Question 1

Which equation correctly describes the Gibbs Free Energy change ($\Delta G_{transport}$) for the diffusion of an uncharged solute across a membrane?

Accepted Answer

$\Delta G_{transport} = RT \ln \left( \frac{C_{final}}{C_{initial}} \right)$

Question 2

A cell has an extracellular glucose concentration of 5 mM and an intracellular concentration of 0.5 mM at 25°C. Calculate $\Delta G_{transport}$ for glucose diffusion from outside to inside the cell. ($R = 8.315$ J/mol·K, $T = 298$ K)

Accepted Answer

$-3.98$ kJ/mol

Question 3

If $\Delta G_{transport}$ for a solute is negative, what does this indicate about the process?

Accepted Answer

The process is spontaneous and exergonic.

Question 4

Given $C_{outside} = 1$ M and $C_{inside} = 0.01$ M for glucose at 25°C, what is $\Delta G_{transport}$ for diffusion from inside to outside?

Accepted Answer

$+11.5$ kJ/mol

Question 5

Which of the following best describes the effect of increasing the concentration gradient on $\Delta G_{transport}$ for an uncharged solute?

Accepted Answer

$\Delta G_{transport}$ becomes more negative as the gradient increases.

Question 6

A researcher wants to pump an uncharged solute against a 10-fold concentration gradient at 25°C. What is the minimum energy cost ($\Delta G_{transport}$) required?

Accepted Answer

$+5.7$ kJ/mol

Question 7

Which of the following scenarios would result in a positive $\Delta G_{transport}$ for an uncharged solute?

Accepted Answer

Transport from low to high concentration.

Question 8

If the temperature increases, what is the effect on $\Delta G_{transport}$ for a given concentration gradient?

Accepted Answer

$\Delta G_{transport}$ increases in magnitude (more positive or negative depending on direction).

Question 9

Which of the following best explains why the diffusion of glucose from outside to inside a cell with $C_{outside} > C_{inside}$ is spontaneous?

Accepted Answer

The process moves down the concentration gradient, resulting in a negative $\Delta G_{transport}$.

Question 10

A cell is placed in a solution where $C_{outside} = C_{inside}$. What is the value of $\Delta G_{transport}$ for an uncharged solute?

Accepted Answer

$0$ kJ/mol

Question 11

Which of the following is NOT a factor in the calculation of $\Delta G_{transport}$ for an uncharged solute?

Accepted Answer

The electrical potential across the membrane.

Question 12

If $\Delta G_{transport}$ is calculated to be $+5.7$ kJ/mol for a process, what does this imply about the direction of solute movement?

Accepted Answer

The solute is being moved against its concentration gradient.

Question 13

Which of the following best describes the relationship between $\Delta G_{transport}$ and the spontaneity of membrane diffusion?

Accepted Answer

A negative $\Delta G_{transport}$ indicates a spontaneous process.

Question 14

A scientist observes that $\Delta G_{transport}$ for a certain solute is zero. What can be concluded about the concentrations of the solute on both sides of the membrane?

Accepted Answer

The concentrations are equal.

Thermodynamics of Membrane Diffusion: Uncharged Molecules

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