Question

When a motor neuron triggers a muscle fiber to contract, _________ion is released from the __________________________________. This ion binds to the ________________, which pushes the tropomyosin aside, exposing the ___________________________on the actin filaments.   If ____________is present, it will bind to a myosin head and release energy, causing a change in shape (the high-energy configuration). This myosin head then forms a ___________________with the actin filament.   ___________and __________ are released, and the myosin head returns to its normal shape (_________________________), which makes the actin filament slide with respect to the _________ filament. With many of these events happening along the muscle fiber, an overall muscle contraction is achieved.

Answer 1

Please find the answers for the blank spaces as below:

Actin-myosin interact with troponin for movement of the muscle fibres under the action of calcium ions in the cytoplasm. With the release of calcium from sarcoplasmic reticulum into the cytosol, the troponin activation starts by binding of the calcium and thus consequent release of tropomyosin. This causes the myosin to undergo structural conformational change in the presence of ATP thus leading to release of ADP and Pi. The ADP is recylced along with Pi for again taking part in this reaction and thus releasing the actin and myosin fibres apart.

1. Calcium (Ca²⁺)
2. Sarcoplasmic reticulum
3. Troponin
4. Binding/active sites of troponin
5. ATP (source of energy)
6. connection by bridging
7. ADP and inorganic phosphate
8. for recycling to the complex or rebinding with the complex
9. myosin