Enzymes (CH2)

Question 1

List some key points about enzymes?

Answer 1

• Lower Ea
• Increase Reaction Rate
• DO NOT alter equilibrium constant
• Are not changed or consumed
• pH and temperature-sensitive
• DO NOT affect entropy
• Specific

Question 2

Catalyze the transfer of electrons between biological molecules. They often have a cofactor that acts as an electron carrier, such as NAD+ or NADH+.

Answer 2

Oxidoreductases

Question 3

Catalyze the movement of a functional group from one molecule to another. Most will be forwardly named, but remember that kinases are also a member of this class.

Answer 3

Transferases

Question 4

Catalyze the transfer of a phosphate group, generally from ATP to another molecule.

Answer 4

Kinases

Question 5

Catalyze the breaking of a compound into two molecules using the addition of water and includes _____, _____, and _____.

Answer 5

Hydrolases:

• Peptidases
• Nucleases
• Lipases

Question 6

Break down proteins.

Answer 6

Peptidases

Question 7

Break down nucleic acids.

Answer 7

Nucleases

Question 8

Break down lipids.

Answer 8

Lipases

Question 9

Catalyze the cleavage of a single molecule into two products. Also, because most enzymes can also catalyze the reverse of their specific reactions, the synthesis of two molecules into a single molecule may also be catalyzed by this class (labeled differently).

Answer 9

Lyase; Synthase

Question 10

Catalyze the rearrangement of bonds within a molecule. Keep in mind that these catalyzed reactions are between stereoisomers and constitutional isomers. Can also be classified as?

Answer 10

Isomerases:

• Oxidoreductases
• Transferases
• Lyases

Question 11

Catalyze addition or synthesis reactions, generally between molecules and often require ATP. Also most likely to be encountered by nucleic acid synthesis and repair.

Answer 11

Ligases

Question 12

One that requires an energy input (G Change > 0).

Answer 12

Endergonic

Question 13

One in which energy is given off (G Change < 0).

Answer 13

Exergonic

Question 14

Generally inorganic molecules or metal ions and often ingested as dietary minerals.

Answer 14

Cofactors

Question 15

Small organic groups, the vast majority of which are vitamins or derivatives of vitamins such as NAD+, FAD, and “______”- A.

Answer 15

Coenzymes/Prosthetic Groups

Question 16

Enzymes without their cofactors are called?

Answer 16

Apoenzymes

Question 17

Enzymes that contain cofactors (and coenzymes).

Answer 17

Holoenzymes

Question 18

What does this graph indicate?

Answer 18

There is an increased Km and the Vmax has remained the same. Therefore this is competitive inhibition.

Question 19

What does this graph indicate?

Answer 19

The Km and the Vmax have decreased. This is uncompetitive inhibition.

Question 20

What does this graph indicate?

Answer 20

The Km has not changed and the Vmax has decreased. This is noncompetitve inhibition.

Question 21

How do competitive inhibitors bind?

Answer 21

It binds to the active site. The substrate will always out compete the inhibitor.

Question 22

How do noncompetitive inhibitors bind?

Answer 22

It binds to the allosteric site. The inhibitor has equal affinity for the enzyme and the enzyme substrate complex.

Question 23

How do uncompetitive inhibitors bind?

Answer 23

It binds to the allosteric site but also requires that it be an enzyme-substrate complex.

Question 24

How does mixed inhibition work? Explain all.

Answer 24

It has different affinities for enzyme and enzyme-substrate complexes.

• If the inhibitor binds to the enzyme: increases Km.
• If the inhibitor binds to the enzyme-substrate complex : lowers Km.

Vmax always decreases.