Question 1

Which of the following best describes the structure of the plasma membrane in eukaryotic cells?

Accepted Answer

A phospholipid bilayer with embedded proteins

Question 2

Phospholipids in the plasma membrane are described as amphipathic. What does this mean?

Accepted Answer

They contain both hydrophilic and hydrophobic regions

Question 3

Which type of molecule can most easily diffuse across the phospholipid bilayer of the plasma membrane without the help of a transport protein?

Accepted Answer

Small non-polar molecules

Question 4

The plasma membrane is described as 'selectively permeable.' Which feature of phospholipids is most responsible for this property?

Accepted Answer

The amphipathic nature, with hydrophilic heads and hydrophobic tails

Question 5

A cell is placed in a hypertonic solution. What is the most likely outcome for the cell?

Accepted Answer

It will lose water and shrink

Question 6

Which equation best represents the movement of water during osmosis across a cell membrane?

Accepted Answer

$$H_2O$$ moves from an area of high $$[H_2O] to $$low $$[H_2O]$$ across the membrane

Question 7

Which of the following statements about membrane fluidity is correct?

Accepted Answer

Membrane fluidity increases with more unsaturated fatty acids

Question 8

What is the primary function of proteins embedded in the plasma membrane?

Accepted Answer

To regulate the entry and exit of substances

Question 9

Which of the following best explains why ions cannot easily cross the phospholipid bilayer?

Accepted Answer

Ions are repelled by the hydrophobic core of the bilayer

Question 10

A patient is given an intravenous solution that is hypotonic compared to their blood plasma. What is the most likely effect on their red blood cells?

Accepted Answer

The cells will swell and may burst (lyse)

Question 11

Which of the following transport processes requires energy input from the cell?

Accepted Answer

Active transport

Question 12

Which protein is responsible for transporting water molecules across the plasma membrane?

Accepted Answer

Aquaporin

Question 13

If a cell membrane becomes too solid, which of the following is most likely to occur?

Accepted Answer

The membrane will become rigid and may shatter

Question 14

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

Accepted Answer

A dynamic bilayer of phospholipids with proteins floating within it

Question 15

Which of the following would increase the risk of a cell membrane freezing at low temperatures?

Accepted Answer

Increasing the proportion of saturated fatty acids

Question 16

Which equation best describes the net movement of a solute during passive diffusion across the plasma membrane?

Accepted Answer

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

Question 17

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

Accepted Answer

Synthesizing DNA

Question 18

Facilitated diffusion differs from simple diffusion in that:

Accepted Answer

Facilitated diffusion uses membrane proteins to transport substances

Question 19

Which of the following best explains why glucose requires a transporter to cross the plasma membrane?

Accepted Answer

Glucose is a large polar molecule

Question 20

A cell is placed in an isotonic solution. What will happen to the movement of water across its plasma membrane?

Accepted Answer

Water will move equally in both directions, with no net change

The Plasma (Cell) Membrane: Structure, Function, and Permeability

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