Vitamins and Coenzymes Practice Questions

Q: Which of the following vitamin deficiencies is found in patients with gastric cancer?

Vitamin B12. **Explanation:** The correct answer is **Vitamin B12**. **Why Vitamin B12 is the correct answer:** Gastric cancer often involves the destruction or surgical resection of the gastric mucosa, specifically the **parietal cells** located in the body and fundus of the stomach. These cells are responsible for secreting **Intrinsic Factor (IF)**. Vitamin B12 (cobalamin) requires IF to form a complex that survives the acidic environment of the stomach and allows for absorption in the **terminal ileum**. In gastric cancer, the loss of parietal cells leads to IF deficiency, resulting in secondary Vitamin B12 malabsorption and potentially megaloblastic anemia (pernicious-like state). Additionally, the achlorhydria (lack of HCl) associated with gastric atrophy prevents the release of B12 from dietary proteins. **Why the other options are incorrect:** * **Vitamin C:** While low levels are associated with an increased *risk* of developing gastric cancer due to reduced antioxidant protection, the cancer itself does not characteristically cause a deficiency through a specific physiological mechanism like B12. * **Vitamin A & D:** These are fat-soluble vitamins. Their deficiency is typically associated with fat malabsorption syndromes (e.g., pancreatic insufficiency, biliary obstruction, or celiac disease) rather than the specific loss of gastric intrinsic factor. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Absorption:** Vitamin B12 is absorbed in the **terminal ileum**, while Iron is absorbed in the **duodenum**. * **Post-Gastrectomy:** Patients undergoing total gastrectomy for gastric cancer *must* receive lifelong parenteral Vitamin B12 supplementation. * **Schilling Test:** Historically used to differentiate between causes of B12 deficiency (though largely replaced by antibody testing and metabolite levels). * **Associated Finding:** Look for **hypersegmented neutrophils** on a peripheral smear in patients with B12 deficiency.

Q: Which vitamin is given in type 2B familial hyperlipidemia?

Nicotinic acid. **Explanation:** **Nicotinic acid (Vitamin B3/Niacin)** is the correct answer because it is a potent lipid-lowering agent. In **Type 2B Familial Hyperlipidemia** (characterized by elevated LDL and VLDL), Niacin acts by inhibiting the enzyme **hormone-sensitive lipase** in adipose tissue. This reduces the flow of free fatty acids to the liver, thereby decreasing the synthesis of VLDL and its metabolic product, LDL. Additionally, Niacin is the most effective agent for increasing HDL levels by reducing its clearance. **Analysis of Incorrect Options:** * **A. Thiamine (B1):** Functions as a coenzyme (TPP) for oxidative decarboxylation reactions (e.g., Pyruvate Dehydrogenase). It has no role in lipid lowering. * **B. Riboflavin (B2):** Precursor for FMN and FAD, involved in redox reactions. It does not affect plasma lipid profiles. * **D. Pantothenic acid (B5):** A component of Coenzyme A (CoA). While CoA is essential for fatty acid metabolism, pharmacological doses of B5 are not used to treat hyperlipidemia. **High-Yield Clinical Pearls for NEET-PG:** * **Side Effects:** The most common side effect of Niacin is **cutaneous flushing**, mediated by Prostaglandin $D_2$ and $E_2$. This can be prevented by pre-treatment with **Aspirin**. * **Metabolic Risks:** Niacin can cause **hyperuricemia** (precipitating gout) and **hyperglycemia** (impaired glucose tolerance). * **Deficiency:** Deficiency leads to **Pellagra** (3 Ds: Dermatitis, Diarrhea, Dementia). * **Synthesis:** It can be synthesized in the body from the amino acid **Tryptophan** (60 mg Tryptophan = 1 mg Niacin).

Q: Vitamin K dependent clotting factors include all EXCEPT?

Factor VIII. **Explanation:** The correct answer is **Factor VIII** because it is not dependent on Vitamin K for its synthesis or function. Vitamin K acts as a vital cofactor for the enzyme **$\gamma$-glutamyl carboxylase**, which adds a carboxyl group to glutamate residues on specific clotting factors. This post-translational modification allows these factors to bind calcium ions ($Ca^{2+}$) and attach to phospholipid membranes, a crucial step in the coagulation cascade. **Breakdown of Options:** * **Factor VIII (Option B):** This is a glycoprotein synthesized primarily in the sinusoidal endothelial cells of the liver and extrahepatic sites. It functions as a cofactor for Factor IXa in the intrinsic pathway. It does not undergo $\gamma$-carboxylation and is therefore **not** Vitamin K dependent. * **Factor VII (Option A):** A Vitamin K-dependent serine protease that initiates the extrinsic pathway. It has the shortest half-life among all clotting factors. * **Prothrombin / Factor II (Option C):** A Vitamin K-dependent zymogen that is converted to thrombin. * **Factor IX (Option D):** A Vitamin K-dependent factor involved in the intrinsic pathway. **High-Yield NEET-PG Pearls:** 1. **Mnemonic:** Remember the Vitamin K-dependent factors as **"1972"** (Factors **10, 9, 7, and 2**) plus **Protein C and Protein S**. 2. **Warfarin Mechanism:** Warfarin inhibits **Vitamin K Epoxide Reductase (VKOR)**, preventing the recycling of Vitamin K and thus inhibiting the $\gamma$-carboxylation of these factors. 3. **Clinical Correlation:** In Vitamin K deficiency or Warfarin overdose, the **Prothrombin Time (PT)** is prolonged first due to the short half-life of Factor VII.

Q: A patient who has undergone partial gastrectomy presents with neurological symptoms. What is the most probable diagnosis?

Vitamin B12 deficiency. **Explanation:** **Why Vitamin B12 deficiency is the correct answer:** Vitamin B12 (Cobalamin) absorption is a complex process requiring **Intrinsic Factor (IF)**, which is secreted by the **parietal cells** of the gastric fundus and body. A partial gastrectomy reduces the population of these cells, leading to a deficiency of IF. Without IF, Vitamin B12 cannot be absorbed in the terminal ileum. Clinically, B12 deficiency is unique because it causes **Subacute Combined Degeneration of the Spinal Cord (SCD)**, involving the posterior columns (loss of vibration/proprioception) and lateral corticospinal tracts (spasticity). This explains the "neurological symptoms" mentioned in the question, which distinguishes it from other macrocytic anemias. **Why the other options are incorrect:** * **Folic acid deficiency:** While it causes megaloblastic anemia, it **does not** cause neurological symptoms. Furthermore, folate is absorbed in the jejunum and does not require gastric intrinsic factor. * **Thiamine (B1) deficiency:** While it causes neurological issues (Wernicke-Korsakoff), it is typically associated with chronic alcoholism or persistent vomiting, not specifically with the loss of gastric parietal cells. * **Iron deficiency:** This is common after gastrectomy (due to decreased gastric acid/HCl which aids iron absorption), but it presents with microcytic anemia and fatigue, not neurological deficits. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Absorption:** B12 is absorbed in the **Terminal Ileum**; Iron in the **Duodenum**; Folate in the **Jejunum**. * **Schilling Test:** Historically used to differentiate causes of B12 malabsorption. * **Biochemical Marker:** In B12 deficiency, both **Methylmalonic acid (MMA)** and **Homocysteine** levels are elevated. In Folate deficiency, only Homocysteine is elevated. * **Storage:** B12 is the only water-soluble vitamin stored in the liver for significant periods (3–5 years).

Q: A patient with malabsorption who develops a deficiency of vitamin A is most likely to subsequently develop?

Night blindness. **Explanation:** **1. Why Night Blindness is Correct:** Vitamin A (Retinol) is essential for the synthesis of **rhodopsin** (visual purple), a light-sensitive pigment found in the rod cells of the retina. Rods are responsible for vision in low-light conditions (scotopic vision). In Vitamin A deficiency, the regeneration of rhodopsin is impaired, leading to **Nyctalopia** (Night Blindness), which is typically the earliest clinical manifestation of the deficiency. **2. Why the Other Options are Incorrect:** * **Acute Leukemia:** While Vitamin A derivatives (like All-trans retinoic acid) are used to treat Acute Promyelocytic Leukemia (APL), a deficiency of the vitamin does not cause leukemia. * **Intestinal Metaplasia:** Vitamin A deficiency causes **Squamous Metaplasia** of epithelial surfaces (like the respiratory tract or conjunctiva), not intestinal metaplasia. Intestinal metaplasia is usually associated with chronic irritation, such as H. pylori infection in the stomach or Barrett’s esophagus. * **Megaloblastic Anemia:** This is caused by a deficiency of Vitamin B12 (Cobalamin) or Vitamin B9 (Folic acid), which are required for DNA synthesis. Vitamin A is not involved in erythropoiesis in this manner. **3. Clinical Pearls for NEET-PG:** * **Earliest Symptom:** Night Blindness (Nyctalopia). * **Earliest Sign:** Conjunctival Xerosis (dryness). * **Pathognomonic Sign:** **Bitot’s Spots** (triangular, foamy patches on the bulbar conjunctiva). * **Keratomalacia:** Softening of the cornea; it is a medical emergency representing advanced deficiency. * **WHO Classification:** Vitamin A deficiency is classified under the **WHO Xerophthalmia classification** (X1A to X3B). * **Storage:** Vitamin A is stored in the liver in **Ito cells** (Stellate cells).

Q: Which of the following is not involved in energy metabolism?

Vitamin B12. **Explanation:** The correct answer is **Vitamin B12 (Cobalamin)**. While Vitamin B12 is essential for DNA synthesis and neurological function, it is not a direct co-factor in the primary energy-producing pathways (Glycolysis, TCA cycle, and Electron Transport Chain) in the same way that B1, B3, and B7 are. **Why Vitamin B12 is the correct answer:** Vitamin B12 primarily acts as a co-factor for two enzymes: **Methionine synthase** (homocysteine to methionine) and **Methylmalonyl-CoA mutase** (propionate metabolism). Although it helps process certain fatty acids and amino acids into the TCA cycle, it is not considered a core "energy metabolism" vitamin compared to the others listed, which are ubiquitous in carbohydrate and fat oxidation. **Why the other options are incorrect:** * **Vitamin B1 (Thiamine):** As Thiamine Pyrophosphate (TPP), it is a vital co-factor for **Pyruvate Dehydrogenase** and **alpha-ketoglutarate dehydrogenase**, making it central to carbohydrate metabolism and the TCA cycle. * **Vitamin B3 (Niacin):** It forms **NAD+ and NADP+**, the primary electron carriers in Glycolysis, the TCA cycle, and the Electron Transport Chain (ETC). * **Vitamin B7 (Biotin):** It acts as a co-factor for **carboxylation reactions**, such as Pyruvate Carboxylase (gluconeogenesis) and Acetyl-CoA Carboxylase (fatty acid synthesis), which are fundamental to energy homeostasis. **NEET-PG High-Yield Pearls:** * **The "Energy Vitamins":** B1, B2, B3, B5, and B7 are directly involved in the release of energy from macronutrients. * **B12 Deficiency:** Leads to **Megaloblastic Anemia** (due to folate trap) and **Subacute Combined Degeneration** of the spinal cord (due to methylmalonyl-CoA accumulation). * **Key Enzyme:** Remember that B12 is required to convert Methylmalonyl-CoA to Succinyl-CoA; a deficiency leads to elevated **Methylmalonic acid (MMA)** levels.

Q: Following resection of the terminal ileum, deficiency of which of the following vitamins is commonly observed along with steatorrhea?

Vitamin B12. **Explanation:** The **terminal ileum** is the specific anatomical site for the absorption of the **Vitamin B12-Intrinsic Factor (IF) complex** and **bile salts**. 1. **Vitamin B12 Absorption:** Dietary B12 binds to Intrinsic Factor (secreted by gastric parietal cells) in the duodenum. This complex travels to the terminal ileum, where specific receptors (cubilin) facilitate its uptake. Resection of this segment leads to megaloblastic anemia and neurological symptoms. 2. **Steatorrhea Connection:** The terminal ileum is also responsible for the reabsorption of conjugated bile salts (enterohepatic circulation). When the ileum is resected, bile salts are lost in the feces. The resulting depletion of the bile salt pool impairs the micellar solubilization of dietary fats, leading to fat malabsorption (**steatorrhea**) and deficiency of fat-soluble vitamins (A, D, E, K). **Analysis of Incorrect Options:** * **Vitamin B9 (Folate):** Primarily absorbed in the **jejunum**. While B12 deficiency can cause a "folate trap," the primary site of folate absorption remains intact in ileal resection. * **Vitamin C:** Absorbed in the **proximal small intestine** (duodenum and jejunum) via SVCT1/2 transporters. * **Vitamin B6 (Pyridoxine):** Absorbed mainly in the **jejunum and ileum** via passive diffusion; isolated deficiency is rare in ileal resection compared to B12. **Clinical Pearls for NEET-PG:** * **Schilling Test:** Historically used to diagnose B12 malabsorption (now largely replaced by antibody testing and metabolite levels). * **Bile Acid Diarrhea:** Small ileal resections ( 100 cm) cause steatorrhea (bile salt depletion). * **Vitamin B12 Stores:** Unlike other water-soluble vitamins, the liver stores enough B12 to last **3–5 years**. Symptoms appear only after stores are exhausted.

Q: Fat-soluble vitamins, compared with their water-soluble counterparts, generally have a greater potential toxicity because they are:

Avidly stored by the body. ### Explanation **1. Why the Correct Answer is Right:** The primary reason for the higher toxicity potential of fat-soluble vitamins (A, D, E, and K) is their **pharmacokinetic profile**. Unlike water-soluble vitamins (B-complex and C), which are readily excreted in the urine when intake exceeds requirements, fat-soluble vitamins are absorbed along with dietary lipids and stored in significant quantities in the **liver and adipose tissue**. Because they are not easily excreted, chronic excessive intake leads to accumulation in these storage sites, eventually reaching toxic levels (Hypervitaminosis). **2. Why the Incorrect Options are Wrong:** * **Option A:** Toxicity is not about the *administered dose* but rather the body's ability to handle that dose. Even small, repeated excess doses of Vitamin A can be more toxic than massive doses of Vitamin C. * **Option C:** While fat-soluble vitamins are lipophilic, they do not function by "dissolving" membrane phospholipids. They integrate into membranes or act via nuclear receptors (e.g., Vitamins A and D). * **Option D:** Both water-soluble and fat-soluble vitamins are equally essential for metabolism. For example, Vitamin B1 (Thiamine) is critical for the TCA cycle, yet it has low toxicity because it is rapidly excreted. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vitamin A Toxicity:** Presents with pseudotumor cerebri (increased intracranial pressure), hepatomegaly, and bone pain. It is also highly **teratogenic**. * **Vitamin D Toxicity:** Leads to hypercalcemia, polyuria, and ectopic calcification (e.g., in kidneys). * **The Exception:** **Vitamin B12** (water-soluble) is an outlier; it is stored in the liver for 3–5 years, but unlike fat-soluble vitamins, it still has a very high safety profile. * **Vitamin K:** Among fat-soluble vitamins, Vitamin K is stored in the smallest amounts and is depleted most rapidly.

Question 1

In the treatment of undiagnosed megaloblastic anemia, vitamin B12 and folic acid should be given together because:

Accepted Answer

Folic acid alone causes improvement of anemic symptoms but neurological dysfunction continues.

Answer

Vitamin B12 acts as a cofactor for dihydrofolate reductase.

Answer

Vitamin B12 deficiency may result in methylfolate trap.

Answer

Folic acid is required for conversion of methylmalonyl CoA to succinyl CoA.

Question 2

Which of the following vitamin deficiencies is found in patients with gastric cancer?

Accepted Answer

Vitamin B12

Answer

Vitamin C

Answer

Vitamin A

Answer

Vitamin D

Question 3

Which vitamin is given in type 2B familial hyperlipidemia?

Accepted Answer

Nicotinic acid

Answer

Thiamine

Answer

Riboflavin

Answer

Pantothenic acid

Question 4

Vitamin K dependent clotting factors include all EXCEPT?

Accepted Answer

Factor VIII

Answer

Factor VII

Answer

Prothrombin

Answer

Factor IX

Question 5

A patient who has undergone partial gastrectomy presents with neurological symptoms. What is the most probable diagnosis?

Accepted Answer

Vitamin B12 deficiency

Answer

Folic acid deficiency

Answer

Thiamine deficiency

Answer

Iron deficiency

Question 6

A patient with malabsorption who develops a deficiency of vitamin A is most likely to subsequently develop?

Accepted Answer

Night blindness

Answer

Acute leukemia

Answer

Intestinal metaplasia

Answer

Megaloblastic anemia

Question 7

Which of the following is not involved in energy metabolism?

Accepted Answer

Vitamin B12

Answer

Vitamin B1

Answer

Vitamin B3

Answer

Vitamin B7

Question 8

Following resection of the terminal ileum, deficiency of which of the following vitamins is commonly observed along with steatorrhea?

Accepted Answer

Vitamin B12

Answer

Vitamin B9

Answer

Vitamin C

Answer

Vitamin B6

Question 9

A 30-year-old lady presented with strong labor pains for the last 3 hours and no progress, found to have pelvic deformities leading to cephalopelvic disproportion. The baby was delivered by cesarean section. The woman is likely to have suffered from the deficiency of which vitamin?

Accepted Answer

Vitamin D

Answer

Vitamin B

Answer

Vitamin C

Answer

Vitamin A

Question 10

Fat-soluble vitamins, compared with their water-soluble counterparts, generally have a greater potential toxicity because they are:

Accepted Answer

Avidly stored by the body

Answer

Administered in larger doses

Answer

Capable of dissolving membrane phospholipids

Answer

Involved in more essential metabolic pathways

Vitamins and Coenzymes — MCQs

Vitamins and Coenzymes — MCQs

On this page

Practice by Chapter

Want unlimited practice?