Enzymes

Question 1

2 sites on the active site

Answer 1

binding site
catalytic site - reduce chemical activation energy

Question 2

forces involved in binding

Answer 2

h bonds, hydrophobic interactions, van Der Waals, electrostatic, reversible covalent

Question 3

what determines substrate specificity

Answer 3

side chains

Question 4

allosteric sites

Answer 4

different from active site
binding = conformational change = change in rate of reaction
regulation

Question 5

co factors

Answer 5

help enzyme catalyse reaction

Question 6

transferases

Answer 6

transfer functional group from substrate to substrate

Question 7

hydrolases

Answer 7

hydrolysis of substrate

Question 8

lyases

Answer 8

adding or removing group to form double bond

Question 9

isomerases

Answer 9

transfer groups within molecules

Question 10

ligases

Answer 10

bond formation coupled with atp hydrolysis

Question 11

transition state

Answer 11

transient molecular state that is no longer substrate or product

Question 12

2 types of enzyme reaction

Answer 12

exergonic - spontaneous (produced more energy than input
endergonic - unfavourable (require more energy than it yields)

Question 13

factors involved in enzyme catalysis

Answer 13

R groups
chemical complementarity
microenvironment
orientation
hydrophobic interactions
ionic bonds
h bonds
transient covalent
van der Waals

Question 14

4 catalytic mechanisms

Answer 14

metal ion catalysis (involves metal ion cofactor)
catalysis by approximation (bring reactants closer)
covalent catalysis (share e-)
acid-base catalysis (adding either speeds up)

Question 15

rate of reaction is called

Answer 15

velocity (V0) (amount of S covered to P per time)

Question 16

unit for V0

Answer 16

micro mol / min

Question 17

is substrate doubles V0…

Answer 17

doubles

Question 18

if enzyme saturation occurs V0…

Answer 18

plateaus

Question 19

rate of reactions depend o dissociation of …

Answer 19

product from enzyme

Question 20

if enzyme doubles, V0…

Answer 20

doubles

Question 21

Vmax

Answer 21

max rate of reaction

Question 22

Km

Answer 22

substrate conc at half Vmax
(measure of enzyme affinity for substrate)

Question 23

low Km =

Answer 23

high affinity for substrate
strong binding
greater V0
faster rate of reaction.

Question 24

enzyme assays

Answer 24

monitors disappearance of substrate or appearance of product

Question 25

measurements of enzyme assays

Answer 25

colour
high absorbance / fluorescence
chromatography
radiography

Question 26

substrate analogues

Answer 26

chemical compound that is similar in structure to substrate

Question 27

reversible inhibition

Answer 27

bind by weak covalent but don’t change shape chemically

Question 28

competitive inhibitor effect on Vmax, half Vmax and Km

Answer 28

Vmax unchanged
Km increases - rate is reduced and affinity of enzyme reduces
half Vmax unchanged

Question 29

non competitive inhibitor effect on Vmax, half Vmax and Km

Answer 29

Vmax reduced
Km unchanged
half Vmax reduced

Question 30

uncompetitive inhibition

Answer 30

binds only to enzyme substrate complex
all 3 reduce

Question 31

regulation of glycolysis (hexokinase)

Answer 31

allosterically inhibited by G-6-P

Question 32

allosteric enzymes features

Answer 32

multi subunit (active site on each subunit = oligomeric)
cooperatively (binding = conformational change = increase affinity)
regulated via allosteric sites

Question 33

allosteric enzyme graph

Answer 33

sigmoidal curve (rapid increase in enzyme velocity)
narrow range of s
sensitive to small changes in s

Question 34

reversible covalent modification

Answer 34

adding or taking Pi changes tertiary structure and alters catalytic activity eg
protein kinases - phosphorylates
protein phosphatases - dephosphorylates

Question 35

proteolytic activation

Answer 35

when hydrolysed they are active (irreversible hydrolysis of one or more peptide bond)

Question 36

other methods of regulation

Answer 36

gene expression
breakdown as short half life