Q: Which of the following equations correctly represents the diameter of a microtubule and its lumen?

$$\text{Outer diameter} = 25\ \text{nm}$$, $$\text{Lumen (inner diameter)} = 15\ \text{nm}$$

Question 1

Which of the following best describes the primary function of the cytoskeleton in eukaryotic cells?

Accepted Answer

It provides mechanical support, maintains cell shape, enables cell motility, mediates intracellular transport, and regulates biochemical activities by transmitting mechanical forces.

Question 2

Microtubules are composed of which protein subunits, and how do they assemble?

Accepted Answer

They are composed of a- and ß-tubulin subunits that polymerize into a-ß dimers, which then assemble into hollow tubes.

Question 3

Which of the following equations correctly represents the diameter of a microtubule and its lumen?

Accepted Answer

$$	ext{Outer diameter} = 25\ 	ext{nm}$$, $$	ext{Lumen (inner diameter)} = 15\ 	ext{nm}$$

Question 4

A researcher observes a cell with numerous short, hair-like projections that beat rapidly back and forth. Which structure is most likely being observed, and what is its core arrangement?

Accepted Answer

Cilia; 9 doublets of microtubules arranged in a circle with 2 single microtubules in the center (9+2 structure)

Question 5

Which of the following best explains how dynein arms contribute to the movement of cilia and flagella?

Accepted Answer

Dynein arms hydrolyze ATP, attach to adjacent microtubule doublets, and cause them to slide against each other, resulting in bending.

Question 6

Which of the following statements about centrosomes and centrioles is correct?

Accepted Answer

Centrosomes in animal cells contain two centrioles arranged at a 90° angle, each made of 9 sets of 3 microtubules.

Question 7

During muscle contraction, which two proteins interact, and what is the result of their interaction?

Accepted Answer

Actin and myosin interact, causing the cell to shorten as filaments slide past each other.

Question 8

Which of the following best describes the function of microfilaments in the process of cytoplasmic streaming in plant cells?

Accepted Answer

Microfilaments interact with myosin to create a gel-sol transition, enabling the circular movement of cytoplasm and distribution of materials.

Question 9

A mutation disrupts the formation of the basal body in a sperm cell. Which of the following is the most likely consequence?

Accepted Answer

The sperm will be unable to form a functional flagellum, resulting in impaired motility.

Question 10

Which of the following is a key difference between microtubules and microfilaments?

Accepted Answer

Microtubules resist compression and are made of tubulin, while microfilaments resist tension and are made of actin.

Question 11

Which of the following best explains why plant cells do not have centrioles, but can still organize microtubules for cell division?

Accepted Answer

Plant cells have microtubule organizing centers (MTOCs) that function similarly to centrosomes but lack centrioles.

Question 12

A cell is observed to have projections that increase its surface area for absorption. Which cytoskeletal element is most abundant in the core of these projections?

Accepted Answer

Microfilaments (actin filaments)

Question 13

Which of the following best describes the process by which microtubules grow and shrink within the cell?

Accepted Answer

Microtubules assemble and disassemble by adding or removing a-ß tubulin dimers at their ends.

Question 14

Which of the following scenarios best illustrates the role of the cytoskeleton in intracellular transport?

Accepted Answer

Vesicles move from the Golgi apparatus to the plasma membrane along microtubules.

Question 15

Which of the following is the correct molecular structure of the axoneme found in cilia and flagella?

Accepted Answer

9 outer doublets of microtubules arranged in a circle with 2 central single microtubules (9+2 structure)

Question 16

Which of the following best explains the difference in movement between cilia and flagella?

Accepted Answer

Cilia move with a back-and-forth oar-like motion, while flagella undulate in a wave-like motion.

Question 17

A patient has a genetic defect in the dynein protein. Which of the following symptoms would most likely be observed?

Accepted Answer

Impaired movement of cilia and flagella, leading to respiratory and reproductive issues.

Question 18

Which of the following best describes the role of microfilaments in amoeboid movement?

Accepted Answer

Microfilaments interact with myosin to create localized contractions, allowing the cell to extend pseudopodia and move.

The Cytoskeleton: Structure, Components, and Functions

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