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 Question:
The question asks us to identify the correct physiological statement regarding the differences between red and white skeletal muscle fibers in terms of their metabolism and organelle composition.

Step 2 : Key Formulas and Approach:
The approach involves comparing the structural and metabolic characteristics of slow-twitch (red) and fast-twitch (white) muscle fibers.
We will evaluate each option based on established muscular physiology.

Step 3 : Detailed Explanation:

• Red Muscle Fibers (Type I): These fibers contain high amounts of myoglobin (an oxygen-storing pigment, which gives them their red color) and a dense network of blood capillaries.
They also contain a very high number of mitochondria, enabling them to utilize oxygen efficiently to produce ATP through aerobic respiration under normal conditions. This statement is correct.

• White Muscle Fibers (Type II): These fibers contain far less myoglobin and fewer mitochondria than red fibers. Thus, statement (B) is incorrect.

• Lactic Acid Accumulation: Since white muscle fibers rely heavily on anaerobic glycolysis for rapid energy, they generate and accumulate lactic acid much faster than red fibers, which primarily perform aerobic respiration. Thus, statement (C) is incorrect.

• Generalization: Not all muscle fibers produce ATP anaerobically; red muscle fibers are highly specialized for aerobic ATP production. Thus, statement (D) is incorrect.

Step 4 : Final Answer:
Therefore, the only correct statement is Option (A).