Ch 6 Enzymes: The Catalysts of Life

In a graph of reaction rate vs substrate concentration, at what point does the reaction rate remains constant?

-when saturation point happens, the point where there is a high substrate concentration -when the hyperbola is a horizontal line

what happens to enzymes as the substrate concentration increases?

As the concentration of substrate increases, the reaction rate increases, until the point where the active site is saturated with substrate.

what is the action of irreversible inhibitors and why?

Because they bind directly to the active site by covalent bonds, irreversible inhibitors permanently render an enzyme inactive.

how many active sites are found in an enzyme? what happens here?

In general, an enzyme has one active site at which catalysis can occur. When the substrates are bound to the active site, the enzyme will catalyze the reaction.

why an enzyme is so specific?

Its three-dimensional shape allows it to act only on specific molecules,

substrate

The reactant on which an enzyme works

active site

The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.

Which of the following is an example of a prosthetic group? a zinc ion a glycine residue a nickel catalyst a polypeptide chain carboxypeptidase A

a zinc ion

Enzymes work by _____. a) increasing the potential energy difference between reactant and product b) reducing EA c) adding energy to a reaction d) adding a phosphate group to a reactant e) decreasing the potential energy difference between reactant and product

b) reducing EA

Which of the following is an enzyme? iron N-acetylmuramic acid carboxypeptidase A histidine ATP

carboxypeptidase A

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's a. endothermic level. b. free-energy content. c. entropy. d. equilibrium point. e. activation energy.

e. activation energy.

when saturation is reached, the reaction rate is independent of what?

he reaction rate is independent of substrate concentration.

a_inhibitor binds to a site on the enzyme that is not the active site

noncompetitive

What name is given to the reactants in an enzymatically catalyzed reaction? products EA active sites substrate reactors

substrate

enzyme inhibitors disrupt normal interactions between an enzyme and its_

substrate

The Michaelis constant, Km, refers to the __________ at which a reaction proceeds at __________ of the maximum velocity. This constant most accurately reflects __________. product concentration; one-half; structure of the substrate substrate concentration; one-half; the affinity of the substrate-enzyme interaction substrate concentration; one-fourth; pH optimum of the enzyme enzyme concentration; one-half; temperature optimum of the enzyme

substrate concentration; one-half; the affinity of the substrate-enzyme interaction

how can you decrease the effect of the competitive inhibitors?

they can be outcompeted by adding extra substrate

an enzyme is_(selective vs nonselective)

very selective

how specific is the enzyme? what this implies within the body?

-Because of the specific fit between enzyme and substrate, each enzyme can catalyze only one kind of reaction involving specific substrates. -Thousands of different enzymes may be required to carry out all of a cell's metabolic processes.

what is an example of competitive inhibitors?

-Most medications are enzyme inhibitors of one kind or another. -drugs like antibiotic penicillin (which inhibits an enzyme involved in bacterial cell-wall synthesis) and aspirin (which inhibits cyclooxygenase-2, the enzyme involved in the inflammatory reaction)

what are the two types of reversible enzyme inhibitors?

-competitive -non-competitive

In a graph of reaction rate vs substrate concentration, In which region is the enzyme saturated with substrate?

-in the region where there is a high substrate concentration and the hyperobola begins to be a horizonal line

what are the 2 classifications of enzyme inhibitors?

-irreversible -reversible

An enzyme _____. is a source of energy for endergonic reactions can bind to nearly any molecule is an organic catalyst is a inorganic catalyst increases the EA of a reaction

-is an organic catalyst -Enzymes are proteins that behave as catalysts.

How does a living cell overcome the energy barrier so that its metabolic reactions can occur quickly and precisely?

A special kind of protein called an enzyme is the answer.

exergonic reaction

A spontaneous chemical reaction, in which there is a net release of free energy.

Phosphoenolpyruvate (PEP) is considered an unstable molecule, whereas ATP is considered a metastable molecule. Which of the following is likely true about the nonenzymatic hydrolysis of PEP and the hydrolysis of ATP? The hydrolysis of ATP and PEP will occur spontaneously and quickly. The hydrolysis of ATP will be spontaneous and fast, whereas the hydrolysis of PEP will be nonspontaneous. The hydrolysis of ATP and PEP will be nonspontaneous. The hydrolysis of ATP and PEP will be spontaneous, but the hydrolysis of ATP will be much slower than the hydrolysis of PEP.

ATP and PEP will be spontaneous, but the hydrolysis of ATP will be much slower than the hydrolysis of PEP.

You have an enzymatic reaction proceeding at the optimum pH and optimum temperature. You add a competitive inhibitor to the reaction and notice that the reaction slows down. What can you do to speed the reaction up again? Add more inhibitor to speed up the reaction. Add more substrate; it will outcompete the inhibitor and increase the reaction rate. Increase the temperature. Increase the pH.

Add more substrate; it will outcompete the inhibitor and increase the reaction rate.

An enzyme serves as a _(role), _(doing what) without _(what happens to it during reaction). An enzyme does not _(what does not do to make a reaction to happen); instead, it _(what it does to make a reaction to happen)

An enzyme serves as a biological catalyst, increasing the rate of a reaction without being changed into a different molecule. An enzyme does not add energy to a reaction; instead, it speeds up a reaction by lowering the energy barrier.

how can you decrease the effect of competitive inhibitors?

Competitive inhibition can be overcome by adding more substrate to outcompete the inhibitor.

what competitive inhibitors do?

Competitive inhibitors compete physically and structurally with the substrate for an enzyme's active site

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule? A. dehydration decomposition B. entropic C. dehydration synthesis D. hydrolysis E. anabolism

D. hydrolysis

Enzymes work by _____. increasing the potential energy difference between reactant and product decreasing the potential energy difference between reactant and product adding energy to a reaction reducing EA adding a phosphate group to a reactant

Enzymes work by reducing the energy of activation.

If exergonic reactions occur spontaneously, what keeps molecules from breaking apart and cell chemistry from racing out of control? (include what happens within the reaction to make it happen)

For any reaction to occur, even a downhill reaction, some energy must be added to get the reaction going. This energy is needed to break bonds in the reactant molecules. The energy needed to start a chemical reaction is called the energy of activation (EA). This required energy input represents a barrier that prevents even energy-releasing exergonic reactions from occurring without some added energy.

Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction? Increase the pH. Increase the temperature. Increase the enzyme concentration. Increase the substrate concentration.

Increase the enzyme concentration.

what irreversible inhibitors do?

Irreversible inhibitors bind directly to the active site by covalent bonds, which change the structure of the enzyme and inactivate it permanently

Why is the Lineweaver-Burk plot important in enzyme kinetics? It illustrates enzyme specificity. It makes it easier to determine Vmax. It is a single-reciprocal plot. It is nonlinear. It reveals the presence of prosthetic groups in enzymes.

It makes it easier to determine Vmax.

A competitive inhibitor will affect the ________ of an enzymatic reaction. S V max P K m K m and V max

K m

enzyme inhibitors.

Molecules other than substrates bind to enzymes. Some of these other molecules slow down the rate of the enzymatic reaction.

what noncompetitive inhibitors do?

Noncompetitive inhibitors do not compete for the active site, but inhibit the enzyme by binding elsewhere and changing the enzyme's shape

a hypothetical enzymatic pathway with four enzymes, labeled E1, E2, E3, and E4. The enzymes make products, labeled P0, P1, P2, P3, and P4. Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown? Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown? P0 binds E4 and activates it. P2 binds E2 and activates it. P4 binds E1 and deactivates it. P3 binds E2 and activates it P4 binds E3 and deactivates it.

P4 binds E1 and deactivates it.

what must be overcome in order for a reaction to proceed?

The energy of activation must be overcome in order for a reaction to proceed.

You have added an irreversible inhibitor to a sample of enzyme and substrate. At this point, the reaction has stopped completely. What can you do to regain the activity of the enzyme? Removing the irreversible inhibitor should get the reaction working again. The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity. Adding more substrate will increase the rate of reaction. Adding more inhibitor should get the reaction up to speed again.

The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.

Which of the following best describes a metastable state? This state is composed of the difference in activation energy of a catalyzed versus an uncatalyzed reaction. The metastable state is created by the prosthetic group of the enzyme. The metastable state is formed by transient complexes with the substrate. This state changes the position of the equilibrium but not the rate. The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.

The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.

An enzyme contains a catalytic histidine residue in its active site that must release an R group proton to solution in order to facilitate catalysis by the enzyme. Which of the following environmental conditions would be required for optimal enzyme activity? [explain] The pH of the environment should be relatively high. The pH of the environment should be relatively low. The pH of the environment would not matter. The environment should be set to the biochemical standard state.

The pH of the environment should be relatively high. reason: histidine (His) is a polar, charged amino acid (hydrophilic) and it one of the 3 basic amino acids

the methods that create the molecules within the body contain what?

These small molecules are often produced in enzymatic pathways that have three or more enzymes making modifications to the substrate.

A noncompetitive inhibitor will affect the ________ of an enzymatic reaction. S P K m V max K m and V max

V max

what happens to the rate of a reaction involving an enzyme when saturation is reached?

When the enzyme is saturated, the rate of the reaction will not increase with the concentration of substrates.

Which of the following statements regarding enzymes is true? a) Enzymes increase the rate of a reaction. b) Enzymes change the direction of chemical reactions. c) Enzymes decrease the free energy change of a reaction. d) Enzymes prevent changes in substrate concentrations. e) Enzymes are permanently altered by the reactions they catalyze.

a) Enzymes increase the rate of a reaction.

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

a) breaking the bond between glucose and fructose and forming new bonds from the atoms of water.

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add more of the enzyme. b. heat the solution to 90°C. c. add more substrate. d. add a noncompetitive inhibitor. e. add an allosteric inhibitor.

a. add more of the enzyme.

Whenever energy is transformed, there is always an increase in the a. entropy of the universe. b. enthalpy of the universe. c. entropy of the system. d. free energy of the system. e. free energy of the universe.

a. entropy of the universe.

the competitive inhibitor competes with the substrate for the_on an enzyme

active site

The site on an enzyme that will bind the substrate is called the activation site. active site. catalyst. metastable site. prosthetic group.

active site.

Covalent modification affects the activity of an enzyme by adding or removing a chemical group. produces modifications that can sometimes be reversed. can involve the addition of phosphate groups. can activate an enzyme. all of the above

all of the above

Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as __________ is to __________. a) work; energy b) exergonic; endergonic c) exergonic; spontaneous d) entropy; enthalpy e) free energy; entropy

b) exergonic; endergonic

In general, enzymes are what kinds of molecules? a) nucleic acids b) proteins c) lipids d) carbohydrates d) minerals

b) proteins

Which of the following statements describes enzyme cooperativity? a. Several substrate molecules can be catalyzed by the same enzyme. b. A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits. c. A product of a pathway serves as a competitive inhibitor of an early enzyme in the pathway. d. A substrate binds to an active site and inhibits cooperation between enzymes in a pathway. e. A multienzyme complex contains all the enzymes of a metabolic pathway.

b. A substrate molecule bound to an active site of one subunit promotes substrate binding to the active site of other subunits.

Which of the following statements regarding enzymes is true? a. Enzymes increase the rate of a reaction by making the reaction more exergonic. b. Enzymes increase the rate of a reaction by lowering the activation energy barrier. c. Enzymes change the equilibrium point of the reactions they catalyze. d. Enzymes make the rate of a reaction independent of substrate concentrations. e. Enzymes increase the rate of a reaction by reducing the rate of reverse reactions.

b. Enzymes increase the rate of a reaction by lowering the activation energy barrier.

Which of the following is NOT a way in which an enzyme can speed up the reaction that it catalyzes? a. The active site of the enzyme can provide a microenvironment with a different pH that facilitates the reaction. b. The active site can provide heat from the environment that raises the energy content of the substrate. c. Binding of the substrate to the active site can stretch bonds in the substrate that need to be broken. d. The enzyme binds a cofactor that interacts with the substrate to facilitate the reaction. e. The binding of two substrates in the active site provides the correct orientation for them to react to form a product.

b. The active site can provide heat from the environment that raises the energy content of the substrate. An enzyme cannot extract heat from the environment to speed a reaction. It can only lower the activation energy barrier so that more substrates have the energy to react.

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

b. The binding of the substrate changes the shape of the enzyme's active site.

Which of the following is true for all exergonic reactions? a. The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. b. The reaction proceeds with a net release of free energy. c. A net input of energy from the surroundings is required for the reactions to proceed. d. The products have more total energy than the reactants. e. The reactions are rapid.

b. The reaction proceeds with a net release of free energy.

An enzyme changes the position of the equilibrium of the reaction. is always a protein. does not change the rate at which the equilibrium is achieved. binds substrates in a manner that facilitates the formation of product. decreases the rate of a reaction.

binds substrates in a manner that facilitates the formation of product.

How can one increase the rate of a chemical reaction? a) Decrease the concentration of the reactants. b) Cool the reactants. c) Add a catalyst. d) Increase the entropy of the reactants. e) Increase the activation energy needed.

c) Add a catalyst.

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell? a) It can be added to water and excreted as a liquid. b) It can be added to other molecules in order to activate them. c) It can only be used to regenerate more ATP. d) It can enter the nucleus to affect gene expression. e) It is released as an excretory waste.

c) It can only be used to regenerate more ATP.

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule? a) entropic b) anabolism c) hydrolysis d) dehydration synthesis e) dehydration decomposition

c) hydrolysis

An enzyme _____. a) is a source of energy for endergonic reactions b) increases the EA of a reaction c) is an organic catalyst d) is a inorganic catalyst e) can bind to nearly any molecule

c) is an organic catalyst

Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions? a) α -phosphate (the phosphate closest to ribose) b) β-phosphate (the middle phosphate) c) γ-phosphate (the terminal phosphate) d) adenine group e) ribose sugar

c) γ-phosphate (the terminal phosphate)

Which of the following is a statement of the first law of thermodynamics? a. Kinetic energy is stored energy that results from the specific arrangement of matter. b. Energy cannot be transferred or transformed. c. Energy cannot be created or destroyed. d. The entropy of the universe is constant. e. The entropy of the universe is decreasing.

c. Energy cannot be created or destroyed.

Which of the following statements about feedback regulation of a metabolic pathway is correct? a. The enzyme that is regulated by feedback inhibition is usually the last enzyme in the metabolic pathway. b. The products of the pathway become the reactants for a different reaction, and thus products are unable to accumulate. c. The final product of a metabolic pathway is usually the compound that regulates the pathway. d. The compound that regulates the pathway acts as a competitive inhibitor or a positive allosteric regulator. e. Accumulation of the product of the pathway increases further formation of that product.

c. The final product of a metabolic pathway is usually the compound that regulates the pathway. It is quite common that the end product of the pathway controls the overall rate of the pathway

The active site of an enzyme is the region that a. binds noncompetitive inhibitors of the enzyme. b. binds allosteric regulators of the enzyme. c. is involved in the catalytic reaction of the enzyme. d. is inhibited by the presence of a coenzyme or a cofactor.

c. is involved in the catalytic reaction of the enzyme.

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because a. the hydrolysis of starch to sugar is endergonic. b. the starch solution has less free energy than the sugar solution. c. the activation energy barrier for this reaction cannot easily be surmounted at room temperature. d. starch hydrolysis is nonspontaneous. e. starch cannot be hydrolyzed in the presence of so much water.

c. the activation energy barrier for this reaction cannot easily be surmounted at room temperature.

Some bacteria are metabolically active in hot springs because a. they are able to maintain a lower internal temperature. b. they use molecules other than proteins or RNAs as their main catalysts. c. their enzymes have high optimal temperatures. d. high temperatures make catalysis unnecessary. e. their enzymes are completely insensitive to temperature.

c. their enzymes have high optimal temperatures.

The Michaelis constant can be determined using the Lineweaver-Burk plot. is equal to twice the V max. is equal to the substrate concentration at V max/2. can be determined using the Lineweaver-Burk plot and is equal to the substrate concentration at V max/2. can be determined using the Lineweaver-Burk plot, is equal to twice the V ma, and is equal to the substrate concentration at V max/2.

can be determined using the Lineweaver-Burk plot and is equal to the substrate concentration at V max/2.

A competitive inhibitor binds to and inactivates the substrate. does not inhibit enzyme activity but does lower substrate concentration. irreversibly binds and inactivates the enzyme. cannot be processed by the enzyme. binds at a site other than the active site.

cannot be processed by the enzyme.

A _inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate

competitive inhibitor

Why is ATP an important molecule in metabolism? a) Its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy. b) Its hydrolysis provides an input of free energy for exergonic reactions. c) Its terminal phosphate bond has higher energy than the other two. d) It provides energy coupling between exergonic and endergonic reactions. e) Its hydrolysis provides an input of free energy for exergonic reactions, it provides energy coupling between exergonic and endergonic reactions, its terminal phosphate group contains a strong covalent bond that when hydrolyzed releases free energy, and its terminal phosphate bond has higher energy than the other two.

d) It provides energy coupling between exergonic and endergonic reactions.

A chemical reaction that has a positive ΔG is correctly described as a) exothermic. b) spontaneous. c) endothermic. d) endergonic. e) enthalpic.

d) endergonic.

Substrate activation may involve (4)

donation of protons to the enzyme. a change in enzyme conformation induced by substrate binding. formation of temporary covalent bonds. accepting protons from the enzyme.

Which of the following is true for all exergonic reactions? a) A net input of energy from the surroundings is required for the reactions to proceed. b) Some reactants will be converted to products. c) The reactions are nonspontaneous. d) The products have more total energy than the reactants. e) The reaction proceeds with a net release of free energy.

e) The reaction proceeds with a net release of free energy.

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? a) anabolism b) catabolism c) dehydration d) metabolism e) catalysis

e) catalysis

Which of the following statements is true about enzyme-catalyzed reactions? a. Enzyme-catalyzed reactions release more free energy than noncatalyzed reactions. b. The free energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme. c. Enzyme-catalyzed reactions require energy to activate the enzyme. d. The reaction always goes in the direction toward chemical equilibrium. e. The reaction is faster than the same reaction in the absence of the enzyme.

e. The reaction is faster than the same reaction in the absence of the enzyme.

Which of the following is (are) true for anabolic pathways? a. They release energy as they degrade polymers to monomers. b. They consume energy to decrease the entropy of the organism and its environment. c. They are usually highly spontaneous chemical reactions. d. They do not depend on enzymes. e. They consume energy to build up polymers from monomers.

e. They consume energy to build up polymers from monomers.

Enzymes are described as catalysts, which means that they _____. a. can alter the free energy change (ΔG) for a chemical reaction b. are proteins c. increase the free energy of the reactants to make the reaction go faster d. provide activation energy for the reactions they facilitate e. increase the rate of a reaction without being consumed by the reaction

e. increase the rate of a reaction without being consumed by the reaction

feedback inhibition is also known as_

end-product inhibition.

when the noncompetitive inhibitor is bonded to the enzyme, the shape of the _is distorted

enzyme

The phosphorylation of glucose to generate glucose-6-phosphate is catalyzed by the enzyme hexokinase. This enzyme, however, is allosterically inhibited by its own product, glucose-6-phosphate. This is an example of __________. covalent modification competitive inhibition feedback regulation irreversible inhibition

feedback regulation

The induced-fit model involves a conformational change in the shape of the enzyme. was proposed by Hans Buchner. proposes that very strong covalent bonds are formed upon substrate binding. states that enzyme-substrate interactions are rigid. is also called the lock-and-key model.

involves a conformational change in the shape of the enzyme.

The active site for carboxypeptidase is formed by the interaction of two polypeptide chains. contains a glutamate residue at position 69. involves only 6 out of a total of 307 amino acids. contains amino acids that are contiguous to one another along the primary sequence of the protein. uses iron as the prosthetic group.

involves only 6 out of a total of 307 amino acids.

usually, an _inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalytic activity

irreversible

As a result of its involvement in a reaction, an enzyme _____. is used up loses energy loses a phosphate group permanently alters its shape. is unchanged

is unchanged

In a graph of energy vs reactants and products, what part of the parabola is found the energy of activation?

it is found between the reactant and the top or cuspid of the curve

Enzymes that catalyze the phosphorylation of other enzymes are __________. Enzymes that catalyze the phosphorylation of other enzymes are __________. ligases oxidoreductases protein kinases phosphoprotein phosphatases

protein kinases

In general, enzymes are what kinds of molecules? proteins minerals carbohydrates lipids nucleic acids

proteins

explain in general sense what the enzyme does to make a reaction to happen (include interaction with substrate and amount of energy needed)

s the substrates bind to the enzyme's active site, they are held in a position that facilitates the reaction. This takes less activation energy than the unaided reaction. Products form and are released. The enzyme emerges unchanged from the reaction.

Enzyme regulation may occur by several methods. Which of the following is not a means of enzyme regulation? saturation allosteric regulation substrate-level phosphorylation covalent modification feedback inhibition

saturation

An enzyme is active in the stomach of an animal but quickly loses its activity when it leaves the stomach. This example illustrates that enzymes are sensitive to changes in pH. inactivated by inhibitors in the small intestine. inactivated by movement. consumed by the quantities of substrate in the small intestine. specific to the organs in which they are produced.

sensitive to changes in pH.

Saturation can be defined as a characteristic of all uncatalyzed reactions. denaturation of an enzyme. the inability to increase reaction velocity beyond a finite upper limit. inhibition of enzyme function by blocking the active site. the substrate concentration at which velocity reaches one-half maximum velocity.

the inability to increase reaction velocity beyond a finite upper limit.

As new enzymes are discovered, the EC system for naming enzymes is to be used. The names are to be based on which of the following criteria? the size of the enzyme a description of substrate function the six major classes of enzyme function an indication of the size of the substrate the name of the substrate

the six major classes of enzyme function

The expression kcat can be described as __________. The expression kcat can be described as __________. the initial velocity of an enzyme the reaction rate the substrate turnover number the Michaelis constant

the substrate turnover number

A plot of enzyme velocity against temperature for an enzyme indicates little activity at 0 degrees Celsius and 40 degrees Celsius, with peak activity at 35 degrees Celsius. The most reasonable explanation for the low velocity at 0 degrees Celsius is that __________. the enzyme was denatured at this temperature substrate binding at the active site is thermodynamically unfavorable at low temperature there is too little activation energy available from the environment the hydrogen bonds that define the enzyme's active site are broken as temperature increases

there is too little activation energy available from the environment

An enzyme influences the structure of which of the following? cofactor intermediate transition state substrate product

transition state