Bio Chapter 8

exergonic reaction

A chemical reaction that releases energy

induced fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.

chemical energy

potential energy stored in chemical bonds

catabolic pathway

release energy by breaking down complex molecules into simpler compounds

catalyst

something that brings about a change in something else

potential energy

stored energy that results from the position or shape of an object

thermodynamics

study of the flow and transformation of energy in the universe

energy

the ability to do work

catalysis

the acceleration of a reaction rate by a molecule that is unchanged by participating in the reaction

metabolism

the combination of chemical reactions through which an organism builds up or breaks down materials

activation energy

the minimum amount of energy required to start a chemical reaction

phosphorylated intermediate

the recipient with the phosphate group covalently bonded to it

bioenergetics

the study of how energy flows through living organisms

energy coupling

the use of energy released from an exergonic reaction to drive an endergonic reaction

heat

thermal energy in transfer from one body of matter to another

anabolic pathway

consume energy to build complicated molecules from simpler ones

free energy

energy available to do work

1st law of thermodynamics

energy is neither created nor destroyed

kinetic energy

energy of motion

enzyme-substrate complex

enzyme binds to its substrate

coenzyme

organic cofactor

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

substrate

A specific reactant acted upon by an enzyme

As ATP begins to build up in a cell, metabolism slows down. How does this happen? A. ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function. B. ATP binds to the active sites of many of the enzymes involved in metabolism, causing them to stop functioning. C. Excess ATP causes many of the enzymes involved in metabolism to denature. D. None of the listed responses is correct. E. ATP acts as an activator, increasing the rate of its production.

A. ATP acts as an allosteric inhibitor to many of the enzymes involved in metabolism, thus slowing their function.

Which of the following correctly states the relationship between anabolic and catabolic pathways? A. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways. B. Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways. C. Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways. D. Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules. E. The flow of energy between catabolic and anabolic pathways is reversible.

A. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Which of the following statements correctly describes cofactors and coenzymes? A. Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor. B. Both are nonprotein enzyme helpers; but most coenzymes are metal ions, and most cofactors are organic molecules. C. Neither cofactors nor coenzymes assist enzyme function. D. Both cofactors and coenzymes act as allosteric inhibitors to various enzymes. E. Cofactors that are metal ions activate enzymes, but coenzymes deactivate them.

A. Both are nonprotein enzyme helpers; but most cofactors are metal ions, and coenzymes are organic molecules that are a specific type of cofactor.

Which of the following statements is correct regarding competitive and noncompetitive enzyme inhibitors? A. Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site. B. Inhibitors always bind irreversibly to an enzyme. C. Only competitive inhibitors affect enzyme function. D. Neither type of inhibitor affects enzyme function. E. Competitive inhibitors do not bind directly to the active site of an enzyme while noncompetitive inhibitors do.

A. Competitive inhibitors bind to the active site of an enzyme while noncompetitive inhibitors bind to an enzyme away from the active site.

Which of the following statements about enzymes is true? A. Enzymes speed up the rate of the reaction without changing the ΔG for the reaction. B. Enzymes increase the rate of a reaction by raising the activation energy for reactions. C. Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme. D. The more heat that is added to a reaction, the faster the enzymes will function. E. All of the listed responses are correct.

A. Enzymes speed up the rate of the reaction without changing the ΔG for the reaction.

An exergonic reaction __________ free energy, and an endergonic reaction __________ free energy. A. releases; absorbs B. absorbs; releases C. releases; releases D. destroys; creates E. absorbs; absorbs

A. releases; absorbs

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? A. The entropy of the organism's environment must also be decreasing. B. Energy input into the organism must be occurring to drive the decrease in entropy. C. Heat is being used by the organism as a source of energy. D. The first law of thermodynamics is being violated. E. In this situation, the second law of thermodynamics must not apply.

B. Energy input into the organism must be occurring to drive the decrease in entropy.

What would the value of ΔS be for a chemical reaction in which a molecule is broken down into smaller components? A. Zero B. Positive C. Negative D. Neutral

B. Positive

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? A. Cellular respiration releases some energy as heat. B. The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water. C. All types of cellular respiration produce ATP. D. All of the listed responses are correct. E. None of the listed responses is correct.

B. The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

At low pH, a particular enzyme catalyzes a reaction at a high rate. At neutral pH, the enzyme is completely inactive. What statement best explains the difference in how pH affects the function of this enzyme? A. Low pH causes the enzyme to denature, and neutral pH causes the enzyme to function normally. B. The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional. C. The enzyme functions best at both low and neutral pH. D. Neutral pH provides the optimal environment in which this enzyme functions. E. pH has no effect on enzyme function.

B. The enzyme is adapted for low pH but is denatured at neutral pH, leaving it nonfunctional.

In general, the hydrolysis of ATP drives cellular work by __________. A. changing to ADP and phosphate B. releasing free energy that can be coupled to other reactions C. acting as a catalyst D. lowering the free energy of the reaction E. releasing heat

B. releasing free energy that can be coupled to other reactions

How does ATP drive mechanical work inside a cell? A. By phosphorylating a transport protein B. By removing a phosphate from a transport protein C. By binding to motor proteins D. By providing free energy to facilitate the formation of polymers from monomers E. By removing free energy from a chemical reaction

C. By binding to motor proteins

How does ATP drive transport work inside a cell? A. By removing free energy from a chemical reaction B. By providing free energy to facilitate the formation of polymers from monomers C. By phosphorylating a transport protein D. By binding to motor proteins E. By removing a phosphate from a transport protein

C. By phosphorylating a transport protein

Which of the following statements about enzyme function is correct? A. Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the activation energy. B. Enzymes can change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the net energy output. C. Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output. D. Enzymes can greatly speed up reactions, but they cannot change the activation energy because they cannot change the net energy output. E. None of the listed responses is correct.

C. Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Which of the following statements is correct regarding kinetic and potential energy? A. None of the listed responses is correct. B. Potential energy is related to the relative motion of objects, and kinetic energy is the energy that matter possesses because of its location or structure. C. Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure. D. Potential energy cannot be converted to kinetic energy. E. Chemical energy is a type of kinetic energy, and thermal energy is a type of potential energy.

C. Kinetic energy is associated with the relative motion of objects, and potential energy is the energy that matter possesses because of its location or structure.

Which of the following is true regarding metabolic pathways? A. Each reaction in the pathway is catalyzed by the same enzyme. B. Metabolic pathways consist of a single chemical reaction. C. Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme. D. Metabolic pathways are not important to a cell's ability to function. E. Metabolic pathways consist of only anabolic pathways.

C. Metabolic pathways consist of a series of reactions, each catalyzed by a different enzyme.

Which of the following statements about the active site of an enzyme is correct? A. The active site has a fixed structure (shape). B. Coenzymes are rarely found in the active site of an enzyme. C. The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits. D. The structure of the active site is not affected by changes in temperature. E. The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme.

C. The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

Cells use ATP constantly, but ATP is considered a renewable resource. What process makes this possible? A. ADP is generated by the addition of a phosphate group to ATP. B. The hydrolysis of ATP is an irreversible reaction. C. ADP and ATP are stored in large amounts in a cell. D. ATP can be regenerated by the addition of a phosphate group to ADP. E. None of the listed responses is correct.

D. ATP can be regenerated by the addition of a phosphate group to ADP.

At low temperatures, a particular enzyme catalyzes a reaction, but at a slow rate. At high temperatures, the enzyme is completely inactive. What statement best explains the difference in how temperature affects the function of this enzyme? A. The enzyme functions best at both low and high temperatures. B. Temperature has no effect on enzyme function. C. High temperature provides the optimal environment in which this enzyme functions. D. At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional. E. Low temperatures cause the enzyme to denature, and high temperatures cause the enzyme to move too fast to bind to its substrate.

D. At low temperatures, there is not enough free energy for the enzyme to function at a high rate, and at high temperatures, the enzyme is denatured, leaving it nonfunctional.

Which of the following reactions would be endergonic? A. All of the listed responses are correct. B. HCl → H+ + Cl C. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O D. Glucose + fructose → sucrose E. ATP → ADP + Pi

D. Glucose + fructose → sucrose

Which of the following is changed by the presence of an enzyme in a reaction? A. The magnitude of ΔG B. The G value for the reactants C. The sign of ΔG D. The activation energy E. The G value for the products

D. The activation energy

What best characterizes the role of ATP in cellular metabolism? A. The ΔG associated with its hydrolysis is positive. B. It is catabolized to carbon dioxide and water. C. The release of free energy during the hydrolysis of ATP heats the surrounding environment. D. The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate. E. The charge on the phosphate group of ATP tends to make the molecule very water-soluble.

D. The free energy released by ATP hydrolysis that may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of __________. A. feedback inhibition B. competitive inhibition C. noncompetitive inhibition D. allosteric regulation E. cooperativity

D. allosteric regulation

An exergonic (spontaneous) reaction is a chemical reaction that __________. A. is common in anabolic pathways B. cannot occur outside of a living cell C. occurs only when an enzyme or other catalyst is present D. releases energy when proceeding in the forward direction E. leads to a decrease in the entropy of the universe

D. releases energy when proceeding in the forward direction

Which of the following states the relevance of the first law of thermodynamics to biology? A. Energy is destroyed as glucose is broken down during cellular respiration. B. The total energy taken in by an organism must be greater than the total energy stored or released by the organism. C. Photosynthetic organisms produce energy in sugars from sunlight. D. Living organisms must increase the entropy of their surroundings. E. Energy can be freely transformed among different forms as long as the total energy is conserved.

E. Energy can be freely transformed among different forms as long as the total energy is conserved.

The primary manner in which cells manage their energy resources in order to do work is called energy coupling. Which of the following statements accurately defines energy coupling? A. Endergonic reactions drive exergonic reactions. B. Chemical reactions in cells are always at equilibrium. C. Endergonic and exergonic reactions occur independently of each other. D. Anabolic reactions drive catabolic reactions. E. Exergonic reactions drive endergonic reactions.

E. Exergonic reactions drive endergonic reactions.

endergonic reaction

Reaction that absorbs free energy from its surroundings.

Which of these statements about enzyme inhibitors is true? A. Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory. B. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback. C. A noncompetitive inhibitor does not change the shape of the active site. D. A competitive inhibitor binds to the enzyme at a place that is separate from the active site. E. The action of inhibitors may be reversible or irreversible.

E. The action of inhibitors may be reversible or irreversible.

Which of the following statements is correct regarding ATP? A. ATP cannot transfer energy to other molecules. B. ATP molecules do not release free energy when hydrolyzed. C. The energy in an ATP molecule is released from the ribose group. D. The energy in an ATP molecule is released from the adenine group. E. The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.

E. The energy in an ATP molecule is released through hydrolysis of one of the phosphate groups.

ATP allosterically inhibits enzymes in ATP-producing pathways. The result of this is called __________. A. positive feedback B. competitive inhibition C. cooperativity D. denaturing E. feedback inhibition

E. feedback inhibition

Enzyme activity is affected by pH because __________. A. most substrates don't function well at high or low pH B. low pH will denature all enzymes C. changes in pH can cause loss of cofactors from the enzyme D. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier E. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

E. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

cooperativity

It amplifies the response of enzymes to substrates.

2nd law of thermodynamics

The principle whereby every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.

thermal energy

The total energy of motion in the particles of a substance

entropy

a measure of the disorder of a system

spontaneous process

a process that can occur without an input of energy

active site

a region on an enzyme that binds to a protein or other substance during a reaction.

enzyme

a substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction.

feedback initiation

also called negative feedback - the process in which a stimulus produces a response that opposes the original stimulus

noncompetitve inhibitors

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

competitive inhibitors

bind to the active site of an enzyme, competing with the substrate

cofactors

nonprotein enzyme helpers