Question 1

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their double bonds create kinks, preventing tight packing of phospholipids.

Question 2

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 possibly burst because water will move into the cell by osmosis.

Question 3

Which of the following molecules would most easily diffuse through a pure phospholipid bilayer?

Accepted Answer

Oxygen ($$O_2)$$

Question 4

A cell is placed in a solution containing a high concentration of $$K^+$$ ions. The cell uses energy to pump $$K^+$$ into the cytoplasm, even though the concentration inside is already high. What type of transport is this?

Accepted Answer

Active transport

Question 5

Which of the following statements about the fluid mosaic model is correct?

Accepted Answer

Phospholipids and proteins can move laterally within the layer, contributing to membrane fluidity.

Question 6

Which factor would most likely decrease the permeability of a biological membrane to water?

Accepted Answer

Decreasing the temperature

Question 7

A scientist observes that a certain solute crosses the cell membrane only when a specific protein is present, and the process does not require ATP. Which transport mechanism is most likely involved?

Accepted Answer

Facilitated diffusion

Question 8

Which of the following best describes the relationship between membrane fluidity and temperature?

Accepted Answer

Membrane fluidity increases as temperature increases.

Question 9

If a cell membrane is composed primarily of saturated fatty acids, what effect would this have on the membrane's properties?

Accepted Answer

It would decrease membrane fluidity and permeability.

Question 10

Which of the following scenarios best illustrates secondary active transport?

Accepted Answer

A glucose molecule is transported into a cell against its concentration gradient by coupling to the movement of $$Na^+$$ down its gradient.

Question 11

Which of the following best explains why ions such as $$Na^+$$ and $$Cl^-$$ cannot easily cross the phospholipid bilayer?

Accepted Answer

They are hydrophilic and charged, so they are repelled by the hydrophobic core of the bilayer.

Question 12

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

Accepted Answer

It will shrink because water will move out of the cell.

Question 13

Which of the following is a key difference between simple diffusion and facilitated diffusion?

Accepted Answer

Facilitated diffusion requires a membrane protein, while simple diffusion does not.

Question 14

Which of the following best describes the role of cholesterol in animal cell membranes?

Accepted Answer

It stabilizes membrane fluidity across temperature changes.

Question 15

A patient is given an intravenous solution that is isotonic to their blood cells. What is the expected effect on the cells?

Accepted Answer

There will be no net movement of water, so the cells will remain unchanged.

Question 16

Which of the following best explains why the phospholipid bilayer forms spontaneously in water?

Accepted Answer

The hydrophilic heads interact with water, while the hydrophobic tails avoid water, leading to bilayer formation.

Question 17

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

Accepted Answer

Increasing the temperature

Question 18

A cell is observed to take in large particles by engulfing them with its membrane, forming a vesicle. What is this process called?

Accepted Answer

Phagocytosis

Question 19

Which of the following best describes the relationship between membrane permeability and membrane fluidity?

Accepted Answer

As membrane fluidity increases, permeability generally increases.

Question 20

Which of the following is true regarding the movement of water across cell membranes?

Accepted Answer

Water can move through the membrane via simple diffusion or through aquaporin channels.

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