Metabolism Practice Test
The regulation of enzyme function is an important aspect of cell metabolism. Which of the following is least likely to be a mechanism for enzyme regulation?
removing cofactors
What name is given to the reactants in an enzymatically catalyzed reaction?
substrates
If an enzyme has been inhibited noncompetitively,
the inhibitor molecule may be chemically unrelated to the substrate.
Which of the following is true for all exergonic reactions?
the reaction proceeds with a net release of free energy; spontaneous.
The hydrolysis of ATP to ADP and inorganic phosphate (ATP + H2O-ADP- +Pi):
-has a ´G of about -7 kcal/mol under standard conditions. -involves hydrolysis of a terminal phosphate bond of ATP. -can occur spontaneously under appropriate conditions.
Which of the following reactions is most likely to be coupled to the reaction ATP + H2O-ADP +Pi ( 'G = -7.3 kcal/mol)?
+Pi-EP ('G = +5 kcal/mol)
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
Which of the following statements is true regarding enzyme cooperativity?
A substrate molecule bound to an active site affects the active site of several subunits
As temperature decreases, the rate of enzyme-catalyzed reaction also decreases. Which of the following explain(s) why this occurs?
A&B; fewer substrates have sufficient energy to get over the activation energy barrier, motion in the active site of the enzymes is slowed, thus slowing the catalysis of the enzyme
Which of the following statements regarding ATP is (are) correct?
ATP serves as a main energy shuttle inside cells, ATP drives endergonic reactions in the cell by the enzymatic transfer of the phosphate group to specific reactants, and the regeneration of ATP from ADP and phosphate is an endergonic reaction.
Which of the following describe(s) some aspect of metabolism?
Breakdown of macromolecules
Which of the following metabolic processes can occur without an input of energy?
C6H12O6 + 6O2 is converted to 6CO2 + 6H2O
Which of these statements regarding enzymes is true?
Enzymes are proteins that function as catalysts, enzymes display specificity for certain molecules with which they interact, the activity of enzymes can be regulated by other molecules, and an enzyme may be used many times over for a specific reaction
Which of the following is true of enzymes?
Enzymes may require a nonprotein cofactor or ion for catalysis to take place. Enzyme function is reduced if the three-dimensional structure or conformation of an enzyme is altered. Enzyme function is influenced by physical and chemical environmental factors such as pH and temperature. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.
A series of enzymes catalyze the reaction X _Y _Z _ ± | n 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. What is substance X?
a substrate
Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reactions:
activation energy
How can one increase the rate of a chemical reaction?
add a catalyst
If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is to
add more of the enzyme
A series of enzymes catalyze the reaction X _Y _Z _ ± | n 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. Substance A functions as
an allosteric inhibitor
How does a non-competitive inhibitor decrease the rate of an enzyme reaction?
by changing the structure of the enzyme
Which term precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
When 10,000 molecules of ATP are hydrolyzed to ADP and Pi in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanations for this observation?
cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
cellular respiration
Many different things can alter enzyme activity. Which of the following underlie all types of enzyme regulation?
changes in the activation energy of the reaction, and changes in 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(n)
cofactor necessary for enzyme activity
Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
ATP generally energizes a cellular process by
coupling free energy released by ATP hydrolysis to free energy needed by other reactions
A chemical reaction that has a positive 'G is correctly described as
endergonic; non-spontaneous; energy required.
Which of the following statements regarding enzymes is true?
enzymes increase the rate of a reaction
Which of the following is not true of enzymes?
enzymes provide activation energy for the reaction they catalyze
The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as
feedback inhibition
The active site of an enzyme is the region that
is involved in the catalytic reaction of the enzyme
An enzyme catalyzes a reaction by
lowering energy of activation of a reaction
Which of the following is (are) true for anabolic pathways?
they consume energy to build up polymers from monomers
Which of the following statements correctly describes catabolic pathways?
they release energy as they degrade polymers to monomers
