BIOL 1201 Chapter 8
An enzyme is consumed during the reaction it catalyzes
Which of the following statements about enzymes is INCORRECT?
the potential energy of the products is less than the potential energy of the reactants
A chemical reaction is designated as exergonic rather than endergonic when __________.
there is too little activation energy available
A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________.
exergonic
A(n) _____ reaction occurs spontaneously.
feedback inhibition
ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________.
The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.
According to the second law of thermodynamics, which of the following is true?
releases energy when proceeding in the forward direction
An exergonic (spontaneous) reaction is a chemical reaction that __________.
releases; absorbs
An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy.
ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.
As ATP begins to build up in a cell, metabolism slows down. How does this happen?
The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.
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?
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.
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?
ATP can be regenerated by the addition of a phosphate group to ADP.
Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible?
potential
Chemical energy is a form of _____ energy.
exergonic; endergonic
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _______ is to _______.
To obey the first law, the crops must represent an open system
Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics?
the covalent bonds of a sugar molecule: potential energy
Energy is observed in two basic forms: potential and kinetic. Which of the following correctly matches these forms with a source of energy?
high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site
Enzyme activity is affected by pH because __________.
increase the rate of a reaction without being consumed by the reaction
Enzymes are described as catalysts, which means that they _____.
a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change
From the equation ΔG = ΔH - TΔS it is clear that __________.
by locally concentrating the reactants
How do enzymes lower activation energy?
By binding to motor proteins
How does ATP drive mechanical work inside a cell?
By phosphorylating a transport protein
How does ATP drive transport work inside a cell?
by changing the shape of the enzyme's active site
How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes
How does an enzyme increase the rate of the chemical reaction it catalyzes?
Nothing; the reaction will stay at equilibrium
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
Energy input into the organism must be occurring to drive the decrease in entropy.
If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously?
ΔS is negative
If, during a process, the system becomes more ordered, then __________.
ATP
In cells, what is usually the immediate source of energy for an endergonic reaction?
releasing free energy that can be coupled to other reactions
In general, the hydrolysis of ATP drives cellular work by __________.
cellular respiration
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
The first and second listed responses are correct.
Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium?
The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.
Molecules A and B contain 110 kcal/mol of free energy, and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded?
temperature is usually uniform throughout a cell.
Most cells cannot harness heat to perform work because
Organisms acquire energy from, and lose energy to, their surroundings
Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description
exergonic ....... uphill
Select the INCORRECT association
their enzymes have high optimal temperatures
Some bacteria are metabolically active in hot springs because
Succinylcholine must be a competitive inhibitor with acetylcholine
Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation?
is involved in the catalytic reaction of the enzyme.
The active site of an enzyme is the region that
The compound is a competitive inhibitor
The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?
The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.
The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs?
exergonic
The energy for an endergonic reaction comes from a(n) _____ reaction
the hydrolysis of ATP
The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways?
proton movement against a gradient of protons
The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients?
Exergonic reactions drive endergonic reactions.
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?
a catabolic pathway
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of _____.
allosteric regulation
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________.
allosteric activation
The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of __________.
endergonic
The reaction ADP + P --> ATP is a(n) _____ reaction
The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.
What best characterizes the role of ATP in cellular metabolism?
Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction.
What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction?
The enzyme changes its shape slightly as the substrate binds to it.
What is meant by the "induced fit" of an enzyme?
It is acquired by a reactant in an endergonic reaction
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
The free-energy change (ΔG) of the hydrolysis of ATP to ADP and Pi may vary considerably with variations in pH, temperature, atmospheric pressure, and concentrations of reactants and products
What is the free energy change (ΔG) of the hydrolysis of ATP to ADP?
hydrolysis
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
Positive
What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components?
In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.
When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations?
ΔS is positive
When one molecule is broken down into six component molecules, which of the following will always be true?
The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate
Which of the following best characterizes the role of ATP in cellular metabolism?
Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.
Which of the following correctly states the relationship between anabolic and catabolic pathways?
the free energy of the reactants and the free energy of the products
Which of the following determines the sign of ΔG for a reaction?
None of the listed responses is correct.
Which of the following environments or actions would NOT affect the rate of an enzyme reaction?
The active site can provide heat from the environment that raises the energy content of the substrate
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?
The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.
Which of the following is an example of the second law of thermodynamics as it applies to biological reactions?
The activation energy
Which of the following is changed by the presence of an enzyme in a reaction?
the activation energy
Which of the following is changed by the presence of an enzyme in a reaction?
Metabolism consists of all the energy transformation reactions in an organism
Which of the following is true of metabolism in its entirety in all organisms?
Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.
Which of the following is true regarding metabolic pathways?
Glucose + fructose → sucrose
Which of the following reactions would be endergonic?
The cycling between ATP and ADP + Pi provides an energy coupling between catabolic and anabolic pathways.
Which of the following statements about ATP (adenosine triphosphate) is correct?
they exist in active and inactive conformations; they are acted on by inhibitors; they are sensitive to environmental conditions.
Which of the following statements about allosteric proteins is/are true?
Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output
Which of the following statements about enzyme function is correct
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction
Which of the following statements about enzymes is true?
Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.
Which of the following statements about enzymes is true?
A reaction that is at equilibrium is not capable of doing any work.
Which of the following statements about equilibrium of chemical reactions is correct?
The final product of a metabolic pathway is usually the compound that regulates the pathway.
Which of the following statements about feedback regulation of a metabolic pathway is correct?
The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.
Which of the following statements about the active site of an enzyme is correct?
The entropy of the products is greater than the entropy of the reactants.
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct?
The energy from the hydrolysis of ATP may be directly coupled to endergonic processes by the transfer of the phosphate group to another molecule
Which of the following statements about the role of ATP in cell metabolism is true?
Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.
Which of the following statements correctly describes cofactors and coenzymes?
The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.
Which of the following statements is correct regarding ATP?
Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site
Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors?
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.
Which of the following statements is correct regarding kinetic and potential energy?
Cells require a continuous input of energy to maintain their high level of organization
Which of the following statements is representative of the second law of thermodynamics?
Energy can be freely transformed among different forms as long as the total energy is conserved.
Which of the following states the relevance of the first law of thermodynamics to biology?
The enzyme has an allosteric regulatory site
Which of the following would be unlikely to contribute to the substrate specificity of an enzyme?
heat, carbon dioxide, and water
Which of these are by-products of cellular respiration?
endergonic
Which of these reactions requires a net input of energy from its surroundings?
The action of competitive inhibitors may be reversible or irreversible.
Which of these statements about enzyme inhibitors is true?
γ-phosphate (the terminal phosphate)
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?
ΔG
Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous?
When substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape.
Which statement about the binding of enzymes and substrates is correct?
releasing free energy that can be coupled to other reactions
in general the hydrolysis of ATP drives cellular work by __________.
the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP
much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate group. these bonds are unstable because ___________.
the use of energy released from an exergonic reaction to drive an endergonic reaction
what is energy coupling?
The first and second choices are correct
which of the following statements correctly describe(s) the role or roles of heat in biological reactions?