BIO 111 Chapter 6 Homework

Which of the following statements concerning catabolic pathways is true?

They provide energy that can be used to drive cellular work.

The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of

a catabolic pathway

Which of the following is an example of potential rather than kinetic energy?

a molecule of glucose

For the hydrolysis of ATP to ADP + i, the free-energy change is -7.3 kcal/mol under standard conditions (1 M concentration of both reactants and products). In the cellular environment, however, the free-energy change is about -13 kcal/mol. What can we conclude about the free-energy change for the formation of ATP from ADP and i under cellular conditions?

It is about +13 kcal/mol.

Which of the following statements about enzyme-catalyzed reactions is true?

The rate of the reaction is greater than when the same reaction occurs in the absence of an enzyme.

Which of the following is true for all exergonic reactions?

The reaction proceeds with a net release of free energy

What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?

There is no difference.

ATP hydrolysis in a test tube releases only about half as much energy as ATP hydrolysis in the cell. Which of the following is the best explanation for this observation?

ATP hydrolysis in a test tube occurs under standard conditions; in the cell, reactant and product concentrations differ from standard conditions

Which of the following describes the critical role that ATP plays in cellular metabolism?

ATP serves as an energy shuttle in the cell, coupling exergonic and endergonic reactions.

Which of the following represents the activation energy required for the enzyme-catalyzed reaction in the figure?

B

Which of the following represents the activation energy required for a non-catalyzed reaction in the figure?

C

Which of the following represents the ΔG of the reaction in the figure?

D

What is true about enzymes?

Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

A series of enzymes catalyze the reactions illustrated in the following metabolic pathway: X → Y → Z → A. Product A binds to the enzyme that converts X to Y at a position remote from its active site. This binding decreases the activity of the enzyme. What is substance X?

a substrate

Give an example of cooperativity

binding of a molecule to one subunit of a tetramer, which promotes faster binding to each of the other three subunits

The active site of an enzyme is the region that

binds substrates for the enzyme.

The cellular process of breaking down large molecules into smaller ones is defined as

catabolism

Which temperature and pH profile curves on the graphs in the figure were most likely generated from analysis of an enzyme from a human stomach, where conditions are strongly acid?

curves 1 and 4

Which curves on the graphs in the figure may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot spring at temperatures of 70°C or higher?

curves 3 and 5

Which of the following reactions tend to require an input of energy?

dehydration

Which of the following is a statement of the first law of thermodynamics?

energy cannot be created or destroyed

Energy transformations are always associated with an increase in the

entropy of the universe

The mechanism by which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

feedback inhibition

Enzymes are described as catalysts, which means that they

increase the rate of a reaction without being consumed by the reaction

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

the activation energy barrier for this reaction cannot easily be surmounted at room temperature.