Lecture 4: Enzymes

Question 1

What are a few reasons to use proteins as catalysts?

Answer 1

Milder Conditions

Higher reaction rates

Greater reaction specificity

Capacity for regulation

Question 2

Are enzymes globular proteins?

Answer 2

Yes;

Question 3

What are ribozymes

Answer 3

Enzymes that catalyze RNA reactions

Question 4

What is the name of the molecule that is catalyzed?

Answer 4

Substrate

Question 5

True or False; Active site residues also contribute to substrate specificity

Answer 5

True

Question 6

What does ES stand for?

Answer 6

Enzyme- Substrate (Complex)

Question 7

What is the top of the energy hill?

Answer 7

Transition State

Question 8

True or False; Increase in AE (Activation Energy) decreases rate of reaction

Answer 8

True AE/ROR are opposite

Question 9

True or False; enzyme lowers Delta G and decreases reaction rate

Answer 9

False; lower delta G= increase in reaction rate

Question 10

Does the enzyme lower the AE?

Answer 10

Yes;

Question 11

Does the enzyme change the reaction eq.?

Answer 11

No; it does not have effect on the equilibria

Question 12

What is the major difference between the S & P transition state?

Answer 12

Activation Energy

Question 13

What are (3) ways enzymes lower AE?

Answer 13

(1) Rearrange covalent bonds
(2) Bring reactive groups closer
(3) Stabilize transition state

Question 14

What is the rate limiting step?

Answer 14

Step with the highest activation energy

Question 15

What is the formation and decay of transient chemical species?

Answer 15

Reaction Intermediates

Question 16

How do you stabilize the transition state?

Answer 16

Form weak covalent bonds bt. enzyme and substrate to lower activation energy?

Question 17

True or false; Different energies are used to for catalysis and enzyme specificity

Answer 17

False; same energy is used in both.

Question 18

The E-site is used to form a variety of ______ interactions.

Answer 18

Weak interactions

Question 19

What is kinetics?

Answer 19

Study of the rate at which compounds react

Question 20

Are irreversible inhibitors promiscuous?

Answer 20

Yes; they are toxic and bind to anything (sleep with everyone)

Question 21

How are reversible inhibitors used as drugs?

Answer 21

slow down a specific enzyme

Question 22

What are (2) ways in which reversible inhibitors bind?

Answer 22

(1) free enzyme and prevent the binding of the substrate

(2) enzyme-substrate complex and prevent the reaction

Question 23

What are (3) types of inhibition?

Answer 23

(1) Competitive
(2) Uncompetitive
(3) Noncompetitive (mixed)

Question 24

True or false: Kd=Km

Answer 24

True

Question 25

What is 1/Ka?

Answer 25

Kd (disassociation constant)

Question 26

What does Competitive Inhibition bind to?

Answer 26

Active Site of Free Enzyme

Question 27

What is Competitive Inhibition Km & Affinity?

Answer 27

Km increases Affinity decreases

Question 28

What is Competitive Inhibition y-max & Vmax?

Answer 28

stays the same

Question 29

What does Non-Competitive Inhibition bind to?

Answer 29

Active site of the free enzyme ES complex and varying affinity

Question 30

What does Un-Competitive Inhibition bind to?

Answer 30

Allosteric Site of ES Complex

Question 31

What happens to the Km and Affinity of Un-Competitive?

Answer 31

Km- decreases Affinity- Increases

Question 32

What happens to the y-max and v=man of Un-Competitive?

Answer 32

They both decrease

Question 33

What is another name for irreversible inhibitors

Answer 33

Suicide substrate

Question 34

Describe Competitive Inhibition Graph

Answer 34

Lines intersect at y-axis

Question 35

Describe Uncompetitive Inhibition Graph

Answer 35

Lines are parallel

Question 36

What is another name for mixed inhibition

Answer 36

Non-competitive

Question 37

Where does covalent modification occur?

Answer 37

Irreversible Inhibtion

Question 38

Describe Mixed Inhibition Graph

Answer 38

Lines intersect at y-axis

Question 39

What is a protease?

Answer 39

Enzyme that cleaves peptides on the C-terminal side of Aromatic AA's.

Question 40

True or False; Proteases hydrolyze the peptide bond

Answer 40

True

Question 41

What are the three AA that make up the Catalytic Triad

Answer 41

Ser195 His57 ASP102

Question 42

In general base catalysis, what extracts the proton?

Answer 42

Amino Acid extracts the proton

Question 43

In general base catalysis, AA acts as a _____ removing___ from H2).

Answer 43

Base; Proton

Question 44

What is removed from H2O in AA catalysis?

Answer 44

-OH

Question 45

What (2) items must we remember about General-Base Catalysis?

Answer 45

(1) Protein Extraction by a weak base | (2) Typically via groups other than -OH from water

Question 46

What is General Acid Catalysis

Answer 46

AA donates a proton

Question 47

Where is peptidoglycan found?

Answer 47

Cell Walls

Question 48

What type of enzyme is lysozyme?

Answer 48

antibacterial enzyme

Question 49

Dehydration of Lys345 forms what? What enzyme does that

Answer 49

Double Bond; Enolase

Question 50

Use of which inhibitors make the max seem lower when inhibitor is not present

Answer 50

Non-competitive/mixed

Question 51

Use of which inhibitor make the max seem lower when inhibitor is present?

Answer 51

None; max is never high

Question 52

Use of which Inhibitor-affinity of enzyme for substrate increases

Answer 52

Un-Competitive