22. Sliding Filament Theory

Which ion is essential for initiating the sliding filament mechanism in muscle contraction?

• Sodium ions

• Calcium ions

• Potassium ions

• Chloride ions

What is the basic contractile unit of a myofibril in skeletal muscle?

• Sarcomere

• Myosin

• Actin

• H zone

Which protein forms the thick filaments in the sliding filament theory?

• Actin

• Myosin

• Troponin

• Tropomyosin

What structure marks the boundary between adjacent sarcomeres?

• H zone

• I band

• A band

• Z line

Which band of the sarcomere contains only thin filaments and appears lighter under a microscope?

• A band

• I band

• H zone

• Z line

What is the function of ATPase in muscle contraction?

• Stores calcium ions

• Forms cross-bridges

• Breaks down ATP to release energy

• Binds to actin

Which protein blocks the myosin-binding sites on actin when the muscle is at rest?

• Troponin

• ATPase

• Myosin

• Tropomyosin

What is the role of troponin in muscle contraction?

• Binds to ATP

• Binds to calcium ions and moves tropomyosin

• Forms the thick filament

• Stores energy

Where are sarcomeres located?

• Muscle fibre

• Fascicle

• Perimysium

• Myofibril

What forms the cross-bridges during muscle contraction?

• Actin heads attaching to myosin

• Myosin heads attaching to actin

• Troponin binding to tropomyosin

• ATP binding to calcium