At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme?
answer
The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional
question
Which of the following statements about the active site of an enzyme is correct?
answer
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
question
Which of the following is true regarding metabolic pathways?
answer
Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.
question
Which of the following statements about enzyme function is correct?
answer
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.
question
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.
answer
allosteric regulation
question
Which of the following is changed by the presence of an enzyme in a reaction?
answer
The activation energy
question
If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
answer
Energy input into the organism must be occurring to drive the decrease in entropy.
question
The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling?
answer
Exergonic reactions drive endergonic reactions.
question
ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________.
answer
feedback inhibition
question
Which of the following statements about enzymes is true?
answer
Enzymes speed up the rate of the reaction without changing the ΞG for the reaction.
question
Which of these statements about enzyme inhibitors is true?
answer
The action of competitive inhibitors may be reversible or irreversible.
question
How does ATP drive transport work inside a cell?
answer
By phosphorylating a transport protein
question
How does ATP drive mechanical work inside a cell?
answer
By binding to motor proteins
question
Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?
answer
ATP can be regenerated by the addition of a phosphate group to ADP.
question
Which of the following reactions would be endergonic?
answer
Glucose + fructose β sucrose
question
Which of the following correctly states the relationship between anabolic and catabolic pathways?
answer
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
question
Enzyme activity is affected by pH because __________.
answer
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site
question
What best characterizes the role of ATP in cellular metabolism?
answer
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
question
Which of the following statements is correct regarding kinetic and potential energy?
answer
Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.
question
An exergonic (spontaneous) reaction is a chemical reaction that __________.
answer
releases energy when proceeding in the forward direction
question
Which of the following states the relevance of the first law of thermodynamics to biology?
answer
Energy can be freely transformed among different forms as long as the total energy is conserved.
question
Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?
answer
Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.
question
Which of the following statements is correct regarding ATP?
answer
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
question
What would the value of ΞS be for a chemical reaction in which a molecule is broken down into smaller components?
answer
Positive
question
Which of the following statements correctly describes cofactors and coenzymes?
answer
Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.
question
As ATP begins to build up in a cell, metabolism slows down. How does this happen?
answer
ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.
question
An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy.
answer
releases; absorbs
question
At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme?
answer
At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.
question
In general, the hydrolysis of ATP drives cellular work by __________.
answer
releasing free energy that can be coupled to other reactions
question
Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
answer
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
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