BSC 114 Chapter 8

In cells, what is usually the immediate source of energy for an endergonic reaction? 1--ATP 2--as spontaneous reactions, endergonic reactions do not need an addition of energy 3--glucose 4--ADP 5--sugar

1

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? 1--catabolism 2--metabolism 3--anabolism 4--dehydration 5--catalysis

1

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct? 1--The binding of the substrate depends on the shape of the active site. 2--The binding of the substrate changes the shape of the enzyme's active site. 3--The active site creates a microenvironment ideal for the reaction. 4--A competitive inhibitor can outcompete the substrate for the active site. 5--Some enzymes change their structure when activators bind to the enzyme.

2

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's... 1-- endothermic level. 2--activation energy. 3--entropy. 4--heat content. 5--free-energy content.

2

Sucrose is a disaccharide, composed of the monosaccharides glucose and fructose. The hydrolysis of sucrose by the enzyme sucrase results in... 1--bringing glucose and fructose together to form sucrose. 2--breaking the bond between glucose and fructose and forming new bonds from the atoms of water. 3--utilization of water as a covalent bond is formed between glucose and fructose to form sucrase. 4--the release of water from sucrose as the bond between glucose and fructose is broken. 5--production of water from the sugar as bonds are broken between the glucose monomers.

2

The reaction A --> B + C + heat is released in a(n) _____ reaction. 1--endergonic 2--exergonic 3--anabolic 4--exchange 5--dehydration synthesis

2

A series of enzymes catalyze the reaction X→Y→Z→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 1--a coenzyme. 2--the substrate. 3--an allosteric inhibitor. 4--a competitive inhibitor. 5--an intermediate.

3

How does an enzyme increase the rate of the chemical reaction it catalyzes? 1--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. 2--An enzyme reduces the free-energy change (ΔG) of the reaction it catalyzes. 3--An enzyme reduces the free energy of activation (EA) of the reaction it catalyzes.

3

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? 1--such mutations could occur anywhere with equal probability 2--at a cofactor binding site 3--in or near the active site 4--in regions of the protein that determine packaging into the virus capsid 5--at an allosteric site

3

The following question is based on the reaction A+B→C+D shown in the figure. Which best describes the reaction? 1--The difference between "b" and "c" is the activation energy added by the presence of the enzyme. 2--The amount of free energy released as a result of the noncatalyzed reaction is indicated by "c." 3--The amount of free energy released as a result of the catalyzed reaction is indicated by "d." 4--The amount of free energy present in the products is indicated by "e." 5--The amount of free energy initially present in the reactants is indicated by "a."

3

The reaction ADP + P --> ATP is a(n) _____ reaction. 1--exergonic 2--spontaneous 3--endergonic 4--chemical 5--hydrolysis

3

Which of the following is true for all exergonic reactions? 1--Some reactants will be converted to products. 2--The products have more total energy than the reactants. 3--The reaction proceeds with a net release of free energy. 4--A net input of energy from the surroundings is required for the reactions to proceed. 5--The reactions are nonspontaneous.

3

Which of the following is true of enzymes? 1--Enzyme function is independent of physical and chemical environmental factors such as pH and temperature. 2--Enzymes may require a nonprotein cofactor or ion for catalysis to take speed up more appreciably than if the enzymes act alone. 3--Enzymes increase the rate of chemical reaction by lowering activation energy barriers. 4--Enzyme function is increased if the three-dimensional structure or conformation of an enzyme is altered.

3

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)... 1--allosteric activator of the enzyme. 2--noncompetitive inhibitor of the enzyme. 3--cofactor necessary for enzyme activity. 4--competitive inhibitor of the enzyme. 5--coenzyme derived from a vitamin.

3

A(n) _____ reaction occurs spontaneously. 1--endergonic 2--chemical 3--kinetic 4--exergonic 5--anabolic

4

The active site of an enzyme is the region that... 1--binds the products of the catalytic reaction. 2--is inhibited by the presence of a coenzyme or a cofactor. 3--binds allosteric regulators of the enzyme. 4--is involved in the catalytic reaction of the enzyme.

4

What is energy coupling? 1--the use of an enzyme to reduce EA 2--a description of the energetic relationship between the reactants and products in an exergonic reaction 3--a barrier to the initiation of a reaction 4--the use of energy released from an exergonic reaction to drive an endergonic reaction 5--the hydrolysis of ATP to ADP + P

4

A chemical reaction that has a positive ΔG is correctly described as... 1--enthalpic 2--spontaneous 3--exothermic 4--endothermic 5--endergonic

5

The energy for an endergonic reaction comes from a(n) _____ reaction. 1--glucose + glucose --> maltose 2--synthesis 3--anabolic 4--ADP + P --> ATP 5--exergonic

5

What is the fate of the phosphate group that is removed when ATP is converted to ADP? 1--It is acquired by a reactant in a spontaneous reaction. 2--It is acquired by a reactant in an exergonic reaction. 3--It is broken down into one phosphorus and four oxygen atoms. 4--It is used to convert an ATP into an AQP. 5--It is acquired by a reactant in an endergonic reaction.

5