Chapter 17. ATP-driven Myosin Movement along Actin Filaments

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Animation Activity 17-26: ATP-driven Myosin Movement along Actin Filaments

1.

Remembering that a cycle can start at any step, select the correct order of the following steps in the myosin-actin cross bridge cycle:
1. ATP hydrolysis and rotation of the myosin head
2. ATP binding to the myosin head to release the myosin head from the actin filament
3. release of ADP from the myosin head
4. binding of the myosin head to the actin filament
5. release of phosphate and the power stroke

2 - 4 - 1 - 3 - 5

1 - 2 - 5 - 4 - 3

3 - 2 - 1 - 4 - 5

3 - 5 - 4 - 2 - 1

1 - 2 - 3 - 4 - 5

Correct.

Incorrect.

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2.

Each myosin head cross-bridge cycle uses energy derived from ________.

hydrolysis of the same number of ATPs as the number of light chains associated with the myosin neck region

hydrolysis of a variable number of ATPs depending on the size of the myosin step size

hydrolysis of a variable number of ATPs depending on the size of the cargo moved or the intensity of the signal for muscle contraction

hydrolysis of one ATP

hydrolysis of two ATPs

Correct.

Incorrect.

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3.

Most myosin classes are (+) end–directed motors, which can be speculated to be because ________.

during the cross-bridge cycle, the myosin power stroke moves the actin filament toward its (+) end.

all myosins pull the (+) ends of two actin filaments closer together

ATP hydrolysis generates a +/– charge gradient across the myosin head that is crucial for the cross-bridge cycle.

during the cross-bridge cycle, positive (+) charges at the (+) end of an actin filament attract the myosin heads.

during the cross-bridge cycle, when the myosin head is released from the actin filament, it binds again, this time closer to the (+) end of the actin filament.

Correct.

Incorrect.

Try Again.

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Chapter 17. ATP-driven Myosin Movement along Actin Filaments

Introduction

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