Question 1

Which of the following best describes the relationship between the second law of thermodynamics and diffusion across a membrane?

Accepted Answer

Diffusion moves particles from high to low concentration, increasing entropy.

Question 2

A cell needs to move glucose (a polar molecule) from a region of low concentration outside the cell to a region of high concentration inside the cell. Which process will the cell most likely use?

Accepted Answer

Active transport using a membrane pump and ATP

Question 3

Which of the following is a direct consequence of the first law of thermodynamics in biological systems?

Accepted Answer

Energy can be transformed from chemical to mechanical forms, but not created or destroyed.

Question 4

ATP hydrolysis is often coupled to unfavorable reactions in cells. Which equation best represents the hydrolysis of ATP?

Accepted Answer

$$ \mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} $$

Question 5

Which of the following molecules is most likely to diffuse freely across a phospholipid bilayer without the help of a protein?

Accepted Answer

Cortisol (a nonpolar steroid hormone)

Question 6

A neuron spends a significant portion of its energy maintaining a sodium (Na+) and potassium (K+) gradient. What is the main reason for this energy expenditure?

Accepted Answer

To allow rapid changes in membrane potential for signaling

Question 7

Which of the following statements about dynamic equilibrium is correct?

Accepted Answer

At dynamic equilibrium, there is no net movement of molecules, but individual molecules continue to move.

Question 8

Which process is an example of a non-spontaneous reaction in cells that requires energy input?

Accepted Answer

Movement of potassium ions (K+) out of the cell via the sodium-potassium pump

Question 9

Which of the following best explains why the sodium-potassium pump is essential for neuron function?

Accepted Answer

It allows neurons to maintain a negative charge inside the cell, enabling action potentials.

Question 10

Which of the following is true about passive transport?

Accepted Answer

It moves molecules down their concentration gradient without energy input.

Question 11

A scientist observes that a cell is moving chloride ions (Cl-) into the cell against their concentration gradient. Which mechanism is most likely responsible?

Accepted Answer

Active transport using a symporter coupled to potassium movement

Question 12

Which of the following best describes the energy changes when a cell moves sodium ions (Na+) from low to high concentration across a membrane?

Accepted Answer

The process is non-spontaneous and requires energy input, usually from ATP.

Question 13

Which of the following is NOT a critical function of ATP in the cell?

Accepted Answer

Serving as a building block for DNA synthesis

Question 14

Which of the following best explains why phospholipid bilayers are important for creating concentration gradients in cells?

Accepted Answer

They allow selective permeability, enabling cells to maintain different concentrations of solutes inside and outside.

Question 15

Which of the following is an example of coupling a non-spontaneous reaction to a spontaneous one in cells?

Accepted Answer

Using ATP hydrolysis to drive the synthesis of macromolecules

Question 16

A cell is placed in a solution where the concentration of solute is equal inside and outside the cell. What will happen to the movement of solute molecules?

Accepted Answer

There will be no net movement, but molecules will continue to move in both directions.

Question 17

Which of the following best describes the role of thermal energy in diffusion?

Accepted Answer

Thermal energy causes particles to move randomly, enabling diffusion.

Question 18

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It requires energy from ATP to move ions against their gradients.

Question 19

Which of the following is a consequence of the second law of thermodynamics for living organisms?

Accepted Answer

Living organisms can decrease entropy in their local environment by using energy.

Question 20

Which of the following best describes the movement of ions through a ligand-gated channel after acetylcholine binds?

Accepted Answer

Ions move down their concentration gradient, resulting in a change in membrane potential.

Thermodynamics and Concentration Gradients in Cellular Biology

Study Guide - Practice Questions

Study Guide - Flashcards