Actin and Myosin

The organelle containing actin and myosin identified as #9

• ACh

• Sarcolemma

• Vesicle

• Myofibril

What is a crossbridge?

• Where myosin binds to actin

• Where the calcium crosses into the cytoplasm

• Where calcium binds with troponin

• None of the answers are correct.

Calcium:

• causes ATP binding to actin

• increases the action potential along the sarcolemma

• binds to proteins on myosin

• triggers the binding of myosin to actin

___forms a crossbridge with actin.

• actin

• myosin

• calcium

• ATP

____________ attaches to actin to form the cross bridge.

• Troponin

• Tropomyosin

• Myosin

• Calcium

the disassociation of the myosin cross-bridge is directly activated by which of the following?

• the attachment of ATP to myosin heads

• the hydrolysis of ATP

• repolarization of the T-tubules

• Ca2+ is shuttled back out of the cell

Match the following:

• Thin fibers

• Actin

• Thick fibers

• Myosin

• Muscle fibers

• Myofibrils

What happens to a sarcomere during a myosin power stroke?

• A sarcomere, H zone, & I band shortens during the power stroke.

• A sarcomere, H zone & I band lengthen during the power stroke

• A sarcomere length is unchanged

• The sarcomere, H zone and A band shorten during the power stroke

What is the length between Z-lines of an actin molecule called?

• fascicle

• sarcomere

• myosin binding site

• sarcoplasmic length

During muscle contraction the myosin and actin filaments do not change length.

• True

• False

Answer explanation

They do not shorten, they just overlap more.