Energy sources available to form ATP in muscle fibers are below. Which statement is correct?
1. phosphorylation of ADP by creatine phosphate
2. oxidative phosphorylation of ADP in the mitochondria
3. phosphorylation of ADP by the glycolytic pathway in the cytosol

Question

Energy sources available to form ATP in muscle fibers are below. Which statement is correct? 
1.	phosphorylation of ADP by creatine phosphate
2.	oxidative phosphorylation of ADP in the mitochondria
3.	phosphorylation of ADP by the glycolytic pathway in the cytosol

Quizplus · Accepted Answer

Creatine phosphate is the first source of ATP utilized during the initial phase of contraction, because it can provide ATP more quickly than oxidative phosphorylation and the glycolytic pathway. However, it only provides a small amount of ATP and is quickly depleted, so oxidative phosphorylation and glycolysis take over to supply ATP for prolonged contractions. Option A is incorrect because oxidative phosphorylation produces more ATP than creatine phosphate. Option C is incorrect because only oxidative phosphorylation is considered aerobic, while creatine phosphate and glycolysis are anaerobic. Option D is incorrect because creatine phosphate is used in the cytosol and not in the mitochondria. Option E is incorrect as there is a correct answer.

Energy Sources Available to Form ATP in Muscle Fibers Are