Biology II - Muscular System: Cross-Bridge Cycling

Biology II

Cross-Bridge Cycling

how myosin moves actin to make a sarcomere contract

how many stages are in cross-bride cycling

6

step 1

Ca+2 is released by the sarcoplasmic reticulum

step 2

Ca+2 binds to troponin

3 subunits: T goes to tropomyosin, C goes to Ca+2, and I goes to actin

step 3

the binding of Ca+2 causes troponin to change shape and roll tropomyosin off the myosin-binding sites

step 4

the myosin head lifts, forming a corss-bridge between the myosin head and myosin binding sites

stop 5

myosin pulls actin toward the M-line

this is called the power-stroke

step 6

ATP binds to myosin, allowing it to break he cross-bridge

steps 4-6 repeat as long as Ca+2 and ATP are present