Bio chapter 6 questions

Animals have enzymes that break apart starch molecules but not cellulose, despite the fact that both are made up of glucose subunits. Which enzyme characteristic best explains this? a. Enzymes are highly specific. b. Enzyme activity is regulated. c. Enzymes are not permanently changed by the reactions they promote. d. Enzymes usually speed up chemical reactions. e. All enzymes are proteins.

a

Sulfa antibiotics damage bacteria by affecting a certain bacterial enzyme. The sulfa antibiotic looks similar to a substrate normally required by the bacterial cells to live. The sulfa antibiotic occupies the active site of the required enzyme and blocks entry of its normal substrate. This prevents the bacteria from making nucleotides that are required for their reproduction and survival. Based on this information, the action of sulfa antibiotics is an example of a. competitive inhibition. b. denaturing of proteins. c. electron carriers. d. activation energy.

a

The addition of a competitive inhibitor slows down a particular reaction. What could be done to increase the rate of the reaction, even in the presence of the inhibitor? a. Add more substrate. b. Allow the reaction to reach equilibrium. c. Lower the temperature of the reaction. d. Add more inhibitor. e. Add a coenzyme

a

Enzymes are important because they a. increase the body temperature of organisms. b. allow reactions to occur at body temperature. c. bind irreversibly to substrates. d. can enable organisms to evade the laws of thermodynamics. e. are structural proteins that make up bodily tissues.

b

Place these steps of enzyme catalysis in the correct order: 1. The substrate and enzyme change shape. 2. The substrate enters the active site. 3. The enzyme reverts to its original configuration. 4. The product is expelled. a. 1, 3, 4, 2 b. 2, 1, 4, 3 c. 2, 3, 1, 4 d. 1, 2, 3, 4 e. 2, 1, 3, 4

b

ATP is an energy carrier. Where is the energy actually located? a. Inside the phosphate b. Attached to the nucleotide c. In the bonds between phosphate groups d. Between the sugar and the phosphate e. Attached to the phosphate group

c

The reactant in an enzyme-catalyzed reaction is the a. product. b. allosteric inhibitor. c. substrate. d. active site. e. activation energy.

c

Which of the following statements regarding enzymes is FALSE? a. An enzyme may be used many times for the same specific reaction. b. Enzymes are proteins that function as biological catalysts. c. Enzymes provide energy for the reactions they catalyze. d. Enzymes are highly specific for the molecules to which they attach. e. The activity of enzymes can be regulated by factors in their environment.

c

All of the following statements about catalysts are true EXCEPT a. catalysts are not permanently altered during reaction. b. catalysts can be used repeatedly. c. catalysts increase the reaction rate. d. catalysts increase activation energy requirements. e. biological catalysts are specific enzymes.

d

Competitive and noncompetitive enzyme inhibitors differ with respect to a. their pH. b. the temperature at which they work best. c. their energies of activation. d. the precise location on the enzyme to which they bind.

d

For many enzymes, the rate of product formation increases as the concentration of the substrate increases. Eventually the rate of the reaction reaches a maximum at which further increases in the concentration of the substrate have no effect. Why? a. The enzyme is no longer specific for the substrate. b. At high concentrations of substrate, the activation energy of the reaction decreases. c. At high concentrations of substrate, the reaction is endergonic. d. At high concentrations of substrate, all of the enzyme active sites are being occupied by substrate molecules. e. At high concentrations of substrate, the activation energy of the reaction increases.

d

Triclosan is a broad-spectrum antibacterial agent used in many household products. It is structurally similar to polychlorobiphenylol, a substrate that binds to the active site of the enzyme sulfotransferase. Based on these facts, you can conclude that triclosan most likely a. lowers the activation energy of chemical reactions. b. acts as a noncompetitive inhibitor. c. functions as an enzyme when sulfotransferase is absent. d. is a competitive inhibitor.

d

The end product of a biosynthetic pathway often acts to block the initial step in that pathway. This phenomenon is called a. substrate activation. b. allosteric activation. c. denaturation. d. irreversible inhibition. e. feedback inhibition.

e

Which of the following will bind to the active site of an enzyme? a. Competitive inhibitor only b. Allosteric inhibitor only c. Noncompetitive inhibitor only d. Substrate only e. Both substrate and competitive inhibitor

e

To say that an enzyme has been denatured means that a. its three-dimensional structure has changed and the enzyme can no longer function properly. b. the enzyme is working at an optimal temperature. c. an inhibitor has bound the enzyme at the active site. d. the enzyme is working at its maximal rate.

a

Which of the following lowers the activation energy of a biochemical reaction? a. Presence of a catalyst b. High concentration of products c. Low concentration of reactants d. Altering pH to 7 e. High temperature

a

Which of the following functions as a biological catalyst? a. Energy-carrier molecule b. Steroid c. Enzyme d. Substrate e. Amino acid

c

FADH2 is an example of a(n) a. active site. b. enzyme. c. enzyme-substrate complex. d. electron carrier molecule. e. protein

d