Sliding filament model

• What is the structure of the myosin filament?

  It has a globular head region.
• What role do tropomyosin and troponin play in muscle contraction?

  They modulate the binding of myosin to actin.
• What features do myosin heads have?

  They have a hinge, actin binding site, and ATP binding site.
• What do actin filaments contain for myosin attachment?

  Actin-myosin binding sites.
• What happens to the sarcomere during muscle contraction?

  Actin filaments are pulled closer together.
• What changes occur in the I band and H-zone during contraction?

  They shorten due to increased overlap.
• What remains constant in length during muscle contraction?

  The A bands remain constant in length.
• What is the result of the simultaneous contraction of many sarcomeres?

  The entire muscle shortens and contracts.
• What does the sliding filament theory explain?

  Muscle contraction at the molecular level.
• What initiates the sliding filament theory process?

  Calcium ions bind to troponin.
• What happens to tropomyosin when calcium binds to troponin?

  Tropomyosin moves away from actin's binding sites.
• What forms when myosin heads attach to actin filaments?

  Actin-myosin cross-bridges form.
• What occurs during the power stroke of myosin heads?

  Actin filaments are pulled along, releasing ADP.
• What happens when an ATP molecule binds to the myosin head?

  Myosin detaches from actin.
• What activates myosin's ATPase activity?

  Calcium ions (Ca2+) activate it.
• What is the primary energy source for muscle contraction?

  ATP is the primary energy source.
• What is aerobic respiration suitable for?

  Prolonged, low-intensity exercise.
• When is anaerobic respiration used?

  During short, high-intensity exercise.
• What is the ATP-creatine phosphate system used for?


  Immediate ATP replenishment during vigorous exercise.
• What type of exercise utilizes creatine phosphate?

  Short bursts of vigorous exercise.
• What are the main steps in the sliding filament theory?

  1. Calcium ions bind to troponin.
  2. Tropomyosin moves away from actin's binding sites.
  3. Myosin heads attach to actin, forming cross-bridges.
  4. Myosin heads execute a power stroke, pulling actin.
  5. ATP binds to myosin, causing detachment.
  6. Myosin's ATPase activity is activated, breaking down ATP.
  7. Energy resets myosin head for reattachment.
• What are the key changes in the sarcomere during muscle contraction?

  • I band and H-zone shorten due to overlap.
  • A bands remain constant in length.
  • Sarcomeres shorten, leading to muscle contraction.
• What are the energy pathways for muscle contraction?

  • Aerobic respiration: Prolonged, low-intensity exercise.
  • Anaerobic respiration: Short, high-intensity exercise.
  • ATP-creatine phosphate system: Immediate energy for vigorous exercise.