The cross bridge cycle starts when _________. Select the best answer. View Available Hint(s) Select the best answer. ATP binds t
o troponin and is hydrolyzed to ADP and Pi Ca2+ from the sarcoplasmic reticulum binds to troponin acetylcholine diffuses away from the synaptic cleft Ca2+ is actively transported into the sarcoplasmic reticulum Ca2+ from the sarcoplasmic reticulum binds to tropomyosin
The answer is; Ca2+ from the sarcoplasmic reticulum binds to tropomyosin
When the ca2+ ions bind to the tropomyosins on the actin filament, the tropomyosins are displaced and this exposed the myosin binding sites on the actin filament. The ADP + Pi (attached to the myosins heads), from the previous cycle, is released allowing the cocking of the myosin heads hence pulling on the actin filament. ATP then binds on the ATP-site on the myosin heads casing a release of the myosin heads from their site in the actin. This also hydrolyzes the ATP. This is one cycle of the cross-bridge cycle.
If the expression of a trait requires only one copy of a gene (one allele), that trait is considered dominant. If the expression of a trait requires 2 copies of a gene (2 alleles), that trait is considered recessive. One exception is X-linked disorders.