Chapter 10

T/F 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

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

FALSE

T/F Enzymes decrease the overall free energy change in a chemical reaction

False

T/F In an ATP molecule, the phosphates are bonded to the adenine ring.

False

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

False

T/F The most commonly used practical form of energy used in cells is adenosine diphosphate.

False

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

False

T/F 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.

False

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

False

The regulatory site in an allosteric enzyme is found within the catalytic site.

False

When the end product of a pathway inhibits catalysis of the first step of that pathway, this phenomenon is called

Feedback Inhibition

The __________ law of thermodynamics states that energy can be neither created nor destroyed.

First

The change in __________ is the amount of energy in a system that is available to do work.

Free Energy

What nucleoside trisphosphate, other than ATP, provides some of the energy for protein synthesis?

GTP

Which of the following is a reason for metabolic regulation?

Maintain cell components at appropriate levels, Conserve materials and Ensure efficient use of energy stores

Cells carry out three major types of work; which of the following involves energy for cell motility and the movement of structures within cells?

Mechanical work

_________ is the total of all chemical reactions occurring in the cell.

Metabolism

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

Michaelis constant (Km)

Which of the following is used as an electron carrier by living organisms?

NAD+ NADP+ Ubiquinone D. All of the choices are correct.

In a redox reaction involving NAD/NADH and pyruvate, _____________ will be the electron donor and ____________ will be the electron acceptor.

NADH; pyruvate

Which of the following reactions is catalyzed by a ribozyme?

Peptide bond formation during protein synthesis

Based on phosphate transfer potential, which is more likely to happen?

Phosphoenolpyruvate will transfer phosphate to ADP

Where is the electron transport chain located in bacterial cells?

Plasma membrane

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

TRue

T/F Enzymes increase the rate of a reaction but do not alter equilibrium constants.

TRue

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

Thermodynamics

Cells carry out three major types of work; which of the following involves nutrient uptake and waste elimination?

Transport Work

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

True

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

True

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

True

T/F The equilibrium constant for a redox reaction is called the standard reduction potential.

True

T/F Covalent modification of enzymes most commonly uses phosphoryl, methyl, and adenyl groups.

True

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

True

T/F 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

What nucleoside trisphosphate provides energy for lipid synthesis?

UTP

56. A(n) _______________ increases the rate of a reaction without being permanently altered by the reaction.

catalyst

52. A nonprotein component of an enzyme that is loosely attached to the protein component is referred to as a(n)

coenzyme

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

competitive

Disruption of an enzyme's structure with loss of activity caused by extremes of pH, temperature, or other factors is called _________.

denaturation

An chemical reaction that requires an input of energy in order to proceed is __________.

endergonic

49. 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)

enzyme.

Catalytic proteins are known as ___________ whereas catalytic RNA molecules are known as ____________.

enzymes; ribozymes

A reaction in which the forward rate is equal to the reverse rate is said to be at __________. equilibrium

equilibrium

A reaction that releases energy is __________.

exergonic

When the end product of a pathway inhibits catalysis of the first step of that pathway, this phenomenon is called

feedback inhibition

Electron transport molecules that only transfer electrons include

ferredoxin.

59. The energy required to bring the substrates of a reaction together in the correct way to reach the transition state is called

free energy. B. activation energy. C. enthalpy. D. entropy.

The binding of a positive allosteric regulator molecule will

increase the ability of the substrate to bind to the catalytic site.

A positive allosteric effector will ____________ the activity of an enzyme while a negative effector will _______________ the activity.

increase; decrease

As the difference in reduction potential between a redox pair increases, the amount of free energy made available _______________.

increases

In metabolic channeling, the regulation of metabolic pathways is controlled by the __________ of metabolites and enzymes involved in the pathway.

location

55. If all available enzyme molecules are binding substrate and converting it to product as rapidly as possible, the reaction is said to be proceeding at __________ velocity.

maximal

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

noncompetitive

The __________ is the electron acceptor in a redox reaction.

oxidant

In bacterial and archaeal cells, the electron transport chain is located in the _________ whereas in eukaryotic cells, the electron transport chain is located in the ____________.

plasma membrane; inner mitochondrial membrane

Feedback inhibition, covalent modification, and allosteric regulation are all examples of ________________.

posttranslational regulation

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

products

53. The nonprotein component of an enzyme that is firmly attached to the protein is called a(n)

prosthetic group

The __________ is the electron donor in a redox reaction

reductant

The standard reduction potential of a redox reaction is a measure of the tendency of the __________ to __________ electrons.

reductant; lose

In allosteric regulation, effector molecules usually bind

reversibly and noncovalently.

RNA molecules that have catalytic activity are known as ____________.

ribozymes

Until the discovery of ______________, enzymes were the only recognized biological molecules that were catalytic.

ribozymes

The __________ law of thermodynamics states that physical and chemical processes occur in such a way that randomness (disorder) increases to a maximum.

second

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

substrates

Metabolic channeling involves the localization of __________ in different parts of a cell in order to influence the activity of metabolic pathways.

substrates and enzymes

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

In a branched pathway with many end products, an abundance of one of the end products will usually inhibit

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

Consider a biochemical pathway with five steps that lead to the production of product Q. If there is an abundance of product Q, the most efficient way to slow down the entire pathway would be to regulate _____________________.

the first enzyme in the pathway

48. Enzymes are usually named based on

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

A complex formed during a reaction that resembles both the substrates and the products is called the __________ state complex.

transition

Consider a biochemical pathway that branches to form two different products. If the end product of one of the branches is present in a large amount, at what point would the pathway be regulated to ensure adequate production of the end product of the alternative pathway while slowing or stopping production of the product already present in excess?

At the point where the two pathways branch

54. If an enzyme consists of a protein component and a non-protein component, the protein component is referred as the

Apoenzyme

________ reactions build new organic molecules from smaller inorganic and organic compounds.

Anabolic

Which strategy can be used for regulation of metabolism?

A. Feedback inhibition B. Allosteric regulation C. Regulation of enzyme synthesis D. Covalent modification of enzymes E. All of the choices are correct.

Enzyme activity can be controlled by

A. allosteric regulation. B. covalent modification. C. feedback (end product) inhibition. D. All of the choices are correct.

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

The energy made available during cell respiration and fermentation is used to make ______________, which is then available to provide energy for cellular work.

ATP

ATP has a phosphate transfer potential of 30.5, whereas glucose-6-phosphate has a phosphate transfer potential of 13.8. Based on these differences, which of the following will happen?

ATP will transfer phosphate to glucose-6-phosphate.

Enzymes catalyze a reaction by

C. decreasing the activation energy of the reaction.

51. A complete enzyme that consists of a protein component and a nonprotein component is called a(n)

C. holoenzyme

The amount of heat energy needed to raise 1 gram of water from 14.5C to 15.5C is called a(n)

Calorie

__________ reactions capture energy from the organisms' energy source.

Catabolic

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?

Chemical Work

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

Energy cycle

__________ is the total energy change that accompanies a chemical reaction.

Enthalpy

__________ is a measure of the randomness or disorder of a system.

Entropy

Which of the following is/are true about enzymes?

Enzymes are catalysts that speed up reactions. Enzymes are proteins that can be denatured by changes in pH or temperature. Enzymes are highly specific for the substrates they react with and catalyze only one or a limited set of possible reactions with those substrates.

57. Enzymes function as catalysts by

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.

For the reaction A + B--> C + D, the equilibrium constant (Keq) is expressed as

[C][D]/[A][B]

50. The substrate of an enzyme binds at the

active site

Enzyme activity can be controlled by

allosteric regulation, covalent modification and feedback (end product) inhibition.