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list two classes of molecular motors
actin motors and microtubule motors
important representatives for actin motors
myosin and actin
important representatives for microtubule motors
kinesin and dynein
which motor is the prototype of motors and mediates muscle contraction?
actin motors
anterograde movement
kinesin
retrograde movement
dynein
how many subunits does myosin contain?
6 subunits - 2 heavy chains and 4 light chains
what does F actin consist of?
a filamentous polymer composed of G-actin monomers.
specifically, consists of 2 helical aggregates of G actin that are twisted around each other
what are the components of thick filaments?
myosin head and tail
head: contains ATPases that generate force
tail: 150nm
what are the components of thin filaments?
actin, troponin, tropomyosin
where thin filaments are held together by alpha-actinin, desmin, vimentin
Z disk
where adjacent thick filaments are joined tail to tail
M line
regions with thin filaments but no thick filaments
I band
four distinct steps that lead to force generation and muscle contraction
1. ATP binds to myosin head, causing dissociation from actin
2. as tightly bound ATP is hydrolyzed to ADP and Pi, a conformational change occurs
3. Myosin head attaches to actin filament, causing release of Pi
4. Pi release triggers "power stroke" which is a conformational change in the myosin head that moves both actin and myosin filaments relative to one another. ADP is released in the process
how is the force generation regulated by calcium?
when troponin C binds calcium, a conformational change occurs of the tropomyosin-troponin complex which normally blocks binding sites on actin for myosin heads
Note 
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