Question

The cross bridge cycle starts when _________.

a) Ca2+ is actively transported into the sarcoplasmic reticulum
b) Ca2+ from the sarcoplasmic reticulum binds to troponin
c) ATP binds to troponin and is hydrolyzed to ADP
d) Pi Ca2+ from the sarcoplasmic reticulum binds to tropomyosin
e) acetylcholine diffuses away from the synaptic cleft

Answer 1

Answer:

b) Ca2+ from the sarcoplasmic reticulum binds to troponin

Explanation:

The release of the calcium ions initiates the muscle contractions. The release is triggered from the storage in sarcoplasmic reticulum. These ions initiates contraction that is sustained by the ATP .The $Ca^{2+}$ ions from sarcoplasm bind to the troponin which drive cross-bridge cycling and pulling of the actin strands by the myosin.

Answer 2

The cross bridge cycle starts when Ca2+ from the sarcoplasmic reticulum binds to troponin.

The cross bridge cycle is known to be a series of events during which myosin heads pull thin filaments toward the the middle of the sarcomere.

In stage 1 of the Cross Bridge formation,

the powered formation myosin head attaches to an actin myofilament, forming a cross bridge.

The steps in the cycle includes:

• The activated myosin head hook itself to actin, forming a cross bridge

• ADP is released and myosin slides the thin filament to the middle of the sarcomere

• ATP hooks to the myosin head and detaches it from actin.

• ATP is hydrolyzed to ADP and P, and the energy release the myosin head.

Conclusively, a cross bridge us simply said to be formed by myosin head to hook to the actin myofilament.

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