Vitamins and Coenzymes Practice Questions

Q: Which vitamin deficiency is associated with night blindness and impaired immunity?

Vitamin A. ***Vitamin A*** - **Vitamin A deficiency** is a classic cause of **night blindness** (nyctalopia) due to its role in the formation of **rhodopsin**, a light-sensitive pigment in the retina. - It also plays a crucial role in maintaining **immune function**, particularly in the integrity of epithelial tissues and normal lymphocyte activity. *Vitamin K* - **Vitamin K** is primarily involved in **blood clotting** (coagulation) through its role in the synthesis of clotting factors. - Deficiency leads to **bleeding disorders** and has no direct association with night blindness or significant impaired immunity. *Vitamin C* - **Vitamin C** (ascorbic acid) is essential for **collagen synthesis**, acting as an antioxidant and playing a role in immune defense. - Severe deficiency causes **scurvy**, characterized by bleeding gums, poor wound healing, and fatigue, but not night blindness. *Vitamin D* - **Vitamin D** is crucial for **calcium and phosphate metabolism**, bone health, and immune regulation. - Deficiency can lead to **rickets** in children and **osteomalacia** in adults, and while it impacts immunity, it does not cause night blindness.

Q: What is the major source of cyanocobalamin (vitamin B12)?

Animal-only diet. ***Animal-only diet*** - **Cyanocobalamin (vitamin B12)** is primarily found in **animal products** such as meat, fish, poultry, eggs, and dairy. - It is synthesized by microorganisms and accumulates in animal tissues, making animal-derived foods the most reliable dietary source for humans. *Sunlight* - **Sunlight** is the primary source of **vitamin D** synthesis in the skin, not vitamin B12. - Exposure to UV radiation from the sun does not contribute to the production or uptake of cyanocobalamin. *Plant-only diet* - A **plant-only diet (vegan diet)** is deficient in naturally occurring **vitamin B12**, as plants do not synthesize this vitamin. - Vegans often require **fortified foods** or **supplements** to meet their B12 needs. *None of the options* - This option is incorrect because an **animal-only diet** is identified as a major source of cyanocobalamin. - The question has a correct answer among the provided choices.

Q: Most abundant form of pro-vitamin A is:-

Beta carotene. ***Beta carotene*** - **Beta-carotene** is the most widely distributed and abundant form of **provitamin A** in plants. - It yields two molecules of **retinal** upon enzymatic cleavage, which can then be converted to **retinol**. *Retinol* - **Retinol** is the active form of **vitamin A** and is not a pro-vitamin. - It is derived from pro-vitamin A carotenoids or ingested directly as preformed vitamin A. *Alpha-carotene* - **Alpha-carotene** is another form of **provitamin A**, but it is **less abundant** than beta-carotene. - It yields only one molecule of **retinal** because of its asymmetric structure. *Retinaldehyde* - **Retinaldehyde** (retinal) is an intermediate metabolite in the **vitamin A pathway**, converted from provitamin A or retinol. - It is not considered a pro-vitamin but rather a direct precursor to other active forms of vitamin A, such as **retinol** and **retinoic acid**.

Q: 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?

Niacin (Vitamin B3). ***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.

Q: Which coenzyme is required by 6-phosphogluconate dehydrogenase?

NADP. ***Correct NADP*** - **6-phosphogluconate dehydrogenase** is a key enzyme in the **oxidative phase of the pentose phosphate pathway**, which generates **NADPH**. - **NADP+** acts as an electron acceptor, getting reduced to **NADPH**, which is crucial for reductive biosynthesis and **antioxidant defense**. *Incorrect FAD* - **Flavin adenine dinucleotide (FAD)** is a derivative of **riboflavin (vitamin B2)** and is typically involved in reactions transferring two electrons, often found in **dehydrogenases** that form carbon-carbon double bonds. - Enzymes like **succinate dehydrogenase** (in the TCA cycle) utilize **FAD**, which is not the case for 6-phosphogluconate dehydrogenase. *Incorrect FMN* - **Flavin mononucleotide (FMN)**, also derived from **riboflavin**, is primarily found in **flavoproteins** and acts as a prosthetic group in various **redox reactions**. - It is a component of **Complex I (NADH dehydrogenase)** in the electron transport chain, but not involved in the pentose phosphate pathway's 6-phosphogluconate dehydrogenase reaction. *Incorrect NAD* - **Nicotinamide adenine dinucleotide (NAD+)** is a coenzyme primarily involved in catabolic reactions where it accepts electrons and is reduced to **NADH**, typically in glycolysis, the TCA cycle, and fatty acid oxidation. - While structurally similar to NADP+, **NAD+** is involved in ATP production, whereas **NADP+** is used in anabolic processes.

Q: Female, on maize as a staple diet. History of diarrhoea and lesion in the neck region. This is due to deficiency of which of the following?

Niacin. ***Niacin*** * The constellation of **diarrhea**, **dermatitis** (neck lesion, often a "Casal's necklace"), and the exclusive reliance on a **maize staple diet** is highly characteristic of **pellagra**, which is caused by a **niacin (vitamin B3) deficiency**. * Maize contains niacin in a bound form (niacytin) that is largely **unbioavailable** unless treated with alkali (e.g., historical limewater soaking in some cultures). *Pyridoxine* * Deficiency of **pyridoxine (vitamin B6)** can lead to symptoms such as **skin inflammation (seborrheic dermatitis)**, **glossitis**, **cheilosis**, and neurological issues like **peripheral neuropathy** or **seizures**. * It does not typically present with the classic **diarrhea** and **dermatitis** pattern associated with pellagra in the context of a maize-based diet. *Thiamine* * **Thiamine (vitamin B1) deficiency** is associated with **beriberi**, characterized by cardiovascular symptoms (**wet beriberi** with edema and heart failure) or neurological symptoms (**dry beriberi** with neuropathy and muscle wasting). * It does not cause the specific dermatological lesion on the neck or the triad of symptoms (dermatitis, diarrhea, and dementia) seen with niacin deficiency. *Zinc* * **Zinc deficiency** can manifest as **dermatitis (acrodermatitis enteropathica)**, **diarrhea**, **impaired immune function**, and **poor wound healing** or **growth retardation**. * While it can cause skin lesions and diarrhea, the distinct **photosensitive dermatosis** on the neck and the strong association with a maize staple diet specifically point away from zinc deficiency and towards pellagra.

Q: Vitamin B12 is found maximum in:

Animal products. ***Animal products*** - **Vitamin B12**, or cobalamin, is primarily synthesized by bacteria and accumulates in animal tissues, making **meat, fish, poultry, eggs, and dairy** the richest dietary sources. - Humans generally cannot synthesize vitamin B12 and must obtain it from dietary sources, with **animal-derived foods** being the most concentrated and bioavailable forms. *Sunlight* - **Sunlight** is primarily critical for the synthesis of **Vitamin D** in the skin, not Vitamin B12. - Exposure to sunlight has no direct role in the production or absorption of **Vitamin B12**. *Green leafy vegetables* - **Green leafy vegetables** are excellent sources of nutrients like **folate, Vitamin K, and iron**, but they are generally devoid of naturally occurring **Vitamin B12**. - While some fortified plant-based foods may contain Vitamin B12, naturally, these vegetables do not provide it. *Roots and tubers* - **Roots and tubers** like potatoes, carrots, and sweet potatoes are good sources of carbohydrates, fiber, and various vitamins and minerals such as **Vitamin C and potassium**. - They do not contain significant amounts of **Vitamin B12**, as they are plant-based foods.

Q: Which of the following is the rich source of Vitamin B12?

Meat. ***Meat*** - **Vitamin B12** is primarily found in **animal products** because it is synthesized by bacteria in the digestive tracts of animals. - **Meat**, especially red meat and liver, is an excellent source of this vitamin. *Mango* - Mangoes are a good source of **Vitamin C** and **Vitamin A**, but they contain negligible amounts of Vitamin B12. - As a fruit, mangos are a plant-based food and generally **do not contain B12**. *Carrot* - Carrots are rich in **beta-carotene** (a precursor to Vitamin A) and **fiber**, but they are not a source of Vitamin B12. - Being a vegetable, carrots are a **plant-based food** and lack Vitamin B12. *Spinach* - Spinach is known for its high content of **iron**, **folate**, and **Vitamin K**, but it does not contain Vitamin B12. - Like other plant-based foods, spinach **naturally lacks Vitamin B12**.

Q: A person after consuming raw eggs presents with weakness, fatigue & hypoglycemia. Doctor gave him biotin supplements. Which biotin-dependent enzyme's reduced activity is most likely causing hypoglycemia in this patient:

Pyruvate carboxylase. ***Pyruvate carboxylase*** - This enzyme is crucial for **gluconeogenesis**, converting **pyruvate to oxaloacetate**. Biotin deficiency, often caused by consuming **avidin** in raw eggs, impairs its activity, leading to reduced glucose production and **hypoglycemia**. - **Avidin** present in raw egg whites binds irreversibly to biotin, preventing its absorption and utilization, thereby affecting biotin-dependent enzymes. *Glucose 6 phosphatase* - This enzyme is involved in the final step of **gluconeogenesis** and **glycogenolysis**, releasing free glucose into the bloodstream. While its dysfunction can cause hypoglycemia, it is **not a biotin-dependent enzyme**. - Deficiencies in this enzyme are typically associated with **Von Gierke disease** (glycogen storage disease type I), which has distinct clinical features and is not related to raw egg consumption. *Glycogen phosphorylase* - This enzyme is responsible for the breakdown of **glycogen into glucose-1-phosphate** (**glycogenolysis**). Its inhibition would impair glycogen breakdown and could lead to hypoglycemia, but it is **not biotin-dependent**. - Deficiencies often present as **McArdle disease** (glycogen storage disease type V), characterized by exercise intolerance and muscle pain, which is not the primary presentation here. *Phosphoenol pyruvate carboxykinase* - This enzyme functions in **gluconeogenesis**, converting **oxaloacetate to phosphoenolpyruvate**. While essential for glucose production, it is **not a biotin-dependent enzyme**. - Its activity is regulated by hormones like glucagon and insulin, and its deficiency would impair gluconeogenesis, but the specific link to raw egg consumption and biotin is absent.

Question 1

Which vitamin deficiency is associated with night blindness and impaired immunity?

Accepted Answer

Vitamin A

Answer

Vitamin K

Answer

Vitamin C

Answer

Vitamin D

Question 2

What is the major source of cyanocobalamin (vitamin B12)?

Accepted Answer

Animal-only diet

Answer

Sunlight

Answer

Plant-only diet

Answer

None of the options

Question 3

Most abundant form of pro-vitamin A is:-

Accepted Answer

Beta carotene

Answer

Retinol

Answer

Alpha-carotene

Answer

Retinaldehyde

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?

Accepted Answer

Niacin (Vitamin B3)

Answer

Thiamine (Vitamin B1)

Answer

Vitamin B6 (Pyridoxine)

Answer

Cobalamin (Vitamin B12)

Question 5

Which coenzyme is required by 6-phosphogluconate dehydrogenase?

Accepted Answer

NADP

Answer

FAD

Answer

FMN

Answer

NAD

Question 6

Female, on maize as a staple diet. History of diarrhoea and lesion in the neck region. This is due to deficiency of which of the following?

Accepted Answer

Niacin

Answer

Pyridoxine

Answer

Thiamine

Answer

Zinc

Question 7

Vitamin B12 is found maximum in:

Accepted Answer

Animal products

Answer

Sunlight

Answer

Green leafy vegetables

Answer

Roots and tubers

Question 8

True statement about vitamin K is?

Accepted Answer

Vitamin K affects bone health by activating proteins that bind calcium

Answer

Vitamin K is needed for action of clotting factor 8

Answer

Vitamin K deficiency leads to DVT

Answer

Vitamin K is water soluble

Question 9

Which of the following is the rich source of Vitamin B12?

Accepted Answer

Meat

Answer

Mango

Answer

Carrot

Answer

Spinach

Question 10

A person after consuming raw eggs presents with weakness, fatigue & hypoglycemia. Doctor gave him biotin supplements. Which biotin-dependent enzyme's reduced activity is most likely causing hypoglycemia in this patient:

Accepted Answer

Pyruvate carboxylase

Answer

Glucose 6 phosphatase

Answer

Glycogen phosphorylase

Answer

Phosphoenol pyruvate carboxykinase

Vitamins and Coenzymes — MCQs

Vitamins and Coenzymes — MCQs

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