$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy} $$

$$ 3 \mathrm{Na}^+ \text{ out}, 2 \mathrm{K}^+ \text{ in} $$

Question 1

Which of the following best describes the role of microtubules in the cytoskeleton?

Accepted Answer

They are hollow tubes made of α-tubulin and β-tubulin, providing tracks for motor proteins and supporting cell motility.

Question 2

A mutation disrupts the function of dynein in a cell. Which cellular process would be most directly affected?

Accepted Answer

Bending movements of cilia and flagella

Question 3

Which structure acts as the microtubule-organizing center in animal cells?

Accepted Answer

Centrosome

Question 4

What is the main difference between the beating patterns of cilia and flagella?

Accepted Answer

Cilia move in a coordinated back-and-forth pattern, while flagella move in an undulating, wave-like pattern.

Question 5

Which of the following is a function of the plasma membrane's phospholipid bilayer?

Accepted Answer

It acts as a semipermeable barrier, allowing selective passage of substances.

Question 6

How does cholesterol affect membrane fluidity at different temperatures?

Accepted Answer

Cholesterol decreases membrane fluidity at high temperatures and increases it at low temperatures.

Question 7

Which equation best represents the hydrolysis of ATP to ADP and inorganic phosphate?

Accepted Answer

$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy} $$

Question 8

A cell is placed in a hypotonic solution. What will most likely happen to the cell?

Accepted Answer

It will gain water and swell.

Question 9

Which type of membrane protein is responsible for transducing signals from outside the cell to the inside?

Accepted Answer

Receptor proteins

Question 10

Which process requires energy input from ATP to move molecules against their concentration gradient?

Accepted Answer

Active transport

Question 11

The sodium-potassium pump moves sodium and potassium ions across the plasma membrane. Which equation best describes the stoichiometry of this pump?

Accepted Answer

$$ 3 \mathrm{Na}^+ 	ext{ out}, 2 \mathrm{K}^+ 	ext{ in} $$

Question 12

Which of the following best explains why integral membrane proteins often contain alpha helices?

Accepted Answer

Alpha helices allow the protein to interact with the hydrophobic core of the lipid bilayer.

Question 13

Which type of cell junction allows the passage of ions and small molecules directly between adjacent cells, enabling communication?

Accepted Answer

Gap junctions

Question 14

A plant cell uses cytoplasmic streaming to distribute nutrients. Which cytoskeletal element is primarily responsible for this process?

Accepted Answer

Microfilaments (actin)

Question 15

Which of the following is an example of cotransport in cellular membranes?

Accepted Answer

Glucose is transported into the cell along with sodium ions using the sodium gradient.

Question 16

Which process involves the fusion of vesicles with the plasma membrane to release their contents outside the cell?

Accepted Answer

Exocytosis

Question 17

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic structure with proteins and lipids able to move laterally within the bilayer

Question 18

Which type of signaling involves hormones traveling through the bloodstream to reach distant target cells?

Accepted Answer

Endocrine signaling

Question 19

Which of the following is a real-world example of receptor-mediated endocytosis?

Accepted Answer

Uptake of cholesterol via LDL receptors

Question 20

Which equation best represents the net movement of water across a semipermeable membrane due to osmosis?

Accepted Answer

$$ \Delta \Psi = \Psi_s + \Psi_p $$

Membrane Structure & Function: Cytoskeleton and Cellular Components

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