Which fuel substrates are primarily used to produce ATP by oxidative phosphorylation in skeletal muscle fibers?

• A. Glycogen and creatine phosphate
• B. Lactate and pyruvate
• C. Glucose and fatty acids
• D. Amino acids and nucleotides

Answer: (C)

Verified step by step guidance

1. Understand that ATP production in skeletal muscle fibers occurs through oxidative phosphorylation, a process that takes place in the mitochondria and requires oxygen.
2. Recognize that oxidative phosphorylation primarily uses substrates that can be oxidized to produce energy. These substrates are typically carbohydrates and fats.
3. Identify that glucose, a carbohydrate, is a primary substrate for ATP production. It undergoes glycolysis to form pyruvate, which enters the mitochondria for further oxidation.
4. Acknowledge that fatty acids are another major substrate. They undergo beta-oxidation in the mitochondria to produce acetyl-CoA, which enters the citric acid cycle, leading to ATP production.
5. Conclude that glucose and fatty acids are the primary fuel substrates used in oxidative phosphorylation in skeletal muscle fibers, as they provide the necessary acetyl-CoA for the citric acid cycle and subsequent ATP production.