Muscle Contraction Flashcards
What does tropomyosin cover when muscles are relaxed?
binding sites on actin
Where are Ca2+ ions released from?
sarcoplasmic reticulum
What do the Ca2+ ions cause?
causes tropomyosin to move and expose the binding sites on actin (by binding to troponin)
What can happen when the binding sites are exposed?
myosin heads can bind to the binding sites on actin, forming a crossbridge
What happens after a crossbridge is formed?
tension occurs as a result of the angle, which leads to the actin being pulled and sliding along the myosin
What can happen when the binding sites are exposed?
myosin heads can bind to the binding sites on actin, forming a crossbridge
What does the sliding movement of actin result in?
the release of ADP and Pi
What happens when a new ATP molecule binds to the myosin head?
the myosin head changes shape slightly, meaning the binding site is no longer complementary so myosin detaches from the actin
What enzyme is found in the sarcoplasm?
ATPase
What does the ATPase do in the context of muscle contraction?
hydrolyses the ATP on the myosin head causing the shape to return to normal, therefore it is once again complementary to actin
What activates ATPase?
Ca2+ ions
What is the role of phosphocreatine?
provides phosphates to help regenerate ATP from ADP
What happens to the length of the sarcomere when the muscle contracts?
sarcomere shortens
What happens to the H-zone and I band as the muscle contracts?
it shortens
What happens to the length of the A-band as the muscle contracts?
stays constant
