Final answer:
The statement about skeletal muscle composition is false; skeletal muscle consists of various fiber types and structural proteins, not a simple percentage of MM and MB. Fiber composition varies by muscle use, such as in sprinters or marathon runners, and includes sarcomeres that facilitate contraction.
Step-by-step explanation:
The statement that skeletal muscle is 90% MM and 10% MB is false. Skeletal muscle is a complex tissue composed of muscle fibers, connective tissue, nerve tissue, and blood vessels. The composition of muscle fiber types in skeletal muscle can vary depending on the function and use of the muscle. Professional sprinters, for example, tend to have a higher proportion of fast-twitch fibers (80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers), while professional marathon runners tend to have more slow-twitch fibers (20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers). Furthermore, skeletal muscle tissue consists of bundled muscle fibers that can be broken down into myofibrils, which in turn contain repeating units called sarcomeres. Sarcomeres are not cells but structures within muscle cells made up of actin and myosin proteins responsible for muscle contraction.