Biochemistry Chapter 2: Enzymes

Question 1

What are enzymes?

Answer 1

Enzymes are biological catalysts that are unchanged by the reactions they catalyze and are reusable

Question 2

What are oxidoreductases?

Answer 2

Catalyze oxidation-reduction reactions that involve the transfer of elections.

Question 3

What are transferases?

Answer 3

Transferases move a functional group from one molecule to another molecule.

Question 4

What are hydrolases?

Answer 4

They catalyze cleavage with the addition of water.

Question 5

What are lyases?

Answer 5

They catalyze cleavage without the addition of water and without transfer of electrons. The reverse reaction is often more important biologically.

Question 6

What are isomerases?

Answer 6

They catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers.

Question 7

What are ligases?

Answer 7

Join two large biomolecules, often of the same type.

Question 8

Exergonic reactions____energy

Endergonic reactions____energy

Answer 8

Exergonic reactions release energy.

Endergonic reactions absorb energy.

Question 9

What do enzymes change about a reaction?

Answer 9

The rate at which equilibrium is reached, not the free energy or enthalpy.

Question 10

How do enzymes act?

Answer 10

They stabilize the transition state by providing a favorable environment or bonding with the substrate

Question 11

What does the lock and key theory hypothesize?

Answer 11

The lock and key theory hypothesizes that the enzyme and substrate are exactly complementary.

Question 12

What does the induced fit model hypothesize?

Answer 12

enzyme and substrate undergo conformational changes to interact fully.

Question 13

What are two molecules that enzymes can use?

Answer 13

metal cation COFACTORS or organic COENZYMES

Question 14

What is saturation kinetics?

Answer 14

As the substrate concentration increases, the reaction rate does as well until a maximum value is reached.

Question 15

What do cooperative enzymes show in their curve?

Answer 15

They show a sigmoidal curve because of the change in activity with substrate binding.

Question 16

What can impact proteins’ ability to function?

Answer 16

temperature, pH and solution concentration

Question 17

What is feedback inhibition?

Answer 17

a regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the pathway

Question 18

What is reversible inhibition?

Answer 18

ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment.
(competitive, noncompetitive, mixed, uncompetitive)

Question 19

What is competitive inhibition? What does it do to the Vmax/Km?

Answer 19

Inhibitor is similar to the substrate and binds at the active site. It can be overcome by adding more substrate. Vmax does not change, Km increases.

Question 20

What is noncompetitive inhibition?

Answer 20

Inhibitor binds with equal affinity to the enzyme and enzyme-substrate complex. Vmax decreases and Km is unchanged.

Question 21

What is mixed inhibition?

Answer 21

when the inhibitor binds with unequal affinity to the enzyme and the enzyme-substrate complex. Vmax is decreased and Km is increased or decreased depending on which the inhibitor has a high affinity for.

Question 22

What is uncompetitive inhibition?

Answer 22

When it only binds to the enzyme-substrate complex. Both Km and Vmax decrease.

Question 23

What is irreversible inhibition?

Answer 23

Alters the enzyme in a way that the active site is unavailable for a prolonged duration or permanently; new enzyme molecules must be synthesized for the reaction to occur again.

Question 24

Allosteric sites?

Answer 24

Where things other than substrate bind

Question 25

What are zymogens?

Answer 25

precursors that are inactive & are activated by cleavage.