Muscle Contraction and the Crossbridge Cycle

What is the basic functional unit of a muscle fiber?

• Actin

• Myofibril

• Sarcomere

• Fascicle

Which theory explains muscle contraction through the interaction of filaments?

• Fascicle Theory

• Muscle Fiber Theory

• Sliding Filament Theory

• Crossbridge Theory

In the rigor state, what is the relationship between myosin and actin?

• They are tightly bound

• They are not bound

• They are partially bound

• They are loosely bound

What molecule is necessary to release the myosin-actin bond?

• Calcium

• ADP

• Phosphate

• ATP

During which step is ATP hydrolyzed to ADP and inorganic phosphate?

• Step 4

• Step 2

• Step 1

• Step 3

What happens during the power stroke step of the crossbridge cycle?

• Myosin binds to a new actin

• Phosphate is released and actin is pulled

• ATP binds to myosin

• ADP is released

What is released from the myosin head during step 6 of the crossbridge cycle?

• Calcium

• Phosphate

• ATP

• ADP

Which step involves the myosin head binding to the next actin in line?

• Step 5

• Step 4

• Step 3

• Step 2

What is the angle of the myosin head during the energized state?

• 120 degrees

• 90 degrees

• 60 degrees

• 45 degrees

What two conditions are necessary for the crossbridge cycle to continue?

• Absence of ATP and calcium

• Presence of ADP and phosphate

• Presence of ATP and calcium

• Absence of ADP and phosphate