Question 1

Which of the following best explains why the plasma membrane is described as a 'fluid mosaic'?

Accepted Answer

Because the membrane is a dynamic structure with various proteins and lipids that can move laterally within the bilayer.

Question 2

A researcher observes that a cell membrane becomes more rigid at lower temperatures. Which modification would most effectively increase membrane fluidity under these conditions?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in the phospholipids.

Question 3

Which of the following molecules can most easily diffuse across the plasma membrane without the aid of transport proteins?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

What is the primary function of glycoproteins and glycolipids on the extracellular surface of the plasma membrane?

Accepted Answer

Serving as molecular 'fingerprints' for cell-to-cell recognition.

Question 5

A red blood cell is placed in a hypotonic solution. What will most likely happen to the cell, and why?

Accepted Answer

It will swell and may burst because water moves into the cell.

Question 6

Which of the following best describes facilitated diffusion?

Accepted Answer

Movement of molecules down their concentration gradient with the help of transport proteins and without energy input.

Question 7

The sodium-potassium pump is an example of which of the following?

Accepted Answer

Active transport

Question 8

Which equation best represents the movement of sodium and potassium ions by the sodium-potassium pump?

Accepted Answer

$$2K^+_{(out)} + 3Na^+_{(in)} + ATP \rightarrow 2K^+_{(in)} + 3Na^+_{(out)} + ADP + P_i$$

Question 9

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the diffusion of water from a region of lower solute concentration to a region of higher solute concentration.

Question 10

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

Accepted Answer

The cell undergoes plasmolysis as water leaves the cell.

Question 11

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

Accepted Answer

It serves as a fluidity buffer, maintaining membrane fluidity across temperature changes.

Question 12

Which process requires energy input from the cell and moves substances against their concentration gradient?

Accepted Answer

Active transport

Question 13

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

Accepted Answer

Storage of genetic information

Question 14

A freshwater protist such as Paramecium uses a contractile vacuole to:

Accepted Answer

Expel excess water to maintain osmotic balance.

Question 15

Which of the following best describes cotransport?

Accepted Answer

The active transport of one solute directly coupled to the passive transport of another solute.

Question 16

Which of the following statements about bulk transport is correct?

Accepted Answer

Bulk transport involves the movement of large molecules via vesicles and requires energy.

Question 17

Which type of endocytosis is most specific for the uptake of particular molecules such as cholesterol via LDL particles?

Accepted Answer

Receptor-mediated endocytosis

Question 18

A cell has a membrane potential of $$-70\ \mathrm{mV}. $$What does this mean?

Accepted Answer

The inside of the cell is more negatively charged than the outside.

Question 19

Which of the following best explains why ions such as $$Na^+$$ and $$K^+$$ cannot freely diffuse across the plasma membrane?

Accepted Answer

They are hydrophilic and charged, so they cannot pass through the hydrophobic core of the membrane.

Question 20

Which of the following scenarios best illustrates the concept of an electrochemical gradient?

Accepted Answer

A difference in both ion concentration and charge across a membrane, such as more $$Na^+$$ outside and a negative charge inside.

Chapter 7

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