Final answer:
Muscles need ATP to contract, and there are three mechanisms for regenerating ATP in active muscles: creatine phosphate, anaerobic glycolysis, and aerobic metabolism. Anaerobic glycolysis is important because it produces ATP quickly, providing energy for short bursts of intense activity. Additionally, muscle cells have a high concentration of mitochondria, which produce ATP through aerobic metabolism to sustain longer muscle contractions.
Step-by-step explanation:
ATP provides the energy for muscle contraction. The three mechanisms for ATP regeneration are creatine phosphate, anaerobic glycolysis, and aerobic metabolism. Creatine phosphate provides about the first 15 seconds of ATP at the beginning of muscle contraction. Anaerobic glycolysis produces small amounts of ATP in the absence of oxygen for a short period. Aerobic metabolism utilizes oxygen to produce much more ATP, allowing a muscle to work for longer periods.
Another advantage of anaerobic respiration is its speed. It produces ATP very quickly. For example, it lets your muscles get the energy they need for short bursts of intense activity.
Note that each thick filament of roughly 300 myosin molecules has multiple myosin heads, and many cross-bridges form and break continuously during muscle contraction. Multiply this by all of the sarcomeres in one myofibril, all the myofibrils in one muscle fiber, and all of the muscle fibers in one skeletal muscle, and you can understand why so much energy (ATP) is needed to keep skeletal muscles working.