Sliding Filament Theory

Which protein forms the thick filaments in a sarcomere and is responsible for pulling actin during muscle contraction?

• Actin

• Myosin

• Troponin

• Tropomyosin

What is the name of the repeating structural unit of a muscle fibre that shortens during contraction?

• Sarcomere

• Mitochondrion

• Neuron

• Synapse

Which ion is released from the sarcoplasmic reticulum to initiate muscle contraction?

• Sodium

• Potassium

• Calcium

• Magnesium

What is the role of ATP during the recharging stage of the sliding filament theory?

• Binds to actin to expose binding sites

• Detaches myosin from actin and re-cocks the myosin head

• Releases calcium from the sarcoplasmic reticulum

• Blocks the active site on actin

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

• Myosin

• Troponin

• Tropomyosin

• Actin

What triggers the release of calcium ions from the sarcoplasmic reticulum?

• Action potential

• ATP hydrolysis

• Muscle relaxation

• Troponin binding

During which stage of the sliding filament theory does the myosin head pull the actin filament towards the centre of the sarcomere?

• Activation

• Contraction

• Recharging

• Relaxation

Which molecule binds to troponin to cause a conformational change that moves tropomyosin away from actin’s binding sites?

• Sodium

• Potassium

• Calcium

• ATP

What happens to the sarcomere during muscle contraction?

• It lengthens

• It shortens

• It remains the same length

• It disappears

Which of the following best describes the relaxation stage of the sliding filament theory?

• Myosin heads bind to actin

• Calcium is pumped back into the sarcoplasmic reticulum

• ATP is hydrolysed to ADP and phosphate

• Troponin binds to calcium