IB Biology: B3.3-Sliding Filament Model of Muscle Contraction

What is the primary function of skeletal muscles?

• To produce heat for body temperature regulation.

• To pump blood throughout the body.

• To pull on bones to allow for body movement.

• To store energy in the form of fat.

Which of the following is the smallest contractile unit within a muscle fiber?

• Muscle fiber

• Myofibril

• Sarcomere

• Connective tissue

What is the immediate effect of calcium ions (Ca²⁺) being released during muscle contraction?

• They directly cause myosin heads to pull on actin.

• They bind to troponin, moving tropomyosin to expose myosin-binding sites.

• They provide the energy for the myosin head to reattach to actin.

• They break the cross-bridge between myosin and actin.

What is one of the primary roles of ATP in the cross-bridge cycle of muscle contraction?

• To cause the myosin head to detach from actin.

• To bind directly to troponin, initiating contraction.

• To directly pull the actin filament.

• To block the myosin-binding sites on actin.