CoA carboxylase). It is not involved in the sulfur-amino acid pathway. * **Vitamin C (Ascorbic acid):** Primarily functions as an antioxidant and a co-factor for **hydroxylation** of proline and lysine in collagen synthesis. * **Thiamine (B1):** Serves as a co-enzyme for **oxidative decarboxylation** (e.g., Pyruvate dehydrogenase) and transketolase in the HMP shunt. **High-Yield Clinical Pearls for NEET-PG:** * **The Homocysteine Connection:** Three vitamins are essential for homocysteine metabolism: **B9 (Folate)** and **B12** (for remethylation to methionine) and **B6 (Pyridoxine)** (for the cystathionine pathway). * **Deficiency:** Folic acid deficiency is the most common cause of **Megaloblastic anemia** and is strongly linked to **Neural Tube Defects (NTDs)** in newborns. * **Drug Link:** Methotrexate inhibits **Dihydrofolate Reductase (DHFR)**, halting the regeneration of active THF and disrupting amino acid and DNA synthesis.

Question 1

Which vitamin deficiency is most commonly responsible for this condition?

Accepted Answer

Vitamin B2

Answer

Vitamin B1

Answer

Niacin

Answer

Vitamin B12

Question 2

Which of the following is NOT a form of Vitamin K?

Accepted Answer

Phytoquinone

Answer

Menoquinone

Answer

Menadione

Answer

Phytonadione

Question 3

Which nutritional deficiency is associated with hereditary ataxia?

Accepted Answer

Vitamin E

Answer

Vitamin B12

Answer

Vitamin B1

Answer

Vitamin C

Question 4

Which vitamin deficiency disorder is associated with a diet primarily consisting of cereals?

Accepted Answer

Pellagra

Answer

Scurvy

Answer

Beriberi

Answer

Pyridoxine deficiency

Question 5

Which of the following vitamins does not play any role in the process of tooth development?

Accepted Answer

Vitamin E

Answer

Vitamin A

Answer

Vitamin C

Answer

Vitamin D

Question 6

Niacin deficiency causes all of the following except?

Accepted Answer

Dactylitis

Answer

Dermatitis

Answer

Diarrhoea

Answer

Dementia

Question 7

Which one of the following is not a cause of vitamin B12 deficiency?

Accepted Answer

Resection of ascending colon.

Answer

Blind-loop syndrome.

Answer

Dietary deficiency.

Answer

Intrinsic factor deficiency.

Question 8

Pyridoxal phosphate is a key cofactor in metabolism. Which of the following reactions requires this cofactor?

Accepted Answer

Glycogen converted to Glucose-1-Phosphate - yes; Pyruvate plus aspartate producing alanine and oxaloacetate - yes; Homocysteine plus N5-Methyl-THF produces methionine and THF - no; Homocysteine plus serine produces cystathionine - yes; Histidine produces histamine - yes

Answer

Glycogen converted to Glucose-1-Phosphate - yes; Pyruvate plus aspartate producing alanine and oxaloacetate - yes; Homocysteine plus N5-Methyl-THF produces methionine and THF - yes; Homocysteine plus serine produces cystathionine - no; Histidine produces histamine - yes

Answer

Glycogen converted to Glucose-1-Phosphate - yes; Pyruvate plus aspartate producing alanine and oxaloacetate - yes; Homocysteine plus N5-Methyl-THF produces methionine and THF - no; Homocysteine plus serine produces cystathionine - yes; Histidine produces histamine - no

Answer

Glycogen converted to Glucose-1-Phosphate - yes; Pyruvate plus aspartate producing alanine and oxaloacetate - no; Homocysteine plus N5-Methyl-THF produces methionine and THF - yes; Homocysteine plus serine produces cystathionine - no; Histidine produces histamine - no

Question 9

Vitamin-B12 deficiency is not seen in which of the following conditions?

Accepted Answer

Resection of jejunum

Answer

Resection of ileum

Answer

Achlorhydria

Answer

Parietal cell destruction

Question 10

Which vitamin is essential for the metabolism of sulfur-containing amino acids?

Accepted Answer

Folic acid

Answer

Biotin

Answer

Vitamin C

Answer

Thiamine

Vitamins and Coenzymes — MCQs

Vitamins and Coenzymes — MCQs

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