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, which allows for more efficient exchange of materials with their environment.

Question 2

A cell with a surface area of $$54\ 	ext{units}^2$$ and a volume of $$27\ 	ext{units}^3$$ has a surface area-to-volume ratio of:

Accepted Answer

$$2:1$$

Question 3

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

Accepted Answer

The phospholipid bilayer, due to its hydrophobic core, restricts passage of many substances.

Question 4

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

Accepted Answer

A bilayer of phospholipids with proteins and other molecules embedded and able to move laterally within the layer.

Question 5

Which of the following is an example of passive transport across a plasma membrane?

Accepted Answer

Oxygen diffusing from an area of high concentration outside the cell to a lower concentration inside the cell.

Question 6

What property of biological membranes allows them to regulate the passage of substances across them?

Accepted Answer

Selective permeability

Question 7

Which of the following statements about diffusion is correct?

Accepted Answer

Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration due to random motion.

Question 8

A red blood cell placed in pure water will swell and burst. Which process is responsible for this outcome?

Accepted Answer

Osmosis, as water moves into the cell where solute concentration is higher.

Question 9

Which of the following best describes the role of transport proteins in the plasma membrane?

Accepted Answer

They facilitate the movement of specific molecules across the membrane, sometimes against a concentration gradient.

Question 10

Which of the following scenarios illustrates facilitated diffusion?

Accepted Answer

Glucose molecules moving into a cell through a specific channel protein down their concentration gradient.

Question 11

If a cell's surface area increases by a factor of 4, by what factor does its volume increase, assuming the cell maintains the same shape?

Accepted Answer

By a factor of 8

Question 12

Which of the following is NOT a function of the plasma membrane?

Accepted Answer

Synthesizing DNA for the cell

Question 13

Which part of a phospholipid is hydrophobic?

Accepted Answer

The fatty acid tails

Question 14

A solution with a higher concentration of solutes compared to the inside of a cell is called:

Accepted Answer

Hypertonic

Question 15

Which of the following best explains why the spontaneous formation of membranes was a critical step in the origin of life?

Accepted Answer

Membranes allowed for the separation of internal cell environments from external surroundings, enabling the development of self-replicating molecules.

Question 16

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of water across a selectively permeable membrane.

Question 17

Which of the following would most likely increase the fluidity of a plasma membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids.

Question 18

A cell is placed in a solution and water moves out of the cell. What can you conclude about the solution?

Accepted Answer

The solution is hypertonic relative to the cell.

Question 19

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

Accepted Answer

It helps maintain membrane fluidity at different temperatures.

Question 20

Which of the following is true about carrier proteins involved in facilitated diffusion?

Accepted Answer

They transport specific molecules across the membrane without using cellular energy.

Cell Membranes: Structure, Function, and Transport Mechanisms

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