Question 1

Which of the following best explains why cells are generally small in size?

Accepted Answer

Smaller cells have a higher surface area-to-volume ratio, allowing more efficient exchange of materials with their environment.

Question 2

A spherical cell has a radius that increases from 1 to 3 units. What happens to its surface area and volume?

Accepted Answer

Surface area increases by a factor of 9, volume increases by a factor of 27.

Question 3

Calculate the surface area-to-volume ratio for a cubic cell with sides of 4 mm. Use the formulas $$SA = 6a^2$ and V$$ = $$a^3.$$

Accepted Answer

$$SA:V = \frac{96}{64} = 1.5$$

Question 4

Which component of the plasma membrane is responsible for its selective permeability?

Accepted Answer

The hydrophobic fatty acid tails of phospholipids prevent passage of polar molecules.

Question 5

Which of the following molecules can pass directly through the phospholipid bilayer without the help of membrane proteins?

Accepted Answer

O$$_2$$ and CO$$_2$$

Question 6

What is the main function of membrane carbohydrates?

Accepted Answer

Cell-cell recognition and distinguishing neighboring cells.

Question 7

Which statement best describes facilitated diffusion?

Accepted Answer

It is the passive movement of molecules from high to low concentration with the help of membrane proteins.

Question 8

A nerve cell needs to quickly move Na$$^+$$ ions into the cell. Which membrane transport mechanism is most likely involved?

Accepted Answer

Facilitated diffusion through ion-gated channels.

Question 9

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

Accepted Answer

Active transport

Question 10

What is the role of the Na$$^+/K$^+$$ ATPase in maintaining membrane potential?

Accepted Answer

It pumps 3 Na$$^+$$ out and 2 K$$^+ in$$, creating a charge gradient across the membrane.

Question 11

Which of the following best describes osmoregulation in cells?

Accepted Answer

It maintains water balance and allows organisms to control their internal solute composition.

Question 12

A cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

Water will move out of the cell by osmosis, causing the cell to shrink.

Question 13

Which of the following is NOT a function provided by membrane proteins?

Accepted Answer

Synthesis of DNA

Question 14

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

Accepted Answer

A dynamic structure with proteins and phospholipids that move and change positions within the bilayer.

Question 15

Which of the following is a real-life example of bulk transport in cells?

Accepted Answer

White blood cell engulfing bacteria by phagocytosis.

Question 16

Which equation correctly calculates the surface area of a sphere?

Accepted Answer

$$SA = 4\pi r^2$

Question 17

Which of the following statements about membrane permeability is correct?

Accepted Answer

Small nonpolar molecules pass freely across the membrane, while large polar molecules require transport proteins.

Question 18

Which process is used by cells to release substances to the outside environment?

Accepted Answer

Exocytosis

Question 19

What is the effect on the surface area-to-volume ratio as the size of a cell increases?

Accepted Answer

The surface area-to-volume ratio decreases.

Question 20

Which of the following best describes the role of aquaporins in the cell membrane?

Accepted Answer

They facilitate the rapid movement of water across the membrane.

Cell Size, Plasma Membrane Structure, and Membrane Transport Mechanisms

Study Guide - Practice Questions