L3- Enzymes

Question 1

enzymes are

Answer 1

biological catalysts that increase the rate of reaction by lowering the activation energy - reduces amount of energy for transition state

Question 2

activations tate

Answer 2

minimum energy substrate must have to allow reaction

Question 3

transition sttae

Answer 3

high energy intermediate that lies between substrate and product

Question 4

what can affect the rate fo reaction

Answer 4

1) temperature 2) concentration 3) enzymes

Question 5

temp

Answer 5

increases number of molecules with activation energy

Question 6

conc

Answer 6

increases chance of molecular collisions

Question 7

enzymes are

Answer 7

highly specific- only work on one substrate

Question 8

enzymes do not affect

Answer 8

reaction equilibrium- will not make an unfavourable reaction favourable

Question 9

enzymes remain

Answer 9

unchanged after the reaction

Question 10

enzymes may require

Answer 10

cofactors

Question 11

active sites at the place where

Answer 11

substrate bind and where chemical reactions occur

Question 12

where are active sites found

Answer 12

occupy small parts of the enzyme - like crevices (exclude water which disrupts reactions)

Question 13

most enzymes are less than ……. amino acids

Answer 13

1000

Question 14

active site have how many amino acids

Answer 14

fews

Question 15

enzymes act as a scaffold to

Answer 15

create the active site (make sure it has the right shape)

Question 16

active site formed by

Answer 16

amino acids from different parts of the primary sequences e.g. alpha helixes and beta sheets

Question 17

two theories of substrate enzyme binding

Answer 17

1) lock and key 2) induced fit

Question 18

lock and key

Answer 18

substrate has a complementary shape to active site

Question 19

induced fit

Answer 19

substrate can induce changes in the conformation- only form complementary shape after substrate binding

Question 20

how are substrate bound to enzymes

Answer 20

multiple weak bonds NON-COVALENT - van der waals -electrostatic - hydrostatic

Question 21

Covalent bonds are usually

Answer 21

permanent

Question 22

enzymes hold substrate in the right

Answer 22

configuration for the reaction to occur

Question 23

enzyme kinetics

Answer 23

• to start the concentration of substrate is high - when the enzyme is added conversion of the substrate to product begins - overtime the tibial rate of reaction V0 will decrease due to the concentration of the substrate being reduced and the enzyme having less substrate to convert to product (why graph plateaus

Question 24

V0

Answer 24

initial rate of reaction

Question 25

diff enzyme have different optimum

Answer 25

pHs and temperatures

Question 26

graph which shows how as concentration increases velocity.

• what shape will it be

Answer 26

Michaelis menton graph

Regtangular hyperbola due to a maximal velocity being reached

Question 27

Vmax

Answer 27

maximal rate at which all enzyme active sites are saturated with substrate

Question 28

Km

Answer 28

substrate concentration that gives half maximal velocity

Question 29

significance of Km

Answer 29

Km values give a measure of the affinity of an enzyme for tis susbtrate

Question 30

a low Km

Answer 30

high affinity for susbtrate

Question 31

a high Km

Answer 31

low affinity for susbtrate

Question 32

hexokinase has a

Answer 32

very low Km - high affinity for glucose (always active compared to glucokinase which only comes active when glucose levels peak after feeding)

Question 33

glucokinase has a

Answer 33

high Km - low affinity for its substrate

Question 34

rate of enzyme catalysed reaction is

Answer 34

proportional to the conc of enzyme e.g. double the amount of enzyme, double the rare

Question 35

Michaelis menton equations

Answer 35

Question 36

lineweaver burk plot

Answer 36

M-M equation can be rearranged to give a linear plot

• allows for easy estimation of Km and Vmax from linear plot

Question 37

Enzyme inhibitors

Answer 37

slow down or prevent an enxyme reaction

Question 38

enzymes inhibitors can bind both ….

Answer 38

reversibly and irreversibly

and

non competitively and competitively

Question 39

irreversible enzyme inhibitors

Answer 39

Bind very tightly

i.Covalent bonds form

E.g. nerve gases such as sarin

Question 40

reversible enzyme inhibitors

Answer 40

Non-covalent

Freely dissociate

• Competitive-binds active site
• Non-competitive-binds to another site on the enzyme

Question 41

non competitive inhibtors bind to

Answer 41

alternative sites and decrease the turnover number of the enzyme

• lowers Vmax
• Km = unaffected

The graph:

• Vmax- where the lines cross the Y axis is differe
• Km: where the line touches the X axis stays the same

Question 42

competitive inhibitors

Answer 42

resembles rthe substrate and bidns tot he active site, reduucing the proportion of enzyme meolcuels bound to the enzyme

E.g. Tamiflu used to treat influenza virus, has a very similar structure to neuraminidase- prevents binding

• no affect on Vmax (adding enough susbtrate will always overcome effect fo the inhibitor)
• Km will increase- inhibitors competes witht he substrate for AS

Lines are at different points on the X axis but both cross the Y axis at the same point

Question 44

drugs can itneract with enzymes to

Answer 44

inhibit the action of enzymes

Question 45

michaelis menton equation shows that

Answer 45

rate of an enzymes catalysed reaction is related to the conc of substrate