The cross bridge cycle

Discipline: Biology (and other Life Sciences)

Type of Paper: Question-Answer

Academic Level: Undergrad. (yrs 3-4)

Paper Format: APA

Pages: 1 Words: 275


The cross bridge cycle starts when _________. select one

1.ATP binds to troponin and is hydrolyzed to ADP and Pi

2.acetylcholine diffuses away from the synaptic cleft

3.Ca2+ is actively transported into the sarcoplasmic reticulum

4.Ca2+ from the sarcoplasmic reticulum binds to tropomyosin

5.Ca2+ from the sarcoplasmic reticulum binds to troponin

Expert Solution Answer

5.Ca2+ from the sarcoplasmic reticulum binds to troponin

Influx of sodium ions depolarizes the membrane (activation) and the membrane becomes positively charged inside. This membrane activation triggers the release of Ca2+ from the sarcoplasmic reticulum. These calcium ions bind to the troponin in the muscle filament, which causes the exposure of myosin binding sites.

Actin-myosin cross bridges are formed, actin filaments contract over the stationary myosin filaments. After the action potential ends, the Ca2+ detaches and removed by active transport into sarcoplasmic reticulum, and the muscle fiber relaxes.