Question

Which one of the following statements is correct?

• A. Red muscle fibres produce ATP aerobically under normal oxygen conditions.
• B. Mitochondria are more in white than in red muscle fibres.
• C. Lactic acid accumulates more in red than in white muscle fibres under similar conditions.
• D. All muscle fibres primarily produce ATP anaerobically.

Hint:

Associate "Red" with "Myoglobin" (which binds oxygen) and "Mitochondria" (which use oxygen).
This setup is designed for aerobic respiration, making red muscles highly resistant to fatigue compared to white muscles.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Skeletal muscle fibers are broadly classified into red muscle fibers (slow-twitch) and white muscle fibers (fast-twitch) based on their myoglobin content, mitochondrial density, and primary metabolic pathways for ATP production.
Step 2: Detailed Explanation:
Let us analyze each statement to determine its correctness:
- Statement (A) is CORRECT: Red muscle fibers contain high amounts of myoglobin (which stores oxygen) and a high density of mitochondria. Under normal oxygen conditions, they efficiently utilize oxygen to produce ATP through aerobic respiration.
- Statement (B) is INCORRECT: Mitochondria are significantly more abundant in red muscle fibers than in white muscle fibers, as red fibers depend heavily on aerobic metabolism.
- Statement (C) is INCORRECT: White muscle fibers have fewer mitochondria and lower myoglobin content. They rely mainly on anaerobic glycolysis for energy, leading to a much faster and greater accumulation of lactic acid compared to red muscle fibers under similar strenuous conditions.
- Statement (D) is INCORRECT: Not all muscle fibers rely primarily on anaerobic metabolism; red muscle fibers are highly specialized for sustained, aerobic ATP production.
Step 3: Final Answer:
The correct statement is: Red muscle fibres produce ATP aerobically under normal oxygen conditions.