CH.6 METABOLISM

Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?

-y phosphate (the terminal phosphate)

In cells, what is usually the immediate source of energy for an endergonic reaction?

ATP

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

What will happen to the rates of the forward and reverse reactions when a catalyst is added?

Both forward and reverse rates increase. The Haber process can be cheaply catalyzed using porous iron. A much more effective catalyst for the Haber process is osmium; however, it is very expensive and toxic.

Which of the following statements regarding enzymes is true?

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

Which of the following is true of enzymes?

Enzymes increase the rate of chemical reaction by lowering activation energy barriers.

What is the fate of the phosphate group that is removed when ATP is converted to ADP?

It is acquired by a reactant in an endergonic reaction.

According to the induced fit hypothesis of enzyme catalysis, which of the following is correct?

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

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?

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

For living organisms, which of the following is an important consequence of the first law of thermodynamics?

The organism ultimately must obtain all of the necessary energy for life from its environment.

Which of the following statements is true about enzyme-catalyzed reactions?

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

The Haber process is typically carried out at a temperature of approximately 500∘C. What would happen to the rate of the forward reaction if the temperature were lowered to 100∘C?

The reaction rate would decrease .

What would happen to the rate of the forward reaction if the concentration of nitrogen were decreased?

The reaction rate would decrease. As the concentration of nitrogen decreases, collisions between nitrogen and hydrogen are less likely to occur.

Which of these is exhibiting kinetic energy?

a space station orbiting Earth

trans

across

Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's

activation energy.

4. The competitive inhibitor competes with the substrate for the ____________ on the enzyme.

active site

6. A substrate binds to an enzyme at the ________ , where the reaction occurs.

active site

Which of the following is most similar in structure to ATP?

an RNA nucleotide

2. An enzyme is considered a _____ because it speeds up chemical reactions without being used up.

catalyst

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

cellular respiration

-trop-

change, turn, move

4. A ______ , such as a vitamin, binds to an enzyme and plays a role in catalysis.

cofactor

1. A (n) ____________ inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate.

competitive

5. When properly aligned, the enzyme and substrate form an enzyme-substrate (ES) ____________

complex

1. An enzyme is ________d when it loses its native conformation and its biological activity.

denatured

The reaction ADP + P --> ATP is a(n) _____ reaction.

endergonic

Which of these reactions requires a net input of energy from its surroundings?

endergonic

A chemical reaction that has a positive ΔG is best described as

endergonic.

"Conservation of energy" refers to the fact that _____.

energy cannot be created or destroyed but can be converted from one form to another

Whenever energy is transformed, there is always an increase in the

entropy of the universe.

-ase

enzyme

5. When the noncompetitive inhibitor is bonded to the enzyme, the shape of the ___________ is distorted.

enzyme

A(n) _____ reaction occurs spontaneously.

exergonic

Part complete The following reaction A --> B + C + heat is a(n) _____ reaction.

exergonic

The energy for an endergonic reaction comes from a(n) _____ reaction.

exergonic

Select the INCORRECT association.

exergonic ... uphill

therm-

heat

Which of these are by-products of cellular respiration?

heat, carbon dioxide, and water

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?

hydrolysis

Which of the following would increase the rate of the reverse reaction?

increasing the concentration of ammonia. The concentration of NH3 affects how quickly N2 and H2 can be made.

3. Usually, a(n) ____________ 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

An enzyme _____.

is an organic catalyst

As a result of its involvement in a reaction, an enzyme _____.

is unchanged

lac- (or lact-)

milk

kin- (or kinet-)

moving

2. A (n) _________________ inhibitor binds to a site on the enzyme that is not the active site.

noncompetitive

allo

other

extra-

outside of

Chemical energy is a form of _____ energy.

potential

In general, enzymes are what kinds of molecules?

proteins

Enzymes work by _____.

reducing EA

3. An enzyme is considered __________ because of its ability to recognize the shape of a particular molecule.

specific

6. Enzyme inhibitors disrupt normal interactions between an enzyme and its ____________ .

substrate

7. In a catalyzed reaction a reactant is often called a _________ .

substrate

What name is given to the reactants in an enzymatically catalyzed reaction?

substrate

glyc-

sweet (sugar)

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because

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

What is energy coupling?

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

sub-

under, below