BRAINCAKEThe Role of Ca2+ and ATP in Muscle Contraction
- Calcium ions have a dual role in muscle contraction.
- They bind to troponin to move tropomyosin and expose the myosin binding sites
- They activate the ATPase activity of the myosin head
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Key terms in this lesson
- actin
- A thin protein myofilament in a myofibril that, together with myosin, slides during muscle contraction; its myosin-binding sites are covered by tropomyosin in resting muscle.
- myosin
- A thick protein myofilament with a hinged globular head that binds to actin and ATP and pulls actin filaments during muscle contraction.
- tropomyosin
- A rod-shaped protein that blocks the myosin-binding sites on actin filaments in resting muscle and is moved by troponin when calcium ions bind.
- troponin
- A globular protein complex bound to tropomyosin on actin filaments that changes shape when calcium ions bind, moving tropomyosin and exposing the myosin-binding sites.
- ATP
- Adenosine triphosphate, the universal energy currency of cells, formed by adding an inorganic phosphate to ADP and hydrolysed to release energy for cellular reactions.