Lecture 17

Question 1

Ca2+

Answer 1

A molecule that activates troponin to move the regulatory protein tropomyosin off the binding site of actin so myosin heads can bind move effectively for the powerstroke

Question 2

ATP

Answer 2

binds to myosin head to release from actin and hydrolyzes to provide energy to rotate into cocked position for powerstroke

Question 3

Low-force crossbridge

Answer 3

when ca2+ is not available so myosin is weakly bonded to actin binding site due to tropomyosin interference

Question 4

what is Ca2+ signalling

Answer 4

After myosin is in cocked position, ca2+ concentration rises to bind to troponin

Question 5

Stages of Ca2+

Answer 5

1. Ca2+ concentration rises
2. Calcium binds to troponin
3. Troponin move tropomyosin from myosin actin binding site
4. Myosin can fully bind to actin
5. Powerstroke will proceed

Question 6

what is the rigor state?

Answer 6

When the body is stiff due to myosin heading tightly binding to actin (very brief)

Question 7

Contraction Cycle

Answer 7

Muscle in rigor state
1. ATP binds onto myosin head to release from actin
2. ATP provides the energy for myosin head to rotate into cocked position
3. Ca2+ signalling occurs and tropomyosin is moved from myosin actin binding site and myosin has power stroke.
4. ADP falls off the myosin head and myosin is still bound to actin

Question 8

I band

Answer 8

zone of only actin

Question 9

H band

Answer 9

zone of only myosin

Question 10

A band

Answer 10

length of myosin

Question 11

M line

Answer 11

middle of the sarcomere

Question 12

Z line

Answer 12

start and end zone of sarcomere

Question 13

States of I, H, A band, and Z lines during contraction

Answer 13

shorten, shorten, remains, shortens