Vitamin C and Collagen Synthesis Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Vitamin C and Collagen Synthesis. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Vitamin C and Collagen Synthesis Indian Medical PG Question 1: The main function of Vitamin C in the body is
- A. Cofactor for hydroxylation reactions in collagen synthesis (Correct Answer)
- B. Regulation of lipid synthesis
- C. Involvement as antioxidant
- D. Inhibition of cell growth
Vitamin C and Collagen Synthesis Explanation: ***Cofactor for hydroxylation reactions in collagen synthesis***
- Vitamin C (ascorbic acid) serves as an essential **cofactor** for **prolyl hydroxylase** and **lysyl hydroxylase** enzymes.
- These enzymes catalyze the **hydroxylation of proline and lysine** residues in collagen, forming **hydroxyproline** and **hydroxylysine**.
- This hydroxylation is crucial for the **stability and cross-linking** of collagen triple helix structure.
- Deficiency leads to **scurvy**, characterized by defective collagen synthesis, bleeding gums, poor wound healing, and bone abnormalities.
- This is the **primary and main function** of Vitamin C in the human body.
*Involvement as antioxidant*
- While Vitamin C does act as a **water-soluble antioxidant**, protecting cells from oxidative damage by free radicals, this is a **secondary function**.
- It can donate electrons to neutralize reactive oxygen species and regenerate other antioxidants like Vitamin E.
- This protective role is important but not the main function compared to its role in collagen synthesis.
*Regulation of lipid synthesis*
- Vitamin C is **not directly involved** in the primary pathways of lipid synthesis or metabolism.
- It may play a minor role in **carnitine synthesis** (needed for fatty acid oxidation), but this is not a major function.
- Other nutrients like B vitamins play more significant roles in lipid metabolism regulation.
*Inhibition of cell growth*
- Vitamin C does **not inhibit normal cell growth**; it is essential for cell health, differentiation, and tissue repair.
- While high doses may have some anti-proliferative effects in certain cancer cell lines in vitro, this is not a physiological function in the healthy body.
Vitamin C and Collagen Synthesis Indian Medical PG Question 2: A patient presenting with bleeding gums and easy bruisability was diagnosed with scurvy. This condition results from a deficiency of which of the following?
- A. Inhibition of vitamin K
- B. Increased collagen breakdown
- C. Defective collagen synthesis
- D. Low vitamin C (Correct Answer)
Vitamin C and Collagen Synthesis Explanation: ***Low vitamin C***
- **Scurvy** is directly caused by a severe deficiency of **vitamin C (ascorbic acid)**.
- Vitamin C is a cofactor for **prolyl hydroxylase** and **lysyl hydroxylase**, enzymes essential for **collagen synthesis**.
- Its deficiency leads to defective collagen formation, resulting in weakened connective tissues and fragile capillaries, explaining the bleeding gums and easy bruising.
*Inhibition of vitamin K*
- **Vitamin K** is crucial for the synthesis of **blood clotting factors** (II, VII, IX, X).
- Its inhibition (e.g., by warfarin) would lead to bleeding disorders but does not explain the characteristic connective tissue problems (poor wound healing, perifollicular hemorrhages) seen in scurvy.
*Increased collagen breakdown*
- Conditions like **Ehlers-Danlos syndrome** involve abnormal collagen structure leading to tissue fragility.
- Scurvy is characterized by a problem in the *synthesis* rather than the increased *breakdown* of collagen.
*Defective collagen synthesis*
- While this describes the **pathophysiological mechanism** of scurvy, it is not the answer to what the patient is *deficient in*.
- The question asks for the underlying **nutritional deficiency**, which is **vitamin C**—the root cause that leads to defective collagen synthesis.
Vitamin C and Collagen Synthesis Indian Medical PG Question 3: How does vitamin C deficiency lead to scurvy?
- A. Defective collagen formation due to impaired synthesis (Correct Answer)
- B. Impaired immune response due to vitamin deficiencies
- C. Iron deficiency anemia
- D. Malabsorption of fat-soluble vitamins
Vitamin C and Collagen Synthesis Explanation: ***Defective collagen formation due to impaired synthesis***
- **Vitamin C** is a crucial cofactor for **prolyl hydroxylase** and **lysyl hydroxylase**, enzymes essential for the hydroxylation of proline and lysine residues in collagen.
- Without proper hydroxylation, collagen molecules cannot form stable **triple helix structures**, leading to weakened connective tissues throughout the body, manifesting as scurvy.
*Impaired immune response due to vitamin deficiencies*
- While various vitamin deficiencies can impair the immune response, **scurvy's primary pathology** stems from defective collagen synthesis, not directly from immune system dysfunction.
- Immune compromise might be a secondary effect in severe, prolonged scurvy, but it's not the **direct cause of the characteristic symptoms** like bleeding gums and poor wound healing.
*Iron deficiency anemia*
- **Vitamin C does enhance iron absorption** in the gut, so severe deficiency can indirectly contribute to **iron deficiency anemia**.
- However, iron deficiency anemia is a *consequence* of prolonged scurvy, not the primary mechanism by which scurvy's defining symptoms occur.
*Malabsorption of fat-soluble vitamins*
- **Vitamin C** is a water-soluble vitamin and its deficiency does not directly cause malabsorption of **fat-soluble vitamins** (A, D, E, K).
- Malabsorption of fat-soluble vitamins is typically linked to disorders of fat digestion or absorption, such as **pancreatic insufficiency** or **celiac disease**.
Vitamin C and Collagen Synthesis Indian Medical PG Question 4: Defect in Menkes disease:
- A. ATP7A (Copper-transporting ATPase) (Correct Answer)
- B. Prolyl oxidase
- C. Prolyl hydroxylase
- D. Lysyl oxidase
Vitamin C and Collagen Synthesis Explanation: ***ATP7A (Copper-transporting ATPase)***
- **Menkes disease** is an X-linked recessive disorder characterized by a defect in the **ATP7A gene**, which encodes a copper-transporting ATPase.
- This defect leads to impaired intestinal absorption and cellular transport of copper, resulting in **copper deficiency** in various tissues despite adequate dietary intake.
*Prolyl oxidase*
- **Prolyl oxidase** is involved in proline metabolism, and defects are not associated with Menkes disease.
- Deficiency of this enzyme is usually linked to hyperprolinemia.
*Prolyl hydroxylase*
- **Prolyl hydroxylase** is an enzyme critical for the hydroxylation of proline residues in collagen, a step essential for collagen stability.
- While collagen synthesis requires copper (for lysyl oxidase), a direct defect in prolyl hydroxylase is not the cause of Menkes disease.
*Lysyl oxidase*
- **Lysyl oxidase** is a copper-dependent enzyme required for the cross-linking of collagen and elastin, contributing to connective tissue strength.
- Although lysyl oxidase activity is reduced in Menkes disease due to copper deficiency, the primary defect is in the **ATP7A transporter**, not the lysyl oxidase enzyme itself.
Vitamin C and Collagen Synthesis Indian Medical PG Question 5: Maximum concentration of vitamin A is found in which organ?
- A. Liver (Correct Answer)
- B. Kidney
- C. Lung
- D. Heart
Vitamin C and Collagen Synthesis Explanation: ***Liver***
- The **liver** is the primary organ for **storage of vitamin A** (retinyl esters), accounting for 90% of the body's total vitamin A content.
- **Hepatic stellate cells** within the liver are specialized for storing the majority of this fat-soluble vitamin.
*Kidney*
- The **kidney** plays a role in **vitamin D metabolism** and excretion, but not significant vitamin A storage.
- While it helps regulate blood levels of various substances, it does not accumulate large quantities of vitamin A.
*Lung*
- The **lung** does not serve as a major storage site for **vitamin A**.
- Its primary functions are related to **gas exchange**, not nutrient storage.
*Heart*
- The **heart** is responsible for **pumping blood** throughout the body and has minimal involvement in vitamin A storage.
- It utilizes certain vitamins for its metabolic processes but does not act as a primary reservoir.
Vitamin C and Collagen Synthesis Indian Medical PG Question 6: Which of the following is not typically associated with osteogenesis imperfecta?
- A. Blue sclera
- B. Lax ligament
- C. Bilateral Hip dislocation (Correct Answer)
- D. Osteoporosis
Vitamin C and Collagen Synthesis Explanation: ***Bilateral Hip dislocation***
- While hip dislocations can occur in severe cases due to bone fragility, **bilateral hip dislocation** is not a characteristic or typical primary association with osteogenesis imperfecta.
- The underlying issue is primarily **bone fragility** leading to fractures, not inherent joint instability or malformation causing bilateral dislocation.
*Blue sclera*
- **Blue sclera** is a classic sign of osteogenesis imperfecta, caused by the thinness of the sclera allowing the underlying choroid vessels to show through.
- This is due to a defect in **Type I collagen** synthesis, which affects not only bones but also other connective tissues including the sclera.
*Lax ligament*
- **Lax ligaments** are common in osteogenesis imperfecta due to the generalized **connective tissue defect**, particularly involving Type I collagen.
- This can contribute to joint instability, *hypermobility*, and an increased risk of sprains.
*Osteoporosis*
- **Osteoporosis** with reduced bone mineral density is a hallmark feature of osteogenesis imperfecta, leading to **fragile bones** and recurrent fractures.
- The genetic defect in **Type I collagen** impairs bone matrix formation, resulting in weak and brittle bones.
Vitamin C and Collagen Synthesis Indian Medical PG Question 7: Prolyl hydroxylase requires which cofactor?
- A. Vitamin C (Correct Answer)
- B. Iron (Fe²⁺)
- C. Molybdenum
- D. Vitamin K1
Vitamin C and Collagen Synthesis Explanation: ***Vitamin C***
- **Prolyl hydroxylase** is an enzyme critical for the hydroxylation of proline residues during **collagen synthesis**.
- **Vitamin C** (ascorbic acid) acts as an essential **cofactor**, reducing the ferric iron of the enzyme back to its ferrous state after each catalytic cycle, enabling continued activity.
- The enzyme requires both **iron (Fe²⁺)** as a metal cofactor and **vitamin C** to maintain the iron in its reduced state.
*Iron (Fe²⁺)*
- While **iron** is indeed required by prolyl hydroxylase as a **metal cofactor**, the question asks for the cofactor, which specifically refers to **vitamin C**.
- Iron functions as part of the enzyme's active site, but vitamin C is the reducing agent that keeps iron functional.
- Vitamin C deficiency (scurvy) leads to defective collagen synthesis despite adequate iron.
*Molybdenum*
- **Molybdenum** is a cofactor for several human enzymes, including **xanthine oxidase** and **sulfite oxidase**.
- However, it plays no direct role in the activity of prolyl hydroxylase.
*Vitamin K1*
- **Vitamin K1** is a crucial cofactor for **gamma-glutamyl carboxylase**, an enzyme involved in the carboxylation of glutamic acid residues in clotting factors.
- It is not involved in the hydroxylation of proline by prolyl hydroxylase.
Vitamin C and Collagen Synthesis Indian Medical PG Question 8: A patient presents with annular, scaly plaques with perifollicular extension on the trunk. What is the most likely diagnosis?
- A. Psoriasis
- B. Lichen planus
- C. Tinea (Correct Answer)
- D. Pityriasis versicolor
Vitamin C and Collagen Synthesis Explanation: ***Tinea***
- **Tinea corporis** classically presents with **annular, scaly plaques with central clearing** and an active, raised border.
- On hairy areas or with follicular involvement, dermatophyte infections show **perifollicular extension** as the fungus invades hair follicles.
- The **annular morphology with scale** is pathognomonic for dermatophyte infection, confirmed by **KOH preparation** showing septate hyphae.
- Common sites include trunk, limbs, and any body area with hair follicles.
*Psoriasis*
- Presents with **well-demarcated, erythematous plaques** with **silvery-white scales**, typically on extensor surfaces (elbows, knees, scalp).
- **Follicular psoriasis** is rare and shows **pinpoint follicular papules**, not annular plaques with perifollicular extension.
- Auspitz sign (pinpoint bleeding on scale removal) helps differentiate from tinea.
*Lichen planus*
- Characterized by **pruritic, polygonal, purple, planar papules** (the "6 Ps").
- **Lichen planopilaris** (follicular variant) causes **scarring alopecia** with follicular hyperkeratosis, not annular scaly plaques.
- Wickham striae may be visible on mucosal surfaces.
*Pityriasis versicolor*
- Caused by **Malassezia species**, presents as **hypo- or hyperpigmented macules** with fine scale on trunk and upper arms.
- **Follicular variant** (pityriasis folliculorum) shows discrete follicular papules, NOT annular plaques.
- "Spaghetti and meatballs" appearance on KOH prep (short hyphae and spores) differentiates from dermatophytes.
Vitamin C and Collagen Synthesis Indian Medical PG Question 9: Which of the following is absolutely essential for wound healing?
- A. Balanced diet
- B. Vitamin C (Correct Answer)
- C. Vitamin D
- D. Carbohydrates
Vitamin C and Collagen Synthesis Explanation: ***Vit C***
- **Vitamin C** is absolutely essential for wound healing because it is a crucial cofactor for **collagen synthesis**, specifically for the hydroxylation of proline and lysine residues.
- Without adequate vitamin C, strong, stable **collagen fibers** cannot be formed, leading to impaired wound tensile strength and delayed healing.
*Balanced diet*
- While a **balanced diet** provides overall nutritional support for wound healing, it is a general principle, not a single, absolutely essential nutrient in the same way **Vitamin C** is for a specific biochemical process.
- A balanced diet incorporates many components, but specifically points to **Vitamin C's** role makes it more specific and thereby the correct answer.
*Vit D*
- **Vitamin D** plays a role in bone health and immune function but is not directly involved in the **collagen synthesis** or immediate structural integrity of new tissue formation in wound healing to the same critical extent as Vitamin C.
- Its effects on wound healing are more indirect, through modulation of inflammation and cell proliferation, rather than being an "absolutely essential" direct component of the healing process.
*Carbohydrates*
- **Carbohydrates** are important for providing energy for cellular activities during wound healing.
- However, they are not directly involved in the **structural integrity** or **collagen formation** of the healing tissue itself, unlike Vitamin C.
Vitamin C and Collagen Synthesis Indian Medical PG Question 10: Which nutrient deficiency directly impairs hydroxylation during collagen synthesis?
- A. A. Vitamin D
- B. B. Copper
- C. C. Vitamin E
- D. D. Vitamin C (Correct Answer)
Vitamin C and Collagen Synthesis Explanation: ***Vitamin C***
- **Vitamin C** (ascorbic acid) is a crucial **cofactor** for the enzymes **prolyl hydroxylase** and **lysyl hydroxylase**, which are essential for **collagen cross-linking and stability**.
- Its deficiency leads to **scurvy**, characterized by weakened connective tissue, impaired wound healing, and fragile blood vessels due to **defective collagen synthesis**.
*Vitamin D*
- **Vitamin D** is primarily involved in **calcium and phosphate homeostasis**, which are vital for bone mineralization.
- Its deficiency can lead to **rickets** in children and **osteomalacia** in adults, conditions of weakened bones, but not directly to collagen defects.
*Copper*
- **Copper** is a cofactor for **lysyl oxidase**, an enzyme that cross-links collagen and elastin, contributing to the tensile strength of connective tissues.
- While copper deficiency can affect collagen structure, **Vitamin C deficiency** has a more direct and severe impact on the initial synthesis and hydroxylation steps of collagen, making it the primary answer for collagen defects.
*Vitamin E*
- **Vitamin E** is a fat-soluble antioxidant that protects cell membranes from **oxidative damage**.
- Its deficiency is associated with neurological symptoms and hemolytic anemia but does not directly cause defects in **collagen synthesis or structure**.
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