muscle contraction Flashcards
what is a myofibril
contractile unit of skeletal muscle
what are the two protein filaments present in the myofibril
actin myosin
what are the three proteins making up actin
troponin tropomyosin
actin
what does the z line do in a myofibril
holds together the actin/ thin filament
what are the different ways of saying actin in the myofibril
thin filament
light band
actin
what is the dark band made of
myosin
what is the h zone
when there is thick and thin filaments overlapping, but there is a dark region where there is no overlap, only dark band,
what is the distance between two z lines called
sarcomere
what is the function of tropomyosin
covers and exposes myosin head binding sites on the actin molecule.
what does troponin do
changes shape when calcium is present
what is the sliding filament hypothesis
during contraction, thick and thin filaments slide past eachother.
describe the contraction cycle and role of atp in 4 steps
1- myosin head attaches to the actin filament forming a cross bridge
2- myosin head moves causing a power stroke (thin filament slide over thick filament). During a power stroke adp and pi are released from the myosin head.
3- after power stroke, new atp molecule attaches to myosin head and is hydrolysed allowing breakage of the cross bridge and reorientation of the myosin head.
4- myosin head can now make a new cross bridge further down the actin filament.
what is a cross bridge
link between myosin head and actins binding site
what are the three ways muscles maintain supply of atp
aerobic respiration-
anaerobic respiration
creatine phosphate
how does creatine phosphate (cp) create atp
acts as a reserve store of phosphate groups. phosphate can be taken from cp to ADP to create adp rapidly.
what two things occur during a power stroke
released adp and pi
causes thin and thick filaments to slide over eachother.
how does aerobic respiration miantain atp supply
oxidative phosphorylation etc..
bohr effect allows more oxygen release from hb when intense activity, limited by oxygen delivery rate.
why is anaerobic respiration not an effect source of atp for muscles
because they do give atp however, they release lactic acid which is toxic and caused fatigue.
what causes the sliding action
movement of myosin heads when attached to actin
what does tropomyosin do when muscle is stimulated
it moves and exposes the actin binding sites.
what happens to actin when action potential has entered sarcoplasmic reticulum
action potential reaches sarcoplasmic reticulum which stores calcium and causes it to be released into the sarcoplasm
calcium binds to troponin, altering its shape and causing tropomyosin to move and expose actin binding sites.
