Chapter 8 (Intro to Metabolism)

Question 1

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Answer 1

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Question 2

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

Answer 2

Organisms acquire energy from and lose energy to their surroundings.

Question 3

Consider the growth of a farmer’s crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?

Answer 3

To obey the first law, the crops must represent an open system.

Question 4

Which of the following states the relevance of the first law of thermodynamics to biology?

Answer 4

Energy can be freely transformed among different forms as long as the total energy is conserved.

Question 5

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?

Answer 5

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

Question 6

According to the second law of thermodynamics, which of the following is true?

Answer 6

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

Question 7

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?

Answer 7

Energy input into the organism must be occurring to drive the decrease in entropy.

Question 8

Which part of the equation ΔG = ΔH – TΔS tells you if a process is spontaneous?

Answer 8

ΔG

Question 9

If, during a process, the system becomes more ordered, then __________.

Answer 9

ΔS is negative

Question 10

When one molecule is broken down into six component molecules, which of the following will always be true?

Answer 10

ΔS is positive.

Question 11

From the equation ΔG = ΔH – TΔS it is clear that __________.

Answer 11

a decrease in the system’s total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

Question 12

An exergonic (spontaneous) reaction is a chemical reaction that __________.

Answer 12

releases energy when proceeding in the forward direction

Question 13

Which of the following reactions would be endergonic?

Answer 13

glucose + fructose → sucrose

Question 14

Molecules A and B contain 110 kcal/mol of free energy, and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?

Answer 14

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.

Question 15

Which of the following determines the sign of ΔG for a reaction?

Answer 15

The free energy of the reactants and the free energy of the products

Question 16

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?

Answer 16

The continuous removal of the products of a pathway to be used in other reactions

An input of free energy from outside the pathway

Question 17

The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients?

Answer 17

Proton movement against a gradient of protons

Question 18

In general, the hydrolysis of ATP drives cellular work by __________.

Answer 18

releasing free energy that can be coupled to other reactions

Question 19

Enzyme activity is affected by pH because __________. (

Answer 19

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

Question 20

How do enzymes lower activation energy?

Answer 20

By locally concentrating the reactants

Question 21

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?

Answer 21

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction.

Question 22

Which of the following is changed by the presence of an enzyme in a reaction?

Answer 22

the potential energy of the products is less than the potential energy of the reactants

Question 23

Which of the following is changed by the presence of an enzyme in a reaction?

Answer 23

The activation energy

Question 24

Which of the following statements about enzymes is/are true?

Answer 24

Enzymes speed up the rate of the reaction without changing the DG for the reaction.

Question 25

Which of the following statements about enzyme function is correct?

Answer 25

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.