Muscles

Which molecules bind to the actin molecule in a way that prevents a myosin head from forming a cross bridge?

• Myosin

• Actin

• Troponin-Tropomyosin

Which molecule supplies energy for the flexing of the myosin head "power stroke".

• calcium

• ATP

• sodium

Which molecule has a movable head that grabs and provides a power stroke when activated?

• Myosin

• Actin

• Troponin-Tropomyosin

Which molecule forms the majority of the thin filament?

• Myosin

• Actin

• Troponin-Tropomyosin

What molecule binds to the blocking molecules, causing them to move and expose the myosin binding site?

• calcium

• sodium

• ATP

Another name for a muscle cell

• myofibril

• sarcomere

• muscle fiber

The contractile element of the fiber. It is contained between two Z-lines (disks).

• sarcomere

• muscle fiber

• cardiac muscle

What happens to the H zone during a sarcomere contraction?

• It disappears
• It gets closer together
• It gets bigger
• None of these

Only thick filaments present

• Sarcomere
• H zone
• M line 
• Z disc

The functional unit of the muscle cell is the: 

• Sarcomere
• Osteon
• Myofilament
• Muscle fiber