Midterm Metabolism
The ∆G for a particular enzyme-catalyzed reaction is -20 kcal/mol. If the amount of enzyme in the reaction is doubled, what will be the ∆G for the new reaction?
-20 kcal/mol
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.
Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their growth.
Which of the following is a statement of the first law of thermodynamics?
Energy cannot be created or destroyed.
Which of the following statements regarding enzymes is true?
Enzymes increase the rate of a reaction by lowering the activation energy barrier.
Which of the following is true of enzymes?
Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
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.
Hydrolysis of ATP releases energy, which results in the production of ADP and inorganic phosphate. What is commonly the ultimate fate of inorganic phosphate produced in the cytosol?
It is combined with ADP to regenerate ATP.
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.
Which of the following is true for anabolic pathways?
They consume energy to build polymers from monomers.
Which of the following statements concerning catabolic pathways is true?
They provide energy that can be used to drive cellular work.`
Which of the following is true of metabolism in its entirety in all organisms?
Which of the following is true of metabolism in its entirety in all organisms?
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
In most exergonic reactions, the reactants capable of interacting to form products typically must first overcome a thermodynamic barrier known as the:
activation energy of the reaction.
Which of the following types of reactions would decrease the entropy within a cell?
anabolic reactions
The cellular process of synthesizing large molecules from smaller ones is defined as:
anabolism
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
A noncompetitive inhibitor decreases the rate of an enzymatic reaction by:
changing the shape of the enzyme active site.
Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n):
cofactor necessary for enzyme activity.
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
For the enzyme-catalyzed reaction shown in Figure 6.2, which of these treatments will cause the greatest increase in the rate of the reaction if the initial reactant concentration is 1.0 micromolar?
doubling the enzyme concentration
A chemical reaction that has a positive ΔG is best described as:
endergonic.
Energy transformations are always associated with an increase in the
entropy of the universe
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.
Which of the following is an exergonic reaction?
hydrolysis of glycogen to release glucose monomers
Which of the following tend(s) to release energy?
hydrolysis reactions
Under a particular set of conditions in the lab, the enzyme in a chemical reaction is saturated. Which of the following alterations to the reaction will increase the rate at which substrate is converted to product?
increasing the amount of enzyme in the reaction
A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because:
the starch solution has less free energy than the sugar solution.