Power Stroke and Sliding of Actin Filaments
Explains the pulling action of the myosin head, causing the actin filaments to slide past myosin, leading to sarcomere shortening.
What is Power Stroke and Sliding of Actin Filaments?
The basic contractile unit of striated muscle, extending from one Z-line to the next.
Key points
- Explain the mechanism of the power stroke.
- Describe how actin filaments slide over myosin filaments.
- Relate sarcomere shortening to muscle contraction.
- Identify the roles of Ca²⁺, ATP, troponin, and tropomyosin in the process.
Common exam trap
Confusing the role of ATP in detachment versus re-cocking.
Definitions
- Term
Sarcomere
- Meaning
The basic contractile unit of striated muscle, extending from one Z-line to the next.
- Term
Power Stroke
- Meaning
The conformational change in the myosin head that pulls the actin filament towards the M-line during muscle contraction.
- Term
Sliding Filament Theory
- Meaning
The theory that muscle contraction occurs by the sliding of actin filaments over myosin filaments, without shortening of the filaments themselves.
- Term
Cross-bridge
- Meaning
The temporary connection formed between the myosin head and actin filament during muscle contraction.
Learning objectives
Explain the mechanism of the power stroke.
Describe how actin filaments slide over myosin filaments.
Relate sarcomere shortening to muscle contraction.
Identify the roles of Ca²⁺, ATP, troponin, and tropomyosin in the process.
Prerequisites
Structure of a sarcomere (actin and myosin filaments, Z-lines, M-line).
Role of ATP in cellular processes.
Basic understanding of protein interactions.
Common mistakes
Confusing the role of ATP in detachment versus re-cocking.
Forgetting the role of calcium ions and troponin-ponin-tropomyosin complex.
Assuming myosin filaments move; it is the actin filaments that slide.
Not understanding that the power stroke is a conformational change of the myosin head.
Keywords
Muscle Contraction
Sliding Filament Theory
Power Stroke
Actin
Myosin
Sarcomere
Cross-bridge Cycling
ATP
Calcium Ions
Troponin
Tropomyosin
Practice preview
During muscle contraction, the power stroke involves:…
easy
The force generated during the power stroke is a result of:…
medium
Which event directly follows the binding of the energized myosin head to actin during the cross-bridge cycle?…
easy