Use the following information to answer the question below.
The figure illustrates the energy states associated with the
reaction A + B ↔ C + D. Which of the following represents the
activation energy required for the non-enzyme-catalyzed reaction in
the figure?
C
Use the following information to answer the question below.
The figure illustrates the energy states associated with the
reaction A + B ↔ C + D. Which of the following represents the
activation energy required for the enzyme-catalyzed reaction in the figure?
B
Use the following information to answer the question below.
The figure illustrates the energy states associated with the
reaction A + B ↔ C + D. Which of the following in the figure would be
the same in either an enzyme-catalyzed or a noncatalyzed reaction?
D
Use the following information to answer the question below.
The figure illustrates the energy states associated with the
reaction A + B ↔ C + D. Which of the following terms best describes
the forward reaction in the figure?
exergonic, ∆G < 0
Use the following information to answer the question below.
Activity of various enzymes at various temperatures (a) and at
various pH (b)
Which temperature and pH profile curves on the graphs are most
likely associated with an enzyme isolated from a human stomach where
conditions are strongly acid?
curves 1 and 4
Use the following information to answer the question below.
Activity of various enzymes at various temperatures (a) and at
various pH (b)
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?
curves 3 and 5
Use the following information to answer the question below.
Rate of an enzyme-catalyzed reaction as a function of varying
reactant concentration, with the concentration of enzyme constant
In the figure, why does the reaction rate plateau at higher
reactant concentrations?
Most enzyme molecules are occupied by substrate at high reactant concentrations.
Rate of an enzyme-catalyzed reaction as a function of varying
reactant concentration, with the concentration of enzyme constant.
For the enzyme-catalyzed reaction shown in the figure, if the
initial reactant concentration is 1.0 micromolar, which of these
treatments will cause the greatest increase in the rate of the reaction?
doubling the enzyme concentration
How might a change of one amino acid at a site, distant from the active site of an enzyme, alter the substrate specificity of an enzyme?
by changing the three-dimensional conformation of the enzyme
Which of the following graphs most likely describes the effect of pH on the function of the enzyme catalase in human cells? Note: The x-axis is pH and the y-axis is enzyme activity.
bell graph
How does a noncompetitive inhibitor decrease the rate of an enzyme-catalyzed reaction?
by binding to an allosteric site, thus changing the shape of the active site of the enzyme
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
Which of the following conditions may be overcome by increasing the substrate concentration in an enzymatic reaction with a fixed amount of enzyme?
competitive inhibition
Which of the following statements describes a key component of the induced fit hypothesis of enzyme catalysis?
Binding of substrate to the active site changes the shape of the active site of an enzyme.
Which of the following is a primary function of the active site of an enzyme?
It catalyzes the reaction associated with the enzyme.
During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?
-20 kcal/mol
What is the name of the thermodynamic barrier that must be overcome before products are formed in a spontaneous reaction?
activation energy
Which of the following characteristics is most likely to be associated with an enzyme that catalyzes two different chemical reactions?
Either the enzyme has two distinct active sites or the substrates involved in the two reactions have very similar structures.
Which of the following aspects of enzyme structure is best described by a clasping handshake analogy?
the specific manner in which an enzyme binds substrate
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.
Which of the following statements about enzyme function is true?
Enzymes increase the rate of chemical reactions by lowering activation energy barriers.
How do cells use the ATP cycle illustrated in the figure?
Cells use the cycle to recycle ADP and phosphate.
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.
A number of systems for pumping ions across membranes are powered by ATP. Such ATP-powered pumps are often called ATPases, although they do not often hydrolyze ATP unless they are simultaneously transporting ions. Because small increases in calcium ions in the cytosol can trigger a number of different intracellular reactions, cells keep the cytosolic calcium concentration quite low under normal conditions, using ATP-powered calcium pumps. For example, muscle cells transport calcium from the cytosol into the membranous system called the sarcoplasmic reticulum (SR). If a resting muscle cell's cytosol has a free calcium ion concentration of 10-7 while the concentration in the SR is 10-2, then how is the ATPase acting?
ATPase activity must be pumping calcium from the cytosol to the SR against the concentration gradient.
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.
When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is lost to the environment.
Which of the following statements describes a common characteristic of catabolic pathways?
They are exergonic and provide energy that can be used to produce ATP from ADP and i.
Which of the following molecules is most similar in structure to ATP?
an RNA nucleotide
Why is the ΔG of ATP hydrolysis in the cell about twice as great as the ΔG of ATP hydrolysis in a test tube under standard conditions?
Reactant and product concentrations in the test tube are different from those in the cell.
Which of the following statements describes a central role that ATP plays in cellular metabolism?
ATP provides energy coupling between exergonic and endergonic reactions.
Why do hydrolysis reactions occur more readily in solution than dehydration reactions?
Hydrolysis reactions are exergonic and increase entropy of the system.
The relationship between catabolism and anabolism is most similar to the relationship between which of the following pairs of terms?
exergonic; endergonic
Chemical equilibrium is relatively rare in living cells because metabolic pathways are interconnected. Which of the following statements describes an example of a reaction that may be at chemical equilibrium in a cell?
a chemical reaction in which neither the reactants nor the products are being produced or consumed in any metabolic pathway at that time in the cell
A chemical reaction that has a positive ΔG is best described as ________.
endergonic
Which of the following statements is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
Which of the following statements is true for a system at chemical equilibrium?
The system can do no work.
The mathematical expression for the change in free energy of a system is ΔG = ΔH - TΔS. Which of the following statements is correct?
ΔG is the change in free energy.
Which of the following statements about the evolution of life on Earth, from simple prokaryote-like cells to multicellular eukaryotic organisms, is true?
It has occurred in accordance with the laws of thermodynamics and resulted in a substantial decrease in the entropy of the planet.
Which of the following types of reactions would decrease the entropy within a cell?
anabolic reactions
Which of the following statements is consistent with the second law of thermodynamics?
A constant input of energy is required to maintain the high level of cellular organization.
Which of the following statements is a logical consequence of the second law of thermodynamics?
Each chemical reaction in an organism must increase the total entropy of the universe.
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?
The decrease in entropy is associated with growth of an organism. As a consequence of growth, organisms cause a greater increase in entropy in their environment than the decrease in entropy associated with their increased complexity.
Which of the following statements is an important consequence of the first law of thermodynamics for a living organism?
An organism ultimately must obtain all of the necessary energy for life from its environment.
Which of the following statements describes the first law of thermodynamics?
Energy cannot be created or destroyed.
Which of the following statements about anabolic pathways is true?
They consume energy to build up polymers from monomers.
Which of the following terms most precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism (catabolic pathways)
A decrease in entropy is associated with which type of reaction?
dehydration
Most cells cannot harness heat to perform work because ________.
temperature is usually uniform throughout a cell
Which of the following is an example of potential rather than kinetic energy?
a molecule of glucose
Which of the following statements is true of metabolism in its entirety in all organisms?
Metabolism consists of all the energy transformation reactions in an organism.