During muscle contraction myosin heads A Option A: walk along thin filaments toward the M disk

1. During muscle contraction myosin heads
   A
   Option A: walk along thin filaments toward the M disk.
   B
   Option B: walk along thick filaments toward the M disk.
   C
   Option C: walk along the thin filaments toward the Z disk.
   D
   Option D: walk along the thin filaments toward the H zone.
   E
   Option E: walk along thick filaments toward the Z disk.

Option C: walk along the thin filaments toward the Z disk.

2. The energy needed to drive muscle contraction comes from ATP hydrolysis that is carried out by
   A
   Option A: tropomyosin.
   B
   Option B: myosin heads.
   C
   Option C: G-actin.
   D
   Option D: F-actin.
   E
   Option E: myosin tails.

Option B: myosin heads.

3. Which statement about actin is not true?
   A
   Option A: Actin can bind ATP.
   B
   Option B: Actin filaments are polar (the ends can be distinguished).
   C
   Option C: Monomeric G-actin polymerizes to form F-actin.
   D
   Option D: Actin is a common protein in nonmuscle cells.
   E
   Option E: There are two actin genes, one for F-actin and one for G-actin.

Option E: There are two actin genes, one for F-actin and one for G-actin.

4. Which statement about myosin is not true?
   A
   Option A: Myosin contains two globular heads.
   B
   Option B: Myosin is a heterohexamer.
   C
   Option C: Myosin aggregates to form thick filaments
   D
   Option D: All of the answers above are true of myosin.
   E
   Option E: Myosin contains six different polypeptides

Option D: All of the answers above are true of myosin.

5. During muscle contraction
   A
   Option A: myosin pushes actin filaments toward the Z disk.
   B
   Option B: All of the answers above are correct.
   C
   Option C: myosin pulls actin filaments toward the M disk.
   D
   Option D: actin pushes myosin toward the M disk.
   E
   Option E: actin pulls myosin toward the Z disk.

Option C: myosin pulls actin filaments toward the M disk.

6. What are the main bonds or forces that stabilize the dimer formed by two myosin heavy chains?
   A
   Option A: hydrophobic interactions
   B
   Option B: disulfide bonds
   C
   Option C: isopeptide bonds
   D
   Option D: hydrogen-bonds
   E
   Option E: ionic interactions

Option A: hydrophobic interactions

7. Which of the statements about muscle contraction is not true?
   A
   Option A: During muscle contraction the I band becomes shorter.
   B
   Option B: During muscle contraction the sarcomere becomes shorter.
   C
   Option C: During muscle contraction the distance between the Z disk and the M disk becomes shorter.
   D
   Option D: During muscle contraction the A band becomes shorter.
   E
   Option E: During muscle contraction the H zone becomes shorter.

Option D: During muscle contraction the A band becomes shorter.

8. Which of the statements about muscle contraction is correct?
   A
   Option A: During muscle contraction the distance between the Z disk and the M disk becomes shorter.
   B
   Option B: All of the answers above are correct.
   C
   Option C: During muscle contraction the I band becomes shorter.
   D
   Option D: During muscle contraction the sarcomere becomes shorter.
   E
   Option E: During muscle contraction the H zone becomes shorter.

Option B: All of the answers above are correct.

9. Muscle contraction is directly caused by
   A
   Option A: structural changes in the Z disk.
   B
   Option B: structural changes in myosin.
   C
   Option C: None of the above is correct.
   D
   Option D: structural changes in actin.
   E
   Option E: thick and thin filaments sliding past each other.

Option E: thick and thin filaments sliding past each other

10. The repeating functional unit in a myofibril is called
    A
    Option A: the M disk.
    B
    Option B: the A band.
    C
    Option C: the I band.
    D
    Option D: the H zone.
    E
    Option E: the sarcomere.

Option E: the sarcomere.