Bio 114 Chapter 8 HW Questions

In Cells, what is usually the immediate source of energy for an endergonic reaction? A. ATP B. ADP C. as spontaneous reactions, endergonic reactions do not need an addition of energy D. glucose E. sugar

A. ATP (The hydrolysis of ATP provides the energy needed for an endergonic reaction)

How does an enzyme increase the rate of the chemical reaction it catalyzes? A. An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes. B. An enzyme reduces the free-energy change ( ΔG ) of the reaction it catalyzes. C. An enzyme's active site binds only the reactants, and not the products of a reaction, pushing the equilibrium for the reaction far to the right.

A. An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes. (An enzyme catalyzes a reaction by lowering Ea, enabling the reactant molecules to absorb enough energy to reach the transition state even at moderate temperature.)

Which of the following is true for all exergonic reactions? A. The reaction proceeds with a net release of free energy. B. The products have more total energy than the reactants C. A net input of energy from the surroundings is required for the reactions to proceed. D. Some reactants will be converted to products E. The reactions are nonspontaneous

A. The reaction proceeds with a net release of free energy.

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) A. noncompetitive inhibitor of the enzyme B. cofactor necessary for enzyme activity C. coenzyme derived from a vitamin. D. competitive inhibitor of the enzyme. E. allosteric activator of the enzyme.

B. Cofactor necessary for enzyme activity

Which of the following is true of enzymes? A. Enzymes may require a nonprotein cofactor or ion for catalysis to take speed up more appreciably than if the enzymes act alone B. Enzymes increase the rate of chemical reaction by lowering activation energy barriers. C. Enzyme function is increased if the three-dimensional structure or conformation of an enzyme is altered. D. Enzyme function is independent of physical and chemical environmental factors such as pH and temperature.

B. Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

The reaction A --> B + C + heat is released in a(n) _____ reaction. A. Exchange B. Exergonic C. Dehydration Synthesis D. Endergonic E. anabolic

B. Exergonic (Energy has been released)

The energy for an endergonic reaction comes from a(n) _____ reaction A. Synthesis B. Exergonic C. ADP + P --> ATP D. Anabolic E. glucose + glucose --> maltose

B. Exergonic (Energy released by an exergonic reaction can be used to drive an endergonic reaction)

The active site of an enzyme is the region that A. Binds the products of the catalytic reaction B. Is involved in the catalytic reaction of the enzyme C. Binds allosteric regulators of the enzymes D. is inhibited by the presence of a coenzyme or a cofactor

B. Is involved in the catalytic reaction of the enzyme

What is the fate of the phosphate group that is removed when ATP is converted to ADP? A. It is used to convert an ATP into an AQP B. It is acquired by a reactant in an endergonic reaction. C. It is acquired by a reactant in a spontaneous reaction D. It is broken down into one phosphorus and four oxygen atoms. E. It is acquired by a reactant in an exergonic reaction

B. It is acquired by a reactant in an endergonic reaction. (By acquiring the phosphate group the reactant requires energy)

Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in A. production of water from the sugar as bonds are broken between the glucose monomers. B. breaking the bond between glucose and fructose and forming new bonds from the atoms of water. C. bringing glucose and fructose together to form sucrose. D. the release of water from sucrose as the bond between glucose and fructose is broken. E. utilization of water as a covalent bond is formed between glucose and fructose to form sucrase

B. breaking the bond between glucose and fructose and forming new bonds from the atoms of water.

The reaction ADP + P --> ATP is a(n) _____ reaction. A. Chemical B. Kinetic C. Endergonic D. Exergonic E. Spontaneous

C. Endergonic (Energy has been acquired from its surroundings)

A(n) _____ reaction occurs spontaneously. A. chemical B. kinetic C. Exergonic D. Endergonic E. Anabolic

C. Exergonic (In exergonic reactions the products have less potential energy than the reactants)

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? A. The active site creates a microenvironment ideal for the reaction. B. Some enzymes change their structure when activators bind to the enzyme C. The binding of the substrate changes the shape of the enzyme's active site. D. A competitive inhibitor can outcompete the substrate for the active site. E. The binding of the substrate depends on the shape of the active site.

C. The binding of the substrate changes the shape of the enzyme's active site.

Some of the drugs used to treat HIV patients are competitive inhibitors of the HIV reverse transcriptase enzyme. Unfortunately, the high mutation rate of HIV means that the virus rapidly acquires mutations with amino acid changes that make them resistant to these competitive inhibitors. Where in the reverse transcriptase enzyme would such amino acid changes most likely occur in drug-resistant viruses? A. such mutations could occur anywhere with equal probability B. in regions of the protein that determine packaging into the virus capsid C. at an allosteric site D. in or near the active site E. at an cofactor binding site

D. In or near the active site

What is energy coupling? A. the use of an enzyme to reduce EA B. the hydrolysis of ATP to ADP + P C. a barrier to the initiation of a reaction D. the use of energy released from an exergonic reaction to drive an endergonic reaction E. a description of the energetic relationship between the reactants and products in an exergonic reaction

D. The use of energy released from an exergonic reaction to drive an endergonic reaction.

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's A. Entropy B. Heat Content C. Endothermic level D. Free-energy Content E. Activation Energy

E. Activation Energy

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A. Anabolism B. Catalysis C. Metabolism D. Dehydration E. Catabolism

E. Catabolism

A chemical reactions that has a positive (Delta)G is correctly described as A. endothermic B. spontaneous C. Exothermic D. Enthalpic E. Endergonic

E. Endergonic