Question 1

Which component of the plasma membrane is primarily responsible for its selective permeability, and why?

Accepted Answer

Phospholipid bilayer, because its hydrophobic core prevents passage of water-soluble substances.

Question 2

A cell is placed in a solution and water moves into the cell. Which process is responsible for this movement, and what type of solution is the cell in?

Accepted Answer

Osmosis; hypotonic solution

Question 3

During which phase of the cell cycle does DNA replication occur, and what is the main purpose of this phase?

Accepted Answer

S phase; to duplicate the genetic material for cell division

Question 4

Which of the following best describes the role of cholesterol in the plasma membrane?

Accepted Answer

It makes the membrane more rigid and less permeable to small water-soluble molecules.

Question 5

A white blood cell engulfs a bacterium by surrounding it with its plasma membrane. Which process is this, and what type of transport does it represent?

Accepted Answer

Phagocytosis; active transport

Question 6

Which of the following events occurs during metaphase of mitosis?

Accepted Answer

Chromosomes align along the metaphase plate.

Question 7

A patient’s cells are unable to move glucose into the cell against its concentration gradient. Which cellular process is most likely impaired?

Accepted Answer

Active transport

Question 8

Which of the following best explains why oxygen can diffuse freely across the plasma membrane?

Accepted Answer

Oxygen is small and nonpolar, allowing it to pass through the hydrophobic core.

Question 9

What is the main difference between facilitated diffusion and active transport?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient without energy input, while active transport moves substances against their gradient using ATP.

Question 10

During which phase of mitosis do sister chromatids separate and move toward opposite poles of the cell?

Accepted Answer

Anaphase

Question 11

A cell is observed to be synthesizing proteins and duplicating organelles, but not yet replicating its DNA. In which phase of the cell cycle is this cell?

Accepted Answer

G1 phase

Question 12

Which of the following best describes the structure of a phospholipid in the plasma membrane?

Accepted Answer

A hydrophilic head and two hydrophobic tails

Question 13

Which process is responsible for the secretion of hormones from endocrine cells into the bloodstream?

Accepted Answer

Exocytosis

Question 14

If a cell remains in the G0 phase, what does this indicate about its activity?

Accepted Answer

It is performing specialized functions and not preparing to divide.

Question 15

Which of the following is true about the nuclear envelope during mitosis?

Accepted Answer

It disintegrates during prophase and reforms during telophase.

Question 16

A cell is exposed to a toxin that prevents spindle fiber formation. Which stage of mitosis will be directly affected first?

Accepted Answer

Prophase

Question 17

Which of the following best describes receptor-mediated endocytosis?

Accepted Answer

A process where specific molecules bind to receptors and are then internalized by the cell.

Question 18

Which of the following equations best represents the movement of molecules during diffusion?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Question 19

Which statement best explains why facilitated diffusion is necessary for glucose transport into most cells?

Accepted Answer

Glucose is a large, polar molecule that requires a carrier protein to cross the hydrophobic membrane.

Question 20

Which phase of the cell cycle is characterized by the condensation of chromatin into chromosomes and the breakdown of the nuclear envelope?

Accepted Answer

Prophase

The Cell: Plasma Membrane Transport and Cell Cycle/Mitosis

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