Question 1

Which of the following best describes the structure of the phospholipid bilayer in cell membranes?

Accepted Answer

A double layer of phospholipids with hydrophilic heads facing the aqueous environments inside and outside the cell, and hydrophobic tails facing each other.

Question 2

Which function is NOT performed by proteins embedded in the cell membrane?

Accepted Answer

Providing structural support to the cell wall.

Question 3

A scientist observes that a cell membrane remains fluid at low temperatures. Which molecule is most likely present in higher amounts to account for this property?

Accepted Answer

Cholesterol

Question 4

Which statement best explains the 'fluid mosaic model' of cell membranes?

Accepted Answer

Membranes consist of a double layer of phospholipids with proteins and other molecules embedded and able to move laterally.

Question 5

Which of the following is an example of facilitated diffusion?

Accepted Answer

Glucose entering a cell through a specific membrane protein.

Question 6

A cell is placed in a solution with a higher concentration of solutes than inside the cell. What will most likely happen due to osmosis?

Accepted Answer

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

Question 7

Which equation correctly represents the relationship between surface area and volume for a spherical cell?

Accepted Answer

$$SA = 4 \pi r^2$

Question 8

Why do cells tend to be small in size?

Accepted Answer

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

Question 9

Which process requires energy input from ATP to move molecules across the cell membrane?

Accepted Answer

Active transport

Question 10

A cell engulfs a large particle by wrapping its membrane around it and forming a vesicle. What is this process called?

Accepted Answer

Endocytosis

Question 11

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

Accepted Answer

They act as a glycocalyx for cell recognition and adhesion.

Question 12

If a cell membrane is selectively permeable, what does this mean?

Accepted Answer

It allows some substances to pass while restricting others.

Question 13

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

Accepted Answer

DNA replication

Question 14

A cell uses a protein to move sodium ions from a low concentration inside the cell to a high concentration outside the cell. Which process is this?

Accepted Answer

Active transport

Question 15

Which of the following statements about diffusion is correct?

Accepted Answer

Diffusion is the movement of substances from high concentration to low concentration until equilibrium is reached.

Question 16

Which type of membrane transport is most important for the uptake of glucose into most animal cells?

Accepted Answer

Facilitated diffusion

Question 17

Which of the following best describes exocytosis?

Accepted Answer

A vesicle fuses with the plasma membrane to release its contents outside the cell.

Question 18

Which equation correctly represents the volume of a spherical cell?

Accepted Answer

$$V = \frac{4}{3} \pi r^3$

Question 19

Which of the following would most likely increase the rate of diffusion across a cell membrane?

Accepted Answer

Increasing the temperature.

Question 20

Which statement best explains why facilitated diffusion is necessary for some molecules?

Accepted Answer

Some molecules are too large or polar to pass through the hydrophobic core of the phospholipid bilayer.

Cell Membranes: Structure, Function, and Transport Mechanisms

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