Microbiology: Chapter 10

In a branched pathway with many end products, an abundance of one of the end products will usually inhibit A. the first step in the set of pathways. B. the first committed step in the branch of the pathway leading to the production of that particular product. C. the last step before the branch leading to the production of that particular end product. D. the last step in the production of that particular product.

B. the first committed step in the branch of the pathway leading to the production of that particular product.

A reaction in which forward rate is equal to the reverse rate is said to be at ________________

Equilibrium

Enzymes increase the rate of a reaction by increasing molecular motion, thereby providing kinetic energy to drive the reaction. True/False

False

One important ribozyme located in mitochondria is responsible for catalyzing peptide bond formation during protein synthesis. True/False

False

The Michaelis constant (Km) of an enzyme is the substrate concentration that produces maximum velocity. True/False

False

The electron transport chain is based on the principle that redox couples with more positive reduction potentials will donate electrons to couples with more negative potentials.

False

The most commonly used practical form of energy used in cells is adenosine diphosphate. True/False

False

The numerical value of the free energy change indicates how fast a reaction will reach equilibrium. True/False

False

When the amount of enzyme present is held constant, the rate of a reaction will continue to increase as long as the substrate concentration increases. True/False

False

____________ is the total of all chemical reactions occurring in the cell

Metabolism

The __________ ___________ is the substrate concentration needed fro an enzyme to achieve half maximal velocity

Michaelis constant (Km)

______________ is the science that analyzes energy changes in a collection of matter

Thermodynamics

Each enzyme normally has specific pH and temperature optima at which they function best. True/False

True

Energy can be redistributed within a collection of matter (called a system) or can be redistributed between the system and its surroundings. True/False

True

Enzyme activity can be greatly affected by the pH and the temperature of the environment in which the enzyme must function. True/False

True

Enzymes increase the rate of a reaction but do not alter equilibrium constants. True/False

True

Isoenzymes are different enzymes that catalyze the same reaction but can be regulated independently of one another. True/False

True

One of the components used during photosynthetic electron transport is ferredoxin, a nonheme iron protein.

True

Some endergonic reactions can be made to proceed forward if they are coupled to hydrolysis of one or more of the phosphates of ATP. True/False

True

The equilibrium constant for a redox reaction is called the standard reduction potential. True/False

True

A molecule that binds noncovalently to an enzyme at the actie site and thereby prevents a substrate from binding and reacting is a(n) _______________ inhibitor

competitive

Disruption of an enzymes structure with loss of activity caused by extremes of pH, temperature, or other factors is called ___________

denaturation

Cells must efficiently transfer energy from their energy-trapping systems to the systems actually carrying out work and also various metabolic processes to replace the energy used in doing work. This is called the _________

energy cycle

A molecule that binds to an enzyme at a location other than the active site and thereby alters the enzymes shape, making it inactive or less active is a(n) ___________ inhibitor

noncompetitive

The molecules formed by an enzyme-catalyzed reaction are called __________

products

RNA molecules that have catalytic activity that are known as _____________

ribozymes

The reacting molecules in an enzyme-catalyzed reaction are called _________

substrates

In thermodynamic studies, energy changes are analyzed in a collection of matter called a ____________. All other matter in the universe is called the ____________

system; surroundings

A complex formed during a reaction that resembles both the substrate and products is called the _________ state complex

transition

For the reaction A + B C + D, the equilibrium constant (Keq) is defined as A. [A][B]/[C][D]. B. [C][D]/[A][B]. C. [A][D]/[B][C]. D. [B][C]/[A][D].

B.

__________ is the total energy change that accompanies a chemical reaction. A. Entropy B. Enthalpy C. Free energy D. Synergy

B. Enthalpy

Cells carry out three major types of work; which of the following involves nutrient uptake and waste elimination? A. Chemical work. B. Transport work. C. Mechanical work. D. None of these.

B. Transport work

The energy required to bring the substrates of a reaction together in the correct way to reach the transition state is called A. free energy. B. activation energy. C. enthalpy. D. entropy.

B. activation energy

The substrate of an enzyme binds at the A. affinity site. B. active site. C. determinative site. D. reaction site.

B. active site

The amount of heat energy needed to raise 1 gram of water from 14.5C to 15.5C is called a(n) A. joule. B. calorie. C. erg. D. thermal unit.

B. calorie

A(n) _______________ increases the rate of a reaction without being permanently altered by the reaction. A. catalyzer B. catalyst C. enzyme D. rate increaser

B. catalyst

A nonprotein component of an enzyme that is loosely attached to the protein component is referred to as a(n) A. apoenzyme. B. coenzyme. C. holoenzyme. D. prosthetic group.

B. coenzyme

When the end product of a pathway inhibits catalysis of the first step of that pathway, this phenomenon is called A. reversible covalent modification. B. feedback inhibition. C. metabolic channeling. D. non-competitive inhibition.

B. feedback inhibition.

In metabolic channeling, the regulation of metabolic pathways is controlled by the __________ of metabolites and enzymes involved in the pathway. A. amount B. location C. activity D. all of the choices

B. location

The standard reduction potential of a redox reaction is a measure of the tendency of the __________ to __________ electrons. A. reductant; gain B. reductant; lose C. oxidant; gain D. oxidant; lose

B. reductant; lose

_______________ reactions build new organic molecules from smaller inorganic and organic compounds

Anabolic

The __________ is the electron acceptor in a redox reaction. A. reductant B. oxidant C. enzyme D. product

b. oxidant

Cells carry out three major types of work; which of the following involves the synthesis of macromolecules as well as the breakdown of substances for their energy? A. Chemical work B. Transport work C. Mechanical work D. None of these

A. Chemical work

__________ is a measure of the randomness or disorder of a system. A. Entropy B. Enthalpy C. Free energy D. Synergy

A. Entropy

A reaction that releases energy is __________. A. exergonic B. endergonic C. impossible D. none of the choices

A. exergonic

The __________ law of thermodynamics states that energy can be neither created nor destroyed. A. first B. second C. third D. fourth

A. first

The __________ is the electron donor in a redox reaction. A. reductant B. oxidant C. enzyme D. product

A. reductant

In order for the cell to be able to input energy into necessary endergonic reactions, energy-generating processes such as photosynthesis, fermentation, and respiration are used to produce ________

ATP

Cells carry out three major types of work; which of the following involves energy for cell motility and the movement of structures within cells? A. Chemical work. B. Transport work. C. Mechanical work. D. None of these.

C. Mechanical work

Enzymes function as catalysts by A. bringing the substrates together at the active site, in effect concentrating them. B. bringing the substrates together at the active site correctly oriented for the reaction. C. bringing the substrates together at the active site, in effect concentrating them and bringing the substrates together at the active site correctly oriented for the reaction. D. none of the choices

C. bringing the substrates together at the active site, in effect concentrating them and bringing the substrates together at the active site correctly oriented for the reaction.

Enzymes catalyze a reaction by A. decreasing the amount of energy released by the reaction. B. increasing the amount of energy released by the reaction. C. decreasing the activation energy of the reaction. D. increasing the activation energy of the reaction. D. increasing the activation energy of the reaction.

C. decreasing the activation energy of the reaction.

The most specific term usually used to describe a substance in a biological system that increases the rate of a reaction without being permanently changed by the reaction is a(n) A. catalyzer. B. catalyst. C. enzyme. D. rate increaser.

C. enzyme

The change in __________ is the amount of energy in a system that is available to do work. A. entropy B. enthalpy C. free energy D. synergy

C. free energy

A complete enzyme that consists of a protein component and a nonprotein component is called a(n) A. apoenzyme. B. heteroenzyme. C. holoenzyme. D. multienzyme

C. holoenzyme

In allosteric regulation, effector molecules usually bind A. reversibly and covalently. B. irreversibly and covalently. C. reversibly and noncovalently. D. irreversibly and noncovalently.

C. reversibly and noncovalently.

Metabolic channeling involves the localization of __________ in different parts of a cell in order to influence the activity of metabolic pathways. A. activators B. repressors C. substrates and enzymes D. inhibitors

C. substrates and enzymes

___________ reactions capture energy from the organisms energy source

Catabolic

The __________ law of thermodynamics states that physical and chemical processes occur in such a way that randomness (disorder) increases to a maximum. A. first B. second C. third D. fourth

b. second

Which of the following is a reason for metabolic regulation? A. Maintain cell components at appropriate levels. B. Conserve materials. C. Ensure efficient use energy stores. D. All of the choices.

D. All of the choices

Enzyme activity can be controlled by A. allosteric regulation. B. covalent modification. C. feedback (end product) inhibition. D. all of the choices

D. all of the choices

Which of the following is not true about enzymes? A. Enzymes are catalysts that speed up reactions. B. Enzymes are proteins that can be denatured by changes in pH or temperature. C. Enzymes are highly specific for the substrates they react with and catalyze only one or a limited set of possible reactions with those substrates. D. all of the choices

D. all of the choices

Which of the following is used as an electron carrier by living organisms? A. NAD+ B. NADP+ C. ubiquinone D. all of the choices

D. all of these choices

Electron transport molecules that only transfer electrons include A. ubiquinone. B. NADP. C. FAD. D. ferredoxin.

D. ferredoxin

The nonprotein component of an enzyme that is firmly attached to the protein is called a(n) A. apoenzyme. B. coenzyme. C. holoenzyme. D. prosthetic group.

D. prosthetic group

Enzymes are usually named based on A. the substrates they act on. B. their molecular structure. C. the type of reaction they catalyze. D. all of the choices. E. the substrates they act on and the type of reaction they catalyze.

E. the substrates they act on and the type of reaction they catalyze.

If an enzyme consists of a protein component and a non-protein component, the protein component is referred as the A. apoenzyme. B. coenzyme. C. holoenzyme. D. prosthetic group.

apoenzyme

An chemical reaction that requires an input of energy in order to proceed is __________. A. exergonic B. endergonic C. impossible D. one of the choices

b. endergonic

If all available enzyme molecules are binding substrate and converting it to produce as rapidly as possible, the reaction is said to be proceeding at __________ velocity. A. terminal B. maximal C. optimal D. infinite

b. maximal