Final answer:
The correct equation for replenishing ATP in muscle cells is 'Creatine phosphate + ADP > creatine + ATP', where creatine phosphate provides a quick supply of energy by converting ADP back into ATP.option a is correct.
Step-by-step explanation:
The equation that best describes how a muscle cell can replenish ATP when ATP levels are low is A. Creatine phosphate + ADP > creatine + ATP. This process is crucial for the muscle to meet its immediate energy demands, especially during the initial stages of contraction.
When a muscle contracts, it quickly depletes the available ATP. To replenish its ATP supply, the muscle cell uses creatine phosphate as an energy reserve. Creatine phosphate transfers its phosphate group to ADP, thus generating ATP and creatine with the help of the enzyme creatine kinase.
This reaction is very efficient and happens almost instantaneously, allowing for a rapid supply of ATP, fueling muscle contraction for a short duration, typically around 15 seconds.