Mastering Biology HW Chapter 8
The reaction ADP + P --> ATP is a(n) _____ reaction.
endergonic
This graph illustrates a(n) _____ reaction.
endergonic
Which of these reactions requires a net input of energy from its surroundings?
endergonic
What is the correct label for "A"?
energy of activation
A(n) _____ reaction occurs spontaneously.
exergonic
The energy for an endergonic reaction comes from a(n) _____ reaction.
exergonic
The following reactionA --> B + C + heat is a(n) _____ reaction.
exergonic
Select the INCORRECT association.
exergonic ... uphill
Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _______ is to _______.
exergonic; endergonic
In this reaction _____.
heat has been released to the environment
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
hydrolysis
Which of the following would increase the rate of the reverse reaction?
increasing the concentration of ammonia
An enzyme _____.
is an organic catalyst
As a result of its involvement in a reaction, an enzyme _____.
is unchanged
When is the rate of reaction the fastest during this simulation run?
minutes 0-4
What is the optimal pH for the rate of reaction for the lactase enzyme in this simulation?
pH 7
In general, enzymes are what kinds of molecules?
proteins
Enzymes work by _____.
reducing EA
Look at the graph of reaction rate versus substrate concentration for an enzyme. In which region does the reaction rate remain constant?
region C
Refer again to the graph. In which region is the enzyme saturated with substrate?
region C
What name is given to the reactants in an enzymatically catalyzed reaction?
substrate
Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes?
the active site can provide heat from the environment that raises the energy content of the substrate
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 compound is a competitive inhibitor
In this reaction _____.
the products have less potential energy than the reactants
What is energy coupling?
the use of energy released from an exergonic reaction to drive an endergonic reaction
Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?
γ-phosphate (the terminal phosphate)
If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
Nothing; the reaction will stay at equilibrium.
Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown?
P4 binds E1 and deactivates it.
The process of cellular respiration, which converts simple sugars such as glucose into CO2 and water, is an example of __________.
a catabolic pathway
What is the optimal temperature for the fastest rate of reaction for the lactase enzyme?
37
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
It is acquired by a reactant in an endergonic reaction.
Which of the following statements about equilibrium of chemical reactions is correct?
A reaction that is at equilibrium is not capable of doing any work.
In cells, what is usually the immediate source of energy for an endergonic reaction?
ATP
You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again?
Add more substrate; it will outcompete the inhibitor and increase the reaction rate.
At a certain concentration of substrate, there will be a "point of saturation" when the rate of the reaction will plateau. In this experiment, increasing the concentration of lactose beyond 500 mg/dL does not increase the rate of reaction further. What is the best explanation for this phenomenon?
At 500 mg/dL of lactose, the lactase enzymes are fully saturated with substrate.
What will happen to the rates of the forward and reverse reactions when a catalyst is added?
Both forward and reverse rates increase.
A chemical reaction occurs between the amino acids alanine (Ala) and glycine (Gly), forming the compound alanylglycine. The simple conversion reaction of alanine and glycine into this compound is endergonic, with a ΔΔG of 6.9 kcal/mol. Therefore, it requires ATP hydrolysis to drive the nonspontaneous reaction. Calculate the free energy change for the whole process, applying what you know about ATP hydrolysis.
G = -0.4 kcal/mol
Consider a situation in which the enzyme is operating at optimum temperature and pHpH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?
Increase the enzyme concentration
How does the phosphorylation of glutamic acid (Glu) provide energy for the rest of the reaction to occur?
The addition of a phosphate to Glu forms a phosphorylated intermediate with more free energy than Glu. The ammonia can thus displace the phosphate in an exergonic reaction.
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 entropy of the products is greater than the entropy of the reactants.
You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme?
The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.
Which of the following statements about feedback inhibition of a metabolic pathway is correct?
The final product of a metabolic pathway is usually the compound that regulates the pathway.
What do you notice about the reaction rate at the three different lactose concentrations?
The rate of reaction at 250 mg/dL compared to 500 mg/dL is slower The rate of reaction at 750 mg/dL compared to 500 mg/dL is the same
The Haber process is typically carried out at a temperature of approximately 500∘C∘C. What would happen to the rate of the forward reaction if the temperature were lowered to 100∘C∘C?
The reaction rate would decrease.
What would happen to the rate of the forward reaction if the concentration of nitrogen were decreased?
The reaction rate would decrease.
