What is the role of myoglobin in muscle cells?

Myoglobin plays a crucial role in muscle cells by storing oxygen. It is a protein found in the cytoplasm of muscle cells and has a high affinity for oxygen, allowing it to bind oxygen molecules. This stored oxygen is essential for aerobic respiration, especially during periods of intense exercise when muscles require more oxygen to produce the energy needed for sustained contractions. By having an abundant supply of myoglobin, muscle cells can efficiently manage their oxygen levels, ensuring that they continue to function effectively during physical activity.

The other choices do not reflect the true function of myoglobin. While energy for muscle contractions is generated primarily through adenosine triphosphate (ATP), and nutrients are delivered by the circulatory system rather than being stored within muscle cells, muscle repair processes are more related to other factors such as satellite cells and growth factors. Thus, "stores oxygen" accurately captures the pivotal role myoglobin plays in supporting muscle metabolism and performance.