Final answer:
Myoglobin is the oxygen-storing molecule found in skeletal muscles of vertebrates, essential for supplying cells with oxygen for aerobic respiration.
Step-by-step explanation:
The molecule found in skeletal muscles of vertebrates that stores oxygen is called myoglobin. Myoglobin is a protein that binds with oxygen to supply cells with this vital element for aerobic respiration. The distinctive red color of muscle tissue is partly due to the presence of myoglobin. It is different from hemoglobin, which is the protein that transports oxygen between the lungs and other tissues. While hemoglobin is found in red blood cells and carries oxygen throughout the body, myoglobin is located within the muscle tissues and is responsible for storing oxygen. This oxygen storage is crucial, especially during intense physical activity when muscles require a rapid supply of oxygen to sustain energy production via aerobic metabolism. It is this stored oxygen that myoglobin provides which is utilized by the muscles.
Contrary to what one might think, myoglobin is not present in higher amounts in fast-twitch fibers but is found in greater quantities in slow-twitch fibers. These slow-twitch fibers are also known as oxidative fibers and are capable of prolonged activity, thanks to the stored oxygen in myoglobin and their abundant mitochondria, where aerobic metabolism occurs.