Enzymes

Question 1

Enzymes role

Answer 1

Increase rate of chemical reactions
Doesn’t change free energy of products or reactants
Decrease activation energy

Question 2

Basis of catalysis

Answer 2

Reactions through high-energy transition states

Question 3

Oxidoreductases

Answer 3

Redox

Question 4

Transferases

Answer 4

Transfer of functional groups

Question 5

Hydrolases

Answer 5

Hydrolysis reactions

Question 6

Lyases

Answer 6

Non-hydrolytic breaking/making bonds

Question 7

Isomerases

Answer 7

Transfer within molecule yield isomeric form

Question 8

Ligases

Answer 8

Join 2 molecules

Question 9

Active site

Answer 9

Bind substrate via a.a side chains via weak interactions

Determines specificity of reaction

Question 10

Types of bonds

Answer 10

Ionic
Hydrogen
Van der Waals interactions
Covalent

Question 11

Models for enzyme fits

Answer 11

Lock and key
Induced fit
Complementary to substrate

Question 12

Enzymes fit bonds

Answer 12

Many weak interactions

Specificity and reversibility

Question 13

Types of catalysis

Answer 13

Acid-base
Covalent
Redox & radical
Geometric effects
Stabilisation through transition state 
Co factors

Question 14

Types of co-factors

Answer 14

Metal ions - orientates substrates
Co enzymes (from vitamins)

Question 15

Evolutionary history

Answer 15

Same structure, unique specificties

Question 16

Convergent evolution

Answer 16

Same catalytic triad - different order & structure

Question 17

Chymotrypsin

Answer 17

Acid - base and covalent cataysis

Cleaves protein at hydrophobic residue = easy to be absorbed in digestion

Question 18

Oxyanion hole lowers..

Answer 18

activation energy

Question 19

Model for Michaelis-Menten equation

Answer 19

E+S <=> ES -> E+P

Question 20

K1 & K-1 =

Answer 20

How tightly substrate binds

Question 21

K2 =

Answer 21

Rate of cataylsis, energy of activation

Question 22

[ES] =

Answer 22

Controls rate

Question 23

Progress curve

Answer 23

Appearance of products over time
Vo
Tangant to beginning of reaction

Question 24

Vo proportional [E] when

Answer 24

substrate excess

Question 25

Vmax =

Answer 25

max velocity when [S] infinite

Question 26

Km =

Answer 26

Vmax/2

Question 27

Michaelis-Menten equation

Answer 27

Vobs = Vmax[S]/ | Km + [S]

Question 28

Michaelis-Menten assumptions

Answer 28

Product not convented to substrate Rate of [ES] formation and breakdown equal Inital rate = [S] doesn't change significantly

Question 29

First order kinetics

Answer 29

ES -> E + P

Question 30

Lineweaver-Burk Plot x and y axis

Answer 30

``` x = 1/[S] y = 1/Vo ```

Question 31

Lineweaver-Burk Plot x and y intercept

Answer 31

``` x = -1/Km y = 1/Vmax ```

Question 32

Km high/low =

Answer 32

low/high affinity (opposite)

Question 33

Kcat

Answer 33

No of substrate converted to product, per enzyme, per unit of time Catalytic activity

Question 34

Catalytic efficiency

Answer 34

kcat/km = higher the better | Limit - diffusion controlled rate (10^8s-1m-1)

Question 35

Inhibitors function

Answer 35

bind to enzyme and reduce activity

Question 36

Irreversible inhibitor

Answer 36

Binds covalently | Permantly inactivates

Question 37

Reversible inhibitor

Answer 37

Bind noncovantly Can be released Competitive and noncompetitive

Question 38

Competitive reversible inhibitor

Answer 38

``` Compete with substrate in active site Vmax same Km increase [S] increase = outcompete inhibitor Slower rate ```

Question 39

Noncompetitive reversible inhibitor

Answer 39

Binds to different site to active site Pure Mixed

Question 40

Pure noncompetitive reversible inhibitor

Answer 40

Vmax decrease | Km same

Question 41

Mixed noncompetitive reversible inhibitor

Answer 41

Vmax decrease | Km increase

Question 42

Enzymes and treatment eg 2 types of alcohol

Answer 42

Toxins produced during metabolism of some alcohols | Alcohol with lower km = likely to be metabolised e ethanol

Question 43

Receptors types

Answer 43

Across membrane Transmit signal across membrane Membrance bound enzymes Intracellular

Question 44

Enzyme features

Answer 44

1 active site BInds and changes substrates into products Membrane bound/free in cytosol

Question 45

Receptor features

Answer 45

Several binding site Bind and release ligans unchanges Membrane bound/free in cytosol

Question 46

Receptor definition

Answer 46

Protein molecules that receives chemical signals outside cells

Question 47

Ligand definition

Answer 47

Molecule/drug that binds to receptor

Question 48

Agonist

Answer 48

Chemical capable of activating receptor to indue response

Question 49

Antagonist

Answer 49

Blocks receptor and stops effects

Question 50

Alcohol _____ at _____ receptor

Answer 50

agonist at GABAa

Question 51

GABAa receptor

Answer 51

Membrane bound ligand gated Cl- channel | Iinhibitory

Question 52

GABAa receptor + alcohol

Answer 52

Open channel, allows Cl- into cell | Decrease activity in nervous system

Question 53

Consequences of alcohol

Answer 53

Varies on dose and person | Person = different expression of receptor = different response

Question 54

Useful features to build drug

Answer 54

Catalyse reactions Active site Preferred substrates Can be inhibited (competitive)

Question 55

Design inhibitor

Answer 55

Know active site and substrate

Question 56

HIV Protease inhibitor active site

Answer 56

Cleaves a.a. with common structure with hydrophobic rings (bulky) + Asp residues = position substrate

Question 57

HIV Protease inhibitor substrate

Answer 57

Cleave peptide bond from long a.a chain

Question 58

Making drug

Answer 58

1) build peptide-like backbone 2) add bulky side groups to fit active site 3) rest of drug = soluble

Question 59

Testing

Answer 59

Competitive = Vmax same, Km increase