1.a. The thick filament is composed of what molecule?
b. Flexing the head of this molecule provides what is known as the
2.The myosin head contains binding sites for what two molecules? a. ATP
3.Three molecules make up the thin filament.
a. Which molecule has a binding site for myosin heads?
b. Which molecule covers this binding site?
_Tropomyosin________________________________________________ c. Which molecule has a binding site for calcium ions?
4.What molecule must bind to the myosin head in order for it to disconnect with actin? _ATP________________________
5.Hydrolysis of the molecule in question 4 returns the myosin molecule to the
_High energy________________________ confirmation.
6.Binding of the myosin heads sequentially prevents __Myosin cross bridge binding__________ of the thin filament. 7.Name three roles for ATP in the contraction of muscle.
a. Energizing the power stroke of the myosin cross bridge
b. Disconnecting the myosin head from actin
c. Actively transporting calcium back to the SR
8.What molecule is connected to the Z line? _Thin filament_______ 9.Which of the following shorten during contraction? (may be more than one) a. Thin filament - does not shorten
b. Sarcomere - shortens
c. H zone - shortens
d. Thick filament – does not shorten
10.a. What is the name of the condition in which muscles become rigid after
death? _Rigor mortis________________________________
b. What is this condition due to?
Lack of ATP leads to the inability of the cells to actively pump calcium back into the sarcoplasmic reticulum, and the myosin heads are unable to detach from the actin (also requires ATP). After about 72 hours the muscles will have decomposed enough to again return to the relaxed state.