Lecture 17

Question 1

Myosin heads have binding sites for _____.

a. tropomyosin and actin
b. actin and calcium
c. ATP and calcium
d. ATP and actin
e. tropomyosin and troponin

Answer 1

d. ATP and actin

Question 2

Identify the role(s) of ATP in muscle contraction.

Select all that apply.

a. Binds to myosin to break an actin-myosin cross-bridge
b. Provides the energy to convert myosin to a form that forms a cross-bridge with actin
c. Binds to the troponin complex to expose myosin-binding sites

Answer 2

a. Binds to myosin to break an actin-myosin cross-bridge

b. Provides the energy to convert myosin to a form that forms a cross-bridge with actin

Question 3

When an action potential from a motor neuron arrives at the neuromuscular junction (NMJ), a series of events occurs that leads to muscle contraction. Which of the following events will occur last (that is, after all of the others)?

a. depolarization of the muscle cell
b. acetylcholine (ACh) release
c. release of Ca2+ from the sarcoplasmic reticulum
d. conformational change in troponin

Answer 3

d. conformational change in troponin

Question 4

What would happen to people exposed to a chemical warfare agent that blocked acetylcholine from binding to muscle receptors?

a. Muscle contractions would be prevented, causing paralysis.
b. Action potentials would be continuously generated, causing convulsive muscle
contractions; muscle contractions would then be prevented, causing paralysis.
c. Muscle contractions could still occur, but relaxation of the muscle would be impaired.
d. Action potentials would be continuously generated, causing convulsive muscle contractions.

Answer 4

a. Muscle contractions would be prevented, causing paralysis.

Question 5

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours, due to the lack of _____.

a. sodium ions needed to fire action potentials
b. calcium ions needed to bind to troponin
c. ATP needed to break actin-myosin bonds
d. oxygen supplies needed for myoglobin

Answer 5

c. ATP needed to break actin-myosin bonds

Question 6

Most of the ATP supplies for a skeletal muscle undergoing one hour of sustained exercise come from _____.

a. substrate phosphorylation
b. creatine phosphate
c. oxidative phosphorylation
d. glycolysis

Answer 6

c. oxidative phosphorylation