Biology Chapter 8 Metabolism

* A series of enzymes catalyze the reaction X to Y to Z to A. 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?

* Selected Answer: C. a substrate

noncompetitive inhibitor

A reversible inhibitor that binds somewhere other than the active site

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a delta G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the delta G for the new reaction?

B. -20 kcal/mol

Which of the following statements regarding enzymes is true?

B. Enzymes increase the rate of a reaction.

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

B. activation energy.

* The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is known as * Selected Answer:

B. feedback inhibition.

The active site of an enzyme is the region that

B. is involved in the catalytic reaction of the enzyme.

An enzyme catalyzes a reaction by

B. lowering the energy of activation of a reaction.

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?

C. competitive inhibition

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 explanation for this observation?

E. Cells convert some of the energy of ATP hydrolysis into other forms of energy besides heat.

coenzyme

If the cofactor is an organic molecule.

competitive inhibitors

Reduce the productivity of enzymes by blocking substrates from entering active sites.

* If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is to *

Selected Answer: A. add more of the enzyme.

* A series of enzymes catalyze the reaction X to Y to Z to A. 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 *

Selected Answer: B. an allosteric inhibitor.

* How does a non-competitive inhibitor decrease the rate of an enzyme reaction? *

Selected Answer: B. by changing the structure of the enzyme *

* In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP? *

Selected Answer: B. cellular respiration *

* 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) *

Selected Answer: D. cofactor necessary for enzyme activity.

* 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? *

Selected Answer: D. removing cofactors

* If an enzyme has been inhibited noncompetitively, *

Selected Answer: E. the inhibitor molecule may be chemically unrelated to the substrate.

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 describe(s) catabolic pathways?

They release energy as they degrade polymers to monomers.

How can one increase the rate of a chemical reaction?

add a catalyst (such as an enzyme)

-may either inhibit or stimulate an enzyme's activity -binding of a modulator at a site other than the active site

allosteric regulation

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

catabolism

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.

free energy

energy that is available to do work

the end product of a metabolic pathway shuts down the pathway concentration of product at the end of a pathway blocks the action of a key enzyme

feedback inhibition

negative delta G

free energy is decreased, spontaneous, down hill, catabolic, exergonic

ATP generation

generated by phosphorylation of ADP

positive delta G

must add energy for process to occur anabolic processes endergonic Non spontaneous

most cells cannot harness heat to perform work because

temperature is usually uniform throughout a cell.

factors that influence rate of catalyzed reaction

temperature, influences on protein shape (pH, temp., ion conc.), enzyme/substrate concentration, binding strength

cofactors

the presence of molecules like coenzymes or vitamins allow enzymes to be active

some bacteria are metabolically active in hot springs because

their enzymes have high optimal temperatures

change in free energy

🔼G=🔼H-T🔼S tells us whether or not a reaction occurs spontaneously; ΔG = Gf - Gi