$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy} $$

Question 1

Which of the following best describes the Fluid Mosaic Model of the plasma membrane?

Accepted Answer

A dynamic structure where proteins are suspended in a fluid phospholipid bilayer, allowing lateral movement.

Question 2

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

Accepted Answer

The cell will swell and may burst because water enters the cell due to osmosis.

Question 3

Which of the following molecules can most easily diffuse across the plasma membrane without the help of a transport protein?

Accepted Answer

Oxygen (O\_2)

Question 4

What is the primary role of cholesterol in the plasma membrane?

Accepted Answer

To stiffen the membrane and reduce its fluidity at high temperatures.

Question 5

Which process requires energy input in the form of ATP to move substances across the plasma membrane?

Accepted Answer

Active transport

Question 6

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

Accepted Answer

It will undergo plasmolysis as water leaves the cell.

Question 7

Which of the following best explains why enzymes are highly specific in their action?

Accepted Answer

The active site of an enzyme has a unique shape that fits only specific substrates.

Question 8

Which statement about facilitated diffusion is correct?

Accepted Answer

It allows polar or charged substances to cross the membrane with the help of transport proteins.

Question 9

What is the main difference between competitive and noncompetitive enzyme inhibitors?

Accepted Answer

Competitive inhibitors bind to the enzyme's active site, while noncompetitive inhibitors bind elsewhere and change the enzyme's shape.

Question 10

Which equation correctly represents the hydrolysis of ATP to release energy?

Accepted Answer

$$ \mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy} $$

Question 11

A cell needs to import large quantities of cholesterol from the bloodstream. Which process is most likely used?

Accepted Answer

Receptor-mediated endocytosis

Question 12

Which of the following statements about energy transformations in cells is consistent with the second law of thermodynamics?

Accepted Answer

Some energy is lost as heat during energy conversions, increasing disorder.

Question 13

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway acts as an inhibitor of an enzyme early in the pathway.

Question 14

Which of the following is an example of mechanical work powered by ATP in cells?

Accepted Answer

Movement of a motor protein along a cytoskeletal filament

Question 15

Which of the following scenarios illustrates active transport?

Accepted Answer

Sodium ions being pumped from low to high concentration using ATP

Question 16

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

Accepted Answer

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

Question 17

Which of the following is true about exocytosis?

Accepted Answer

It involves the fusion of vesicles with the plasma membrane to release contents outside the cell.

Question 18

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

Accepted Answer

They allow rapid diffusion of water across the plasma membrane.

Question 19

Which of the following is a correct statement about the effect of enzymes on chemical reactions?

Accepted Answer

Enzymes decrease the activation energy, speeding up the reaction.

The Working Cell: Membrane Structure, Transport, and Energy

Study Guide - Practice Questions