Contractile Mechanisms

Question 1

what is a sacromere

Answer 1

unit of contraction

Question 2

what is the I band

Answer 2

distance where myosin ends and next one begins

Question 3

what is the A band

Answer 3

distance of myosin

Question 4

Crossbridge cycle

Answer 4

• rigor state
• ATP binds to myosin head, myosin head detaches from actin
• ATP hydrolysed, tilt
• myosin binds to actin further up
• ADP released, power stroke
• back to rigor state
• actin slides along the myosin

Question 5

thin filaments

Answer 5

actin

Question 6

thick filaments

Answer 6

myosin

Question 7

after the rigor state what happens

Answer 7

ATP added to myosin head and this detaches the mysoin head from actin

Question 8

after ATP binding to myosin head what does this cause to detach

Answer 8

myosin head to actin

Question 9

what is the energy from hydrolysis of ATP used for in the crossbridge cycle

Answer 9

tilt the myosin head back

Question 10

when the phosphate is released on the cross bridge cycle what does the mysoin head do

Answer 10

bind to an actin filament further up

Question 11

when the ADP is released what happens

Answer 11

power stroke

Question 12

what is the power stroke

Answer 12

myosin head tilts back to rigor state, causing actin to slide along the myosin

Question 13

at what level of Calcium does it have to rise to to begin acting as the secondary messanger

Answer 13

100nM to 500nM

Question 14

when Ca2+ is present what does it bind to

Answer 14

troponin(TnC), causes it to undergo a conformational change, removes inhibition so myosin heads can bind

Question 15

what is calcium induced calcium release

Answer 15

small amounts of calcium in cell, Ca2+ binds to RyR, on SR opens, release of Ca2+ into cytosol