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CHAP 8 MULTIPLE CHOICE
Terms in this set (36)
Which of the following is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
Chemical equilibrium is relatively rare in living cells. An example of a reaction at chemical equilibrium in a cell would be _____.
a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _____ is to _____.
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
Which of the following is most similar in structure to ATP?
Catabolic pathways _____.
supply energy, primarily in the form of ATP, for the cell's work
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
it lost to the environment
When ATP releases some energy, it also releases inorganic phosphate. What happens to the inorganic phosphate in the cell?
It may be used to form a phosphorylated intermediate.
Which of the following is the most correct interpretation of the figure?
ATP is a molecule that acts as an intermediary to store energy for cellular work.
How do cells use the ATP cycle shown in the figure?
Cells use the cycle to recycle ADP and phosphate.
Which of the following is true of enzymes?
Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
Which of the following is true when comparing an uncatalyzed reaction to the same reaction with a catalyst?
The catalyzed reaction will have the same ∆G.
The lock-and-key analogy for enzymes applies to the specificity of enzymes _____.
binding to their substrate
You have discovered an enzyme that can catalyze two different chemical reactions. Which of the following is most likely to be correct?
Either the enzyme has two distinct active sites or the reactants involved in the two reactions are very similar in size and shape.
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's _____.
The active site of an enzyme is the region that _____.
is involved in the catalytic reaction of the enzyme
According to the induced fit hypothesis of enzyme catalysis,
the binding of the substrate changes the shape of the enzyme's active site
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
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 cofactor necessary for enzyme activity
A noncompetitive inhibitor decreases the rate of an enzyme reaction by _____.
changing the shape of the enzyme active site
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter an enzyme's substrate specificity?
change in enzyme shape
Which curves on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?
3 and 5
Which temperature and pH profile curves on the graphs were most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid?
1 and 4`
Which of the following in the figure would be the same in either an enzyme-catalyzed or a noncatalyzed reaction?
Which of the following represents the activation energy required for the enzyme-catalyzed reaction in the figure?
Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
HIV is the virus that causes AIDS. In the mid-1990s, researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it. If this strategy for stopping HIV infections were successful, it would be an example of what phenomenon?
A series of enzymes catalyze the reaction 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.
With respect to the enzyme that converts X to Y, substance A functions as _____.
an allosteric inhibitor
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as _____.
You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites. One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein?
It is probably an enzyme that works through allosteric regulation.
Allosteric enzyme regulation is usually associated with _____.
an enzyme with more than one subunit
Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
localization of enzymes into specific organelles or membranes
Anabolic pathways _____.
consume energy to build up polymers
Which of the following is a statement of the first law of thermodynamics?
energy cannot be created destroyed
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.
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