Question 1

Which statement best describes the first law of thermodynamics as it applies to living organisms?

Accepted Answer

Energy can be transferred or transformed, but cannot be created or destroyed.

Question 2

A cell uses ATP to drive the synthesis of a protein from amino acids. Which type of metabolic pathway is this an example of?

Accepted Answer

Biosynthetic (anabolic) pathway

Question 3

Which of the following equations correctly represents the change in free energy ($$\Delta G) $$for a chemical reaction?

Accepted Answer

$$\Delta G = G_{final} - G_{initial}$$

Question 4

During cellular respiration, glucose is broken down and energy is released. Which type of reaction is this, and what is the sign of $$\Delta G$$?

Accepted Answer

Exergonic reaction; $$\Delta G is $$negative

Question 5

Why do cells avoid reaching equilibrium in their metabolic pathways?

Accepted Answer

At equilibrium, no work can be performed and metabolism would stop.

Question 6

Which of the following best explains how ATP hydrolysis powers cellular work?

Accepted Answer

ATP hydrolysis releases energy by breaking the bonds between phosphate groups, which is used to phosphorylate other molecules.

Question 7

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Competing with the substrate for binding at the active site.

Question 8

Which of the following is NOT a way that enzymes lower the activation energy ($$E_a) of a $$reaction?

Accepted Answer

Increasing the free energy ($$\Delta G) of $$the reaction

Question 9

A patient is given a drug that acts as a noncompetitive inhibitor for a key metabolic enzyme. What is the most likely effect?

Accepted Answer

The drug will bind to a separate site, causing the enzyme to change shape and become less effective.

Question 10

Which statement about feedback inhibition is correct?

Accepted Answer

It prevents a cell from wasting resources by shutting down a pathway when the end product is abundant.

Question 11

Which of the following best describes the role of cofactors in enzyme activity?

Accepted Answer

Cofactors are nonprotein molecules that assist enzymes in catalyzing reactions.

Question 12

A hydroelectric dam is used as an analogy for cellular metabolism. What does the flow of water through the dam represent in terms of cellular processes?

Accepted Answer

The flow of water represents the constant flow of materials and energy through open systems like cells.

Question 13

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

Accepted Answer

Every energy transfer or transformation increases the entropy (disorder) of the universe.

Question 14

Which of the following best explains why enzymes are necessary for life?

Accepted Answer

Enzymes lower the activation energy ($$E_a) of $$reactions, allowing them to occur at moderate temperatures.

Question 15

Which of the following is a correct statement about the ATP cycle in cells?

Accepted Answer

ATP is regenerated by the addition of a phosphate group to ADP, using energy from catabolic reactions.

Question 16

A scientist increases the substrate concentration in an enzyme-catalyzed reaction. What will happen when all enzyme molecules are saturated with substrate?

Accepted Answer

The reaction rate will plateau, and can only be increased by adding more enzyme.

Question 17

Which of the following is an example of allosteric regulation?

Accepted Answer

A regulatory molecule binds to a site other than the active site, stabilizing the enzyme's active or inactive form.

Question 18

Which of the following best describes the induced fit model of enzyme activity?

Accepted Answer

The enzyme changes shape slightly to fit the substrate, bringing chemical groups together for catalysis.

Question 19

Which of the following reactions is an example of an endergonic process in living cells?

Accepted Answer

Photosynthesis: $$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6$ + 6O_2$$

Chapter 6: An Introduction to Metabolism – Study Notes

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