Q: A reaction in a cell has $$\Delta H = -50 kJ/$$mol and $$\Delta S = +0.1 kJ/($$mol\cdot K)$$. At T = 300$ K, what is $$\Delta G$ for this reaction?

$$\Delta G = -50 - (300 \times 0.1) = -80 kJ/$$mol

Question 1

Which of the following best explains why an electrolyte mix containing glucose and sodium (such as Liquid IV) hydrates cells more efficiently than water alone?

Accepted Answer

Glucose and sodium increase the osmotic gradient, promoting water movement into cells via secondary active transport.

Question 2

According to the first law of thermodynamics, which statement is correct regarding energy in biological systems?

Accepted Answer

Energy can be converted between forms, but the total amount of energy in a closed system remains constant.

Question 3

Which equation correctly represents Gibbs Free Energy and its components?

Accepted Answer

$$\Delta G = \Delta H - T \Delta S$$

Question 4

A reaction in a cell has $$\Delta H = -50 kJ/$$mol and $$\Delta S = +0.1 kJ/($$mol\cdot K)$$. At T = 300$ K, what is $$\Delta G$ for this reaction?

Accepted Answer

$$\Delta G = -50 - (300 	imes 0.1) = -80 kJ/$$mol

Question 5

Which statement best describes a spontaneous reaction in biological systems?

Accepted Answer

A reaction with $$\Delta G \u003c 0$$ that can occur without external energy input, given sufficient time.

Question 6

Why do spontaneous reactions in cells sometimes proceed very slowly, despite having a negative $$\Delta G$$?

Accepted Answer

They require overcoming a high activation energy barrier before products can form.

Question 7

What is the primary role of enzymes in biological reactions?

Accepted Answer

Enzymes lower the activation energy required for a reaction, increasing the reaction rate.

Question 8

Which of the following best describes how ATP hydrolysis is used to drive energetically unfavorable reactions in cells?

Accepted Answer

ATP hydrolysis ($$\Delta G = -30.5 kJ/$$mol) is coupled to unfavorable reactions, making the overall $$\Delta G$$ negative.

Question 9

A cell needs to synthesize sucrose from glucose and fructose, but the reaction is not spontaneous. How does the cell accomplish this?

Accepted Answer

By coupling the reaction to ATP hydrolysis, which provides the necessary free energy.

Question 10

Which of the following is true about the second law of thermodynamics in biological systems?

Accepted Answer

Biological systems maintain order by increasing the disorder (entropy) of their surroundings.

Question 11

What is the function of activated carriers such as ATP in cellular metabolism?

Accepted Answer

They transfer energy from favorable to unfavorable reactions, allowing both to proceed.

Question 12

Which process is illustrated by water moving into cells due to a higher concentration of sodium and glucose inside the cell?

Accepted Answer

Osmosis driven by an osmotic gradient.

Question 13

If a reaction has a large negative $$\Delta G$$ but does not occur rapidly, what is the most likely explanation?

Accepted Answer

The activation energy barrier is high, slowing the reaction rate.

Question 14

Which of the following best describes the transition state in a chemical reaction?

Accepted Answer

A temporary, high-energy state that reactants must reach before forming products.

Question 15

In the context of enzyme catalysis, what is meant by 'lowering the activation energy'?

Accepted Answer

Enzymes stabilize the transition state, making it easier for reactants to convert to products.

Question 16

Which of the following is NOT a property of enzymes?

Accepted Answer

Enzymes are consumed during the reaction and cannot be reused.

Question 17

A cell couples the hydrolysis of ATP ($$\Delta G = -30.5 kJ/$$mol) to a reaction with $$\Delta G = +20 kJ/$$mol. What is the net $$\Delta G of $$the coupled reaction?

Accepted Answer

$$\Delta G_{net} = -30.5 + 20 = -10.5 kJ/$$mol

Question 18

Which of the following scenarios best illustrates the concept of coupling in cellular metabolism?

Accepted Answer

Using ATP hydrolysis to drive the synthesis of sucrose from glucose and fructose.

Question 19

Which statement about the relationship between entropy and biological order is correct?

Accepted Answer

Cells maintain internal order by increasing the entropy of their environment.

Question 20

Which of the following is a real-life example of secondary active transport in human physiology?

Accepted Answer

Sodium-glucose cotransport in the intestinal epithelium.

Plasma Membrane, Thermodynamics, and Energetics in Biology

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