muscle contraction Flashcards
what is creatine phosphate
a compound in muscle that acts as a store of phosphates and can supply phosphates to make atp rapid
what are the two types of protein filament in myofibril
- thin filaments- actin, light band
-thick filaments - myosin, dark band
what dpes the z line do
separate individual sacromeres.
hold together the light bands
what is the distance between the two z lines
sacromere
what surrounds the thick and thin filaments in a myofibril
sarcoplasmic reticulum
what is the I band
describe the srtucture of actin
two chains of actin subunits, twisted.
tropomyosin is wound around actin
troponin are globular molecules attached to tropomyosin.
what is troponin and its structure
troponin is a globular protein which binds to tropomyosin.
consists of three polypeptides-
1 bind to actin
1 bind to tropomyosin 1 binds to calcium ions when available
what type of protein in troponin
globular- has 3 polypeptides
what is the structure of myosin
each myosin has two protruding mobile myosin heads, which stick out.
these heads bind to actin when binding sites are exposed
what is the sliding filament hypothesis
when contraction happens-
- z lines move closer together
- sarcomere shortens
- h zone and light bands get shorter
meaning the thin and thick filaments slide across eachother
what is the h zone
middle of dark band where there is no overlap
how is the sliding movement of muscles caused
movement of myosin head.
when muscle stimulated, tropomyosin is moved aside, exposing binding sites on the acting. The myosin heads attach and move, causing actin to slide past myosin
what band and zone gets shorter during contraction
light band
h zone
describe muscles and zones during relaxation
h zone is larger
sarcomere is long
light band gets shorter
when muscle is stimulated, where does action potential pass along
along sarcolemma
t tubules
into muscle fibre then to the sarcoplasmic reticulum which stores calcium
what part of the muscle fibre stores calcium ions needed for contraction
sarcoplasmic reticulum
what happens when action potential reachoes sarcoplasmic reticulum
it releases calcium ions into the sarcoplasm, calcium then binds to troponin causing it to change shape and moving tropomyosin and expose binding sites
what causes tropomyosin to move and expose binding sites of actin so
calcium ions which were released into the sarcoplasms bind to the troponin and alter it shape and tropomyosin is moved and pulled to the side
what ions bind to troponin and change its shape to allow tropomyosin to change shape and expose binding sites of actin
calcium ions bind to troponin and change its shape
what is formed between myosin heads and exposed actin sites when they are joined together
cross bridges
what happens with calcium ions after contraction
they are rapidly pumped back into the sarcoplasmic reticulum allowing relaxation of the muscle
what is the power stroke does part of the myosin head act as
ATPase,
can hydrolyse ATP to ADP and pi
what is the power stroke
when the myosin head moves causing the actin filament to pass the myosin filament - POWER STROKE
during this adp and pi are relased from the head.
what product is made after the power stroke
a new atp molecule
after the power stroke a new atp molecule is created.
what does the atp molecule do
it attaches to the myosin head and breaks the cross bridge and allows it to return to its original position..
myosin head can now make a new cross bridge with along the actin filament
what is creatine phosphate
in sarcoplasm
acts as a storage of phosphate groups, which can quickly be added to adp molecules to rapidly produce atp.
why is anaerobic respiration in muscle tissue bad
becuase it can lead to lactic acid production, which is toxic and causes fatigue
