Question 1

Which property of phospholipids is primarily responsible for the spontaneous formation of the cell membrane bilayer in aqueous environments?

Accepted Answer

Their amphipathic nature, having both hydrophilic heads and hydrophobic tails

Question 2

The 'fluid mosaic model' of the cell membrane describes:

Accepted Answer

A dynamic structure with proteins and lipids moving laterally within the bilayer

Question 3

Which of the following would most likely increase the fluidity of a cell membrane at low temperatures?

Accepted Answer

Increasing the proportion of unsaturated phospholipids

Question 4

A membrane protein is found to span the entire lipid bilayer and has hydrophobic amino acids in the middle of its structure. What type of protein is this most likely to be?

Accepted Answer

An integral (transmembrane) protein

Question 5

Which of the following molecules can most easily diffuse across a pure phospholipid bilayer without the aid of a transport protein?

Accepted Answer

Oxygen ($O_2$)

Question 6

What is the main difference between simple diffusion and facilitated diffusion across a cell membrane?

Accepted Answer

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

Question 7

Which direction do water molecules move during osmosis, and under what conditions?

Accepted Answer

From areas of low solute concentration to areas of high solute concentration

Question 8

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

Accepted Answer

It will swell and may burst due to water entering the cell by osmosis

Question 9

Which of the following best describes the role of the sodium-potassium pump ($Na^+/K^+$ ATPase) in animal cells?

Accepted Answer

It uses ATP to move $Na^+$ out of the cell and $K^+$ into the cell, maintaining an electrochemical gradient

Question 10

Which of the following is an example of secondary active transport?

Accepted Answer

The use of a sodium gradient to drive glucose uptake via a symporter

Question 11

Why do cells benefit from gating their membrane channels?

Accepted Answer

To regulate the flow of ions and molecules, maintaining homeostasis and responding to signals

Question 12

Which of the following best explains why glucose cannot cross the cell membrane by simple diffusion?

Accepted Answer

Glucose is large and polar, so it requires a transport protein to cross the hydrophobic core of the membrane

Question 13

What is the main source of energy for primary active transport in cells?

Accepted Answer

Hydrolysis of ATP

Question 14

A cell is placed in a solution with a higher concentration of solutes than inside the cell. What type of solution is this, and what will happen to the cell?

Accepted Answer

Hypertonic; the cell will lose water and shrink

Question 15

Which of the following best describes the function of aquaporins in the cell membrane?

Accepted Answer

They facilitate the rapid movement of water molecules across the membrane

Question 16

Which process do eukaryotic cells use to move large molecules, such as proteins, out of the cell?

Accepted Answer

Exocytosis

Question 17

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

Accepted Answer

The cells will swell and may burst due to water influx

Question 18

Which of the following best explains why the sodium-potassium pump is necessary for nerve cell function?

Accepted Answer

It maintains the electrochemical gradient required for action potentials

Question 19

Which of the following statements about co-transport (secondary active transport) is correct?

Accepted Answer

It uses the energy stored in an ion gradient established by primary active transport to move another substance against its gradient

Question 20

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

Accepted Answer

It helps maintain membrane fluidity at different temperatures

Cell Membrane Structure and Transport Mechanisms

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