Question

match the muscle element with its role in contraction.
z disc sarcomere myosin*
muscle fiber actin
provides anchoring for one of the sliding
filaments
contains protein heads that bind reversibly
to a complementary protein, enabling
siding mechanism
contains active sites to allow reversible
binding of sliding mechanism
basic unit of contraction

Explanation:

• Z - disc: In muscle contraction, the Z - disc serves as an anchoring point for actin filaments. Actin is one of the sliding filaments in the sliding - filament theory of muscle contraction.
• Sarcomere: The sarcomere is the basic unit of muscle contraction. It is the region between two Z - discs and contains the overlapping actin and myosin filaments that interact during contraction.
• Myosin: Myosin is a motor protein. It has protein heads (myosin heads) that can bind reversibly to actin (a complementary protein). The movement of these heads (power stroke) is what drives the sliding of actin filaments over myosin filaments, enabling the sliding mechanism of muscle contraction.
• Actin: Actin filaments contain active sites (specifically, the myosin - binding sites). These sites allow for the reversible binding of myosin heads, which is crucial for the sliding mechanism of muscle contraction.
• Muscle fiber: A muscle fiber is a single muscle cell. It contains many myofibrils, and each myofibril is made up of numerous sarcomeres. So, while not directly related to the specific roles of anchoring, binding for sliding etc. in the same way as the other components in a single - step molecular mechanism sense, it is the larger structural unit that houses the contractile elements (sarcomeres with their actin and myosin). But if we consider the given roles:
• For the role “provides anchoring for one of the sliding filaments” (actin is the sliding filament anchored by Z - disc).
• For “contains protein heads that bind reversibly to a complementary protein, enabling sliding mechanism” (myosin).
• For “contains active sites to allow reversible binding of sliding mechanism” (actin).
• For “basic unit of contraction” (sarcomere).

Answer:

• Z - disc: provides anchoring for one of the sliding filaments.
• Sarcomere: basic unit of contraction.
• Myosin: contains protein heads that bind reversibly to a complementary protein, enabling sliding mechanism.
• Actin: contains active sites to allow reversible binding of sliding mechanism.