Vitamins and Coenzymes Practice Questions

Q: Symptoms of Huntington's disease mimic which of the following?

Pellagra. **Explanation:** The correct answer is **Pellagra**. **Why Pellagra?** Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder characterized by the expansion of CAG repeats. The clinical hallmark of HD is the **"3 Ds"** of cognitive and behavioral decline: **Dementia, Depression (or behavioral changes), and Dyskinesia (Chorea)**. Pellagra, caused by a deficiency of **Niacin (Vitamin B3)**, is classically characterized by its own "3 Ds": **Dermatitis, Diarrhea, and Dementia**. The neurological manifestations of Pellagra—specifically the progressive dementia, irritability, and psychiatric symptoms—closely mimic the cognitive decline and behavioral disturbances seen in the early to middle stages of Huntington’s disease. **Analysis of Incorrect Options:** * **Beri-Beri (Vitamin B1 deficiency):** Presents as high-output heart failure (Wet Beri-Beri) or peripheral neuropathy (Dry Beri-Beri). While it involves the nervous system, it lacks the specific choreiform movements and progressive cortical dementia typical of HD. * **Kwashiorkor:** A form of severe protein-energy malnutrition characterized by edema, "flaky paint" dermatosis, and fatty liver. It does not present with the neurodegenerative features of HD. * **Korsakoff Psychosis:** Also due to Thiamine (B1) deficiency, it is characterized by anterograde amnesia and **confabulation**. While it involves cognitive impairment, it is distinct from the motor symptoms (chorea) and global dementia of HD. **NEET-PG High-Yield Pearls:** * **Huntington’s Genetics:** CAG repeat expansion on **Chromosome 4** (Huntingtin gene). It shows **Anticipation**, especially via paternal transmission. * **Pathology:** Atrophy of the **Caudate Nucleus** and Putamen (Striatum), leading to "boxcar ventricles" on imaging. * **Biochemical Shift:** Decreased levels of **GABA** and **Acetylcholine** in the basal ganglia, with a relative increase in Dopamine.

Q: Which coagulation factors are deficient in hemorrhagic disease of the newborn?

Factors II, VII, IX, X. **Explanation:** Hemorrhagic Disease of the Newborn (HDN), now more commonly referred to as **Vitamin K Deficiency Bleeding (VKDB)**, occurs because neonates are born with low stores of Vitamin K. Vitamin K is a critical cofactor for the post-translational carboxylation of specific coagulation factors, rendering them functional. **1. Why Option A is Correct:** Vitamin K is essential for the synthesis of **Factors II (Prothrombin), VII, IX, and X**, as well as proteins C and S. In the absence of Vitamin K, these factors are synthesized in an inactive form (known as PIVKAs—Proteins Induced by Vitamin K Absence). Since newborns have poor placental transfer of Vitamin K, a sterile gut (no bacteria to synthesize Vitamin K), and low levels in breast milk, these four factors are characteristically deficient. **2. Why Other Options are Incorrect:** * **Option B:** Includes Factor III (Tissue Factor), which is a cell surface glycoprotein, not a Vitamin K-dependent clotting factor. * **Option C:** Includes Factor VIII. Factor VIII is part of the intrinsic pathway and is deficient in Hemophilia A, not VKDB. * **Option D:** Includes Factor V. Factor V is a cofactor in the prothrombinase complex but its synthesis is independent of Vitamin K. **Clinical Pearls for NEET-PG:** * **Prophylaxis:** A single IM dose of **1 mg Vitamin K** (Phytonadione) at birth is the standard of care to prevent VKDB. * **Lab Findings:** Characterized by a **prolonged Prothrombin Time (PT)** and often a prolonged aPTT. Platelet count and Fibrinogen levels remain normal. * **Types of VKDB:** * *Early:* Within 24 hours (usually due to maternal drugs like anticonvulsants). * *Classic:* Days 2–7 (due to low intake/breastfeeding). * *Late:* 2 weeks to 6 months (often associated with cholestasis or malabsorption).

Q: A 40-year-old female patient complains of sore gums, loose teeth, and weakness. She also reports delayed wound healing. Laboratory investigations reveal a hemoglobin level of 8 gm%. This patient may be suffering from a deficiency of:

Vitamin C. **Explanation:** The clinical presentation of sore gums, loose teeth, and delayed wound healing is a classic triad for **Scurvy**, which is caused by a deficiency of **Vitamin C (Ascorbic Acid)**. **Why Vitamin C is correct:** Vitamin C is a crucial co-factor for the enzymes **prolyl hydroxylase** and **lysyl hydroxylase**. These enzymes are responsible for the post-translational hydroxylation of proline and lysine residues in collagen. Hydroxyproline is essential for stabilizing the collagen triple helix via hydrogen bonding. In Vitamin C deficiency, defective collagen synthesis leads to: * **Capillary fragility:** Resulting in bleeding gums and petechiae. * **Weakened periodontal ligaments:** Leading to loose teeth. * **Impaired connective tissue repair:** Causing delayed wound healing. * **Anemia:** Vitamin C enhances the absorption of dietary non-heme iron (by reducing $Fe^{3+}$ to $Fe^{2+}$); thus, its deficiency often leads to microcytic anemia. **Why other options are incorrect:** * **Vitamin A:** Deficiency primarily affects vision (night blindness, Xerophthalmia) and epithelial integrity (Bitot’s spots). * **Vitamin B1 (Thiamine):** Deficiency leads to Beriberi (Dry/Wet) or Wernicke-Korsakoff syndrome, characterized by neurological and cardiac symptoms, not collagen defects. * **Vitamin D:** Deficiency causes Rickets in children and Osteomalacia in adults due to impaired calcium and phosphate metabolism. **High-Yield NEET-PG Pearls:** * **Perifollicular hemorrhages** and **"Corkscrew hairs"** are pathognomonic clinical signs of Scurvy. * Vitamin C is the most heat-labile vitamin; it is easily destroyed by cooking. * It acts as a potent antioxidant and is involved in the synthesis of **Catecholamines** (as a cofactor for Dopamine $\beta$-hydroxylase) and **Bile acids**.

Q: Vitamin B12 is mainly absorbed from which part of the gastrointestinal tract?

Ileum. **Explanation:** Vitamin B12 (Cobalamin) absorption is a complex, multi-step process that concludes in the **terminal ileum**. This specific site contains specialized receptors (cubilin) required for the uptake of the B12-Intrinsic Factor complex. **Why Ileum is correct:** After B12 is released from food in the stomach, it binds to R-binders (haptocorrin). In the duodenum, pancreatic proteases digest R-binders, allowing B12 to bind to **Intrinsic Factor (IF)**, secreted by gastric parietal cells. This B12-IF complex travels to the **distal ileum**, where it binds to specific receptors and is absorbed into the portal circulation via transcobalamin II. **Why other options are incorrect:** * **Stomach:** While the stomach is essential for secreting HCl (to release B12 from proteins) and Intrinsic Factor, no significant absorption of the vitamin occurs here. * **Jejunum:** This is the primary site for the absorption of most water-soluble vitamins (like Vitamin C and B-complex) and **Folate**, but it lacks the specific receptors for the B12-IF complex. * **Colon:** The large intestine contains bacteria that synthesize Vitamin B12, but the human body cannot absorb it from this site; it is excreted in the feces. **High-Yield Clinical Pearls for NEET-PG:** * **Schilling Test:** Historically used to determine the cause of B12 deficiency (though largely replaced by antibody testing). * **Pernicious Anemia:** An autoimmune destruction of parietal cells leading to IF deficiency and B12 malabsorption. * **Surgical Correlation:** Patients with ileal resection or Crohn’s disease involving the terminal ileum are at high risk for B12 deficiency and Megaloblastic Anemia. * **Storage:** Unlike other B-vitamins, B12 is stored in the **liver** for 3–5 years; hence, deficiency symptoms take years to manifest.

Q: Antibiotic abuse can induce the deficiency of which of the following vitamins?

Vitamin K. **Explanation:** **Correct Option: C (Vitamin K)** The primary reason for this deficiency is the disruption of the **intestinal microflora**. While Vitamin K1 (Phylloquinone) is obtained from green leafy vegetables, **Vitamin K2 (Menaquinone)** is synthesized by the symbiotic bacteria (such as *E. coli* and *Bacteroides*) residing in the human colon. Prolonged or indiscriminate use of broad-spectrum antibiotics (e.g., cephalosporins, sulfonamides) sterilizes the gut, eliminating these commensal bacteria. This significantly reduces the endogenous production of Vitamin K, leading to a deficiency that manifests as a bleeding tendency due to impaired gamma-carboxylation of clotting factors II, VII, IX, and X. **Why other options are incorrect:** * **A. Thiamine (B1):** Primarily sourced from dietary intake (whole grains, legumes). While some gut synthesis occurs, it is insufficient to meet human requirements; deficiency is usually due to alcoholism or malnutrition. * **B. Niacin (B3):** Primarily derived from the diet or synthesized endogenously from the amino acid **Tryptophan**. It is not significantly dependent on gut flora. * **D. Vitamin E:** A fat-soluble antioxidant obtained strictly from dietary oils and nuts. Its levels are affected by fat malabsorption syndromes, not by gut bacterial colonization. **High-Yield Clinical Pearls for NEET-PG:** * **Newborns** are naturally deficient in Vitamin K because they have a **sterile gut** and breast milk is a poor source. This is why a prophylactic Vitamin K injection is given at birth to prevent Hemorrhagic Disease of the Newborn. * **Warfarin** acts as an antagonist to Vitamin K by inhibiting the enzyme **Vitamin K Epoxide Reductase (VKOR)**. * Always suspect Vitamin K deficiency in a patient on long-term antibiotics who presents with an increased **Prothrombin Time (PT)**.

Question 1

Symptoms of Huntington's disease mimic which of the following?

Accepted Answer

Pellagra

Answer

Beri-Beri

Answer

Kwashiorkor

Answer

Korsakoff psychosis

Question 2

Wernicke's encephalopathy is seen in all the following conditions, EXCEPT:

Accepted Answer

Hypothyroidism

Answer

Chronic alcoholism

Answer

Hyperemesis gravidarum

Answer

Peritoneal dialysis patients

Question 3

The laboratory diagnosis of thiamine deficiency is by:

Accepted Answer

Transketolase assay measured before and after the addition of thiamine pyrophosphate

Answer

Transaldolase assay measured before and after the addition of thiamine pyrophosphate

Answer

Thiamine pyrophosphate assay in RBC after adding sugar

Answer

Serum LDH levels

Question 4

Hangover following alcohol consumption can be treated with which of the following vitamins?

Accepted Answer

Thiamine

Answer

Pyridoxine

Answer

Riboflavin

Answer

Niacin

Question 5

Which coagulation factors are deficient in hemorrhagic disease of the newborn?

Accepted Answer

Factors II, VII, IX, X

Answer

Factors III, VII, IX, X

Answer

Factors II, VIII, IX, X

Answer

Factors II, V, IX, X

Question 6

A 40-year-old female patient complains of sore gums, loose teeth, and weakness. She also reports delayed wound healing. Laboratory investigations reveal a hemoglobin level of 8 gm%. This patient may be suffering from a deficiency of:

Accepted Answer

Vitamin C

Answer

Vitamin A

Answer

Vitamin B1

Answer

Vitamin D

Question 7

Vitamin B12 is mainly absorbed from which part of the gastrointestinal tract?

Accepted Answer

Ileum

Answer

Stomach

Answer

Jejunum

Answer

Colon

Question 8

All of the following statements regarding Vitamin D are true EXCEPT:

Accepted Answer

William's syndrome is characterized by mental retardation, obesity, and precocious puberty

Answer

25-hydroxylation occurs in the liver

Answer

1α-hydroxylation occurs in the kidneys

Answer

In the absence of sunlight, the minimum daily requirement is 400-600 IU

Question 9

Antibiotic abuse can induce the deficiency of which of the following vitamins?

Accepted Answer

Vitamin K

Answer

Thiamine

Answer

Niacin

Answer

Vitamin E

Question 10

Which of the following enzymatic conversions is irreversible?

Accepted Answer

Methylene tetrahydrofolate (THFA) to Methyl tetrahydrofolate (THFA)

Answer

Formyl tetrahydrofolate (THFA) to Methenyl tetrahydrofolate (THFA)

Answer

Methenyl tetrahydrofolate (THFA) to Methylene tetrahydrofolate (THFA)

Answer

All of the above

Vitamins and Coenzymes — MCQs

Vitamins and Coenzymes — MCQs

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