Sliding Filament Theory

What is the basic functional unit of a muscle fibre?

• Myofibril

• Sarcomere

• Actin

• Myosin

Which protein filament pulls on the other during muscle contraction?

• Actin

• Myosin

• Troponin

• Tropomyosin

Which ion is needed to initiate muscle contraction?

• Sodium

• Potassium

• Calcium

• Magnesium

What molecule provides the energy for muscle contraction?

• ATP

• ADP

• Glucose

• Fats

Which of the following happens when calcium binds to troponin?

• a) Myosin heads detach from actin

• b) Tropomyosin exposes binding sites on actin

• c) ATP binds to myosin

• d) Sarcomere elongates

What part of the sarcomere shortens during muscle contraction?

• a) A-band

• b) Z-line

• c) I-band

• d) H-zone

During muscle contraction, the myosin head forms a cross-bridge with which protein?

• a) Tropomyosin

• b) Troponin

• c) Actin

• d) Calcium

Which structure stores and releases calcium in muscle cells?

• a) Mitochondria

• b) Sarcoplasmic reticulum

• c) Nucleus

• d) Golgi apparatus

What happens to ATP after it binds to the myosin head during muscle contraction?

• a) It is stored as energy

• b) It is broken down into ADP and Pi, releasing energy

• c) It causes calcium to be released

• d) It prevents muscle contraction