Final answer:
The statement is true; creatine phosphate serves as an immediate energy reserve to quickly generate ATP, necessary for the first few seconds of a muscle contraction.
Step-by-step explanation:
The energy source for the conversion of ADP to ATP in an actively contracting muscle is creatine phosphate. This statement is true.
Creatine phosphate is a high-energy compound in muscle cells that stores energy in its phosphate bonds, which can be mobilized to quickly regenerate ATP from ADP during the initial phase of muscle contraction. The enzyme creatine kinase catalyzes this reaction, making ATP available for muscle contractions at the very beginning, which is vital because the existing ATP reserves in muscles are sufficient only for a few seconds of contraction. This mechanism is a rapid way to produce ATP, allowing muscles to contract forcefully almost immediately.
While the ATP generated by creatine phosphate can fuel muscles for only about 15 seconds, it is crucial for short bursts of high-intensity activity, after which the muscles must use other pathways, like glycolysis or aerobic respiration, to continue producing ATP for muscle contraction.