Muscle Contraction

Question 1

Using ATP hydrolysis to power a machine

Answer 1

Muscle contraction

Question 2

The basic contractile unit of muscle

Answer 2

Sarcomere

Question 3

Thin filament. Highly abundant protein

Answer 3

Actin

Question 4

Thick filament. 6 subunits. Intertwined with Dimers (coiled coils) and the heavy chain

Answer 4

Myosin

Question 5

Each monomer of actin holds a hydrolyzed ADP. ATP hydrolysis causes it to polymerize. What does the hydrolysis contribute to?

Answer 5

It contributes to F-actin stabilization. Does not contribute to movement.

Question 6

Each monomer of actin has a binding site for what?

Answer 6

Myosin

Question 7

Step 1 of muscle contraction

Answer 7

Relaxed muscle. Tropomyosin blocks myosin binding sites

Question 8

Step 2 of muscle contraction

Answer 8

After neutral signal, Ca2+ binds to troponin C, causing it to “drag” tropomyosin to the side

Question 9

Step 3 of muscle contraction

Answer 9

Once the signal of Ca2+ is received, myosin works in 4 steps.

Question 10

Myosin step 1

Answer 10

ATP binds to myosin head, causing dissociation from actin. The binding of ATP causes the head to let go

Question 11

Myosin step 2

Answer 11

ATP hydrolysis causes the head to shift back in space lightly (like a lever arm). Myosin is holding onto ADP + Pi

Question 12

Myosin step 3

Answer 12

Myosin head attaches to actin filament causing the release of Pi. The binding of the head to a DIFFERENT actin binding site.

Question 13

Myosin step 4

Answer 13

Pi release causes a “power stroke” (a conformational change in myosin head that moves actin and myosin relative to one another). This drags the actin filament in one direction. ADP is released.

Question 14

Rigor state

Answer 14

When myosin head is bound tightly to actin

Question 15

Ligand binding processes in muscle contraction

Answer 15

ATP binding myosin head, Ca2+ binding troponin, myosin head binding actin subunits, actin binding of ATP