Q: Which equation correctly represents the energy conversion by motor proteins such as kinesin and dynein?

$$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{mechanical work}$$

Question 1

Which of the following best describes the primary function of kinesin motor proteins in eukaryotic cells?

Accepted Answer

They move vesicles toward the plus end of microtubules.

Question 2

A mutation disrupts the ATPase activity of the kinesin head domain. Which cellular process would be most directly affected?

Accepted Answer

Vesicle transport along microtubules

Question 3

Which equation correctly represents the energy conversion by motor proteins such as kinesin and dynein?

Accepted Answer

$$	ext{ATP} ightarrow 	ext{ADP} + 	ext{P}_i + 	ext{mechanical work}$$

Question 4

A patient with immotile cilia syndrome (primary ciliary dyskinesia) is likely to have defects in which of the following axonemal structures?

Accepted Answer

Dynein arms

Question 5

Which of the following best explains why the addition of ATP to isolated axonemes with broken nexin links causes the axoneme to telescope to many times its original length?

Accepted Answer

Dynein arms walk along adjacent microtubule doublets without resistance

Question 6

Which of the following is a key difference between cilia and flagella in eukaryotic cells?

Accepted Answer

Flagella are generally longer and fewer per cell than cilia.

Question 7

During muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The I band shortens while the A band remains constant.

Question 8

Which protein binds calcium ions to initiate the conformational change that allows muscle contraction?

Accepted Answer

Troponin C

Question 9

A vesicle needs to be transported from the Golgi apparatus to the plasma membrane. Which motor protein is most likely responsible for this movement?

Accepted Answer

Kinesin

Question 10

Which of the following best describes the 'hand-over-hand' model of kinesin movement?

Accepted Answer

One head moves past the other, alternating leading and trailing positions.

Question 11

Which of the following is the correct sequence of events in the cross-bridge cycle during muscle contraction?

Accepted Answer

Myosin head binds actin, Pi release, power stroke, ADP release, ATP binding

Question 12

Which of the following best explains why a decrease in cytosolic Ca$$^{2+}$$ concentration leads to muscle relaxation?

Accepted Answer

Troponin loses Ca$$^{2+}$$, allowing tropomyosin to block myosin binding sites on actin.

Question 13

Which of the following is a function of the protein titin in the sarcomere?

Accepted Answer

Links thick filaments to the Z line and provides elasticity

Question 14

Which of the following best describes the role of nexin links in the axoneme of cilia and flagella?

Accepted Answer

They restrict sliding of microtubule doublets, converting sliding into bending.

Question 15

A scientist observes that vesicles in a neuron are moving toward the cell body. Which motor protein is most likely responsible for this movement?

Accepted Answer

Dynein

Question 16

Which of the following best explains the process of chemotaxis in a neutrophil?

Accepted Answer

The cell forms actin-rich protrusions toward a higher concentration of chemoattractant.

Question 17

Which of the following is a shared characteristic of all motor proteins?

Accepted Answer

They convert chemical energy into motion.

Question 18

Which of the following proteins is responsible for capping the plus end of actin filaments in the sarcomere?

Accepted Answer

CapZ

Question 19

Which of the following best describes the role of the sarcoplasmic reticulum in muscle contraction?

Accepted Answer

It stores and releases Ca$$^{2+} to $$regulate contraction.

Cell Motility: Microtubule- and Actin-Based Movement in Eukaryotic Cells

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