Question 1

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

Accepted Answer

A double layer of phospholipids with proteins and other molecules embedded throughout, allowing lateral movement.

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which type of solution was the cell placed in?

Accepted Answer

Hypotonic

Question 3

Which of the following is a function of membrane proteins?

Accepted Answer

Facilitating the movement of specific molecules across the membrane

Question 4

What is the main difference between passive and active transport across cell membranes?

Accepted Answer

Passive transport moves substances down their concentration gradient without energy input, while active transport requires energy to move substances against their gradient.

Question 5

A freshwater Paramecium uses contractile vacuoles to expel water. This is necessary because:

Accepted Answer

The cytoplasm is hypertonic to the surrounding water, causing water to enter the cell by osmosis.

Question 6

Which of the following best explains why phospholipids form bilayers in water?

Accepted Answer

Their hydrophobic tails avoid water while their hydrophilic heads interact with water.

Question 7

Which process describes the movement of water across a selectively permeable membrane?

Accepted Answer

Osmosis

Question 8

A cell actively transports $$\mathrm{Ca$$^{2+}$$}$$ ions out of the cytoplasm. What does this indicate about the concentration of $$\mathrm{Ca$$^{2+}$$}$$?

Accepted Answer

It is higher outside the cell than inside.

Question 9

Which of the following is an example of exocytosis?

Accepted Answer

A neuron releasing neurotransmitters into a synapse.

Question 10

Which statement about the second law of thermodynamics is correct in the context of biological systems?

Accepted Answer

Energy transfers or transformations increase disorder (entropy), with some energy lost as heat.

Question 11

Which of the following best describes an exergonic reaction?

Accepted Answer

A reaction that releases energy and yields products with less potential energy than the reactants.

Question 12

How does ATP transfer energy to drive cellular work?

Accepted Answer

By transferring a phosphate group to another molecule, making it more reactive.

Question 13

Which of the following statements about enzymes is true?

Accepted Answer

Enzymes lower the activation energy needed for a reaction to proceed.

Question 14

A competitive inhibitor affects an enzyme by:

Accepted Answer

Blocking the active site so the substrate cannot bind.

Question 15

Which of the following is an advantage of feedback inhibition in metabolic pathways?

Accepted Answer

It prevents the overproduction of the end product, conserving resources.

Question 16

Which of the following best explains why facilitated diffusion does not require energy?

Accepted Answer

It moves substances down their concentration gradient with the help of transport proteins.

Question 17

Which of the following scenarios is an example of receptor-mediated endocytosis?

Accepted Answer

A cell taking in specific molecules after they bind to receptors on the cell surface.

Question 18

Which of the following best describes the role of aquaporins in cells?

Accepted Answer

They allow rapid diffusion of water across the cell membrane.

Question 19

A scientist discovers a new drug that binds irreversibly to the active site of an enzyme. What is the likely effect of this drug?

Accepted Answer

It will permanently inactivate the enzyme, preventing substrate binding.

Question 20

Which of the following best explains why diffusion of a solute across a membrane increases entropy?

Accepted Answer

It results in a more random distribution of molecules, increasing disorder.

Chapter 5: The Working Cell – Membrane Structure, Function, and Cellular Energy

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