Question

Choose four items from the following list. For the four items you choose, describe their roles in skeletal muscle contraction.

List to choose from:

• acetylcholine
• actin
• ATP
• Ca²⁺
• myosin
• sarcomere
• SR (sarcoplasmic reticulum)
• T-tubules
• troponin
• tropomyosin

Answer 1

i) Acetylcholine (Ach) role in roles in skeletal muscle contraction. Ach is a neurotransmitter, it diffuses across the junction between two neurons (synapse) and triggers an action potential in the muscle fiber. For the skeletal muscle contraction, this must require.

ii) Actin and myosin: Muscles are made up of the muscle fiber units and they mainly have two types of proteins, they are actin and myosin. Muscles contract after receiving the signal from the nerves by the interaction between the actin and myosin filaments. This process generates movement. Myosin acts as a motor that drives filament sliding as it interacts with the actin filaments.

iii) ATP plays a very significant role in the movement of myosin and actin in a coordinated manner. ATP prepares the myosin proteins for binding with actin by moving it to a higher- energy state. Actin molecules are bound to the myosin, now the ATP must break this cross-bridge, this will enable the myosin to rebind to actin at the next muscle contraction.

iv) Role of Ca2+:

Ca2+ in low level- cross-bridge cycle stops.

Ca2+ level rise- This molecule bind to troponin, this causes a conformational change, this exposes the binding sites by moving the tropomyosin. This allows cross-bridges and contraction to occur.