The active sites to which cross-bridges attach are found on the

A) sarcoplasmic reticulum.
B) actin myofilaments.
C) Z disks.
D) T tubules.
E) myosin myofilaments.

Active Sites

Regions on enzymes where substrate molecules bind and undergo a chemical reaction.

Cross-Bridges

The connections formed between actin filaments and myosin heads during muscle contraction, enabling force generation.

Actin Myofilaments

Thin filaments primarily composed of the protein actin, playing a crucial role in muscle contraction and cell movement.