Chapter 7

Question 1

Apoenzyme

Answer 1

The protein portion, without its cofactors

Question 2

Holoenzyme

Answer 2

An enzyme containing all its cofactors

Question 3

Cofactors

Answer 3

Metal ions - inorganic

Coenzymes - organic

Question 4

Prosthetic group

Answer 4

A cofactor which is covalently bound to the enzyme

Question 5

Active site micro-environment contribution to catalysis:

Answer 5

Exclude excess water

Provide optimal orientation

Binding interactions between the substrate and the enzyme to create a transition state

Presence of catalytic functional groups

Question 6

Michaelis-Menten assumptions

Answer 6

The concentration of ES is relatively constant after the initial reaction time.

The reaction must be considered early, before any appreciable amount of product has been generated.

The product release is a rapid step in the process.

Question 7

Velocity of a rxn in relation to the rate constant

Answer 7

v = k[S]

Question 8

What AA’s are phosphorylated by kinases?

Answer 8

Serine, Threonine, and Tyrosine

Question 9

For competitive inhibitors

Answer 9

vmax remains the same, but Km increases

Question 10

For uncompetitive inhibitors

Answer 10

vmax and Km decrease

Question 11

For mixed inhibitors

Answer 11

decrease vmax, but can increase or decrease Km

Question 12

For noncompetitive inhibitors

Answer 12

decrease vmax, but has no effect on Km

Question 13

How to determine equation for no inhibition

Answer 13

It will have the lowest slope and y-intercept

Question 14

Turn over number

Answer 14

Kcat.. Use this EQ to solve for it

Vmax = Kcat [E]t

Question 15

Catalytic efficiency

Answer 15

aka specificity constant

Kcat/Km

Question 16

High Km

Answer 16

Low affinity

Question 17

Low Km

Answer 17

High affinity

Question 18

two models to explain how the binding of

enzyme and substrate occurs

Answer 18

Lock and Key

Induced Fit

Question 19

Substrate AKA

Answer 19

Reactant

Question 20

Lock and Key Model

Answer 20

Substrate fits perfectly with the enzyme

Question 21

Induced Fit Model

Answer 21

Enzyme is flexible to accommodate the ill fitting
substrate

Permits a much larger number of weaker
interactions between the substrate and enzyme

Question 22

EX of an induced fit mechanism

Answer 22

Hexokinase

Question 23

Critical Aspects of Enzyme Structure and Function

Answer 23

Enzymes bind to substrates with high affinity and
specificity

Substrate binding to the active site induces
changes in the enzyme

Enzyme activity is highly regulated in cells

Question 24

Active sites AKA

Answer 24

Binding pockets

Question 25

Modes of enzyme regulation

Answer 25

Bioavailability: Amount of enzyme present in the cell Catalytic efficiency: Quantitative measure of enzyme activity

Question 26

Organic catalysts vs enzymes

Answer 26

catalysts speed up reactions but not as fast as enzymes Enzymes are highly specific where as catalysts are not

Question 27

Enzymes alter the rates of reaction without changing | the ratio of:

Answer 27

substrates and products at equilibrium

Question 28

6 Major groups of enzymes:

Answer 28

``` Oxidoreducatase Transferase Hydrolase Lyase Isomerase Ligase ```

Question 29

Oxidoreducatase

Answer 29

Oxidation/reduction, Transfer of H or O atoms

Question 30

Transferase

Answer 30

Transfer of functional group

Question 31

Hydrolase

Answer 31

Formation of two products by hydrolyzing the substrate

Question 32

Lyase

Answer 32

Cleavage of C-C, C-O and C-N and other bonds by means other than hydrolysis or oxidation

Question 33

Isomerase

Answer 33

Intramolecular rearrangements, transfer of groups with in a molecule

Question 34

Ligase

Answer 34

Formation on C-C, C-O, C-S and C-N bonds using ATP cleavage

Question 35

3 ways enzymes increase the rate of a reaction:

Answer 35

They lower the activation energy by stabilizing the transition state They provide an alternate path for product formation They reduce entropy by orienting the substrates appropriately for the reaction to occur

Question 36

Physical and Chemical Properties of Active Sites

Answer 36

Hydrophobic regions and charged regions

Question 37

Enzymes decrease the ____ of the reaction

Answer 37

Δ𝐺‡

Question 38

Michaelis-Menten constant

Answer 38

Km = (k-1 + k2) / k1 Describes rates of breakdown and formation of ES

Question 39

Catalytic efficiency of an enzyme is regulated by:

Answer 39

reversible and irreversible inhibition, allosteric control, covalent modification, and proteolytic processing

Question 40

Reversible inhibition

Answer 40

Noncovalent bonding Includes: Competitive, uncompetitive and mixed Can be decreased by diluting the enzyme reaction

Question 41

Irreversible inhibition

Answer 41

forms a covalent bond or very strong non-covalent bond "suicide inhibitors" kill the enzyme Not affected by enzyme dilution

Question 42

Diisopropylfluorophosphate an example of:

Answer 42

Irreversible Inhibitor Blocks protease and phospholipase enzymes

Question 43

A Reversible Inhibitor ex

Answer 43

Malonate Competes with succinate to bind to the active site of succinate dehydrogenase

Question 44

Type of inhibition that can be overcome by increasing [S]

Answer 44

Competitive

Question 45

Competitive inhibition:

Answer 45

E + S --> E S --> E +P II EI

Question 46

Uncompetitive inhibition:

Answer 46

E + S --> E S --> E +P .................II .................ESI

Question 47

Mixed inhibition: How do you know is it is noncompetitive or not?

Answer 47

E + S --> E S --> E +P II..............II EI.............ESI Ki = Ki' ``` Ki = K-i / Ki Ki' = K-i' = Ki' ```

Question 48

EX of competitive inhibition:

Answer 48

Saquinavir An HIV protease inhibitor Mimics the natural Phe-Pro dipeptide substrate

Question 49

Fxn of Saquinavir

Answer 49

HIV protease essential for processing of proteins in virus. | Without these proteins, viable viruses can not be released to cause further infection

Question 50

Uncompetitive inhibitors bind to the:

Answer 50

enzyme-substrate complex and alters the active site conformation

Question 51

Mixed inhibitors bind to sites unique from the _____

Answer 51

active site

Question 52

Kcat =

Answer 52

K2

Question 53

How do enzymes fxn so efficiently?

Answer 53

When S binds to active site on E they make and ES complex, While in the transition state, binding occurs which allows S to interacting with different AA's in the active site, during these small weak interactions, energy is released, and it accumulates to make "binding energy" which is used to lower Ea

Question 54

K(t)

Answer 54

Ae^(-Ea/Rt) | If Ea goes down, K(t) goes up which means Rate goes up!

Question 55

Ea is the same as

Answer 55

Δ𝐺‡