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Science For Medicine > enzymes > Flashcards

enzymes Flashcards

1
Q

what is an enzyme

A

globular protein

can be regulated reaction specificity

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2
Q

what are ribozymes

A

have no protein but are catalytic RNA molecules

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3
Q

what is a cofactor

usually what is it

A

non protein component needed for activity

CHANGES PROTEIN SHAPE

an ion of some sort

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4
Q

what is a co enzyme

what are some examples

A

produced by vitamin take part in reaction
but don’t alter the shape of a enzyme

FAD, NAD+

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5
Q

what is a prosthetic group

A

a co factor that doesn’t alter group but is attached closely and is needed to function

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6
Q

all enzymes end in

A

-ase

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7
Q

what do enzymes do

A

acceleration towards reaction equilibrium

lower the activation energy

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8
Q

what is the best shape for an active site

A

the shape is complementary to the transition complex

lock and key is a load of bollocks

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9
Q

how do enzymes reduce activation energy

A

desolvation - single out substrate from solution
induced fit
entropy reduction

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10
Q

what happens if you add more substrate

A

a higher initial reaction rate and more product

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11
Q

what is the initially reaction velocity called

A

V0

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12
Q

when do you reach Vmax

A

when you have saturated all enzymes with substrate

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13
Q

do you ever reach Vmax

A

not really

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14
Q

what dose a larger Km indicate

A

a less stable enzyme substrate complex

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15
Q

what dose a smaller Km value indicate

A

a more stable enzyme substrate complex

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16
Q

what is Km

A

the substrate concentration to reach 1/2 Vmax

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17
Q

so what dose
Vmax tell us
Km tell us

A

Vmax - fast - higher the better

Km - fit - the higher the number the less the affinity - faster

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18
Q

what the two Isozymes that catalyse glucose + ATP = glucose-6-phospahte

A

glucokinase

hexokinase

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19
Q

where is glucokinase located

A

in the liver

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20
Q

where is the hexokinase located

A

everywhere else in the body

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21
Q

what are the properties of glucokinase

A

high Km

high Vmax

22
Q

what are the properties of hexokinase

A

low Km

low Vmax

23
Q

what happens after you eat a meal and blood glucose goes up

A

hexokinase activity doesn’t respond however glucokinase responds PORPORTIONATLLY to blood glucose

24
Q

what happens when blood glucose is low

A

gluconeogenis realsease glucose from liver

but glucokinase cant phosphorolate the glucose due to its high Km

25
Q

what happens when glucose is phosphorylated

A

it is unable to cross a cell membrane

26
Q

when enzymes are in the blood tissue this is an indicator of

A

tissue damage

27
Q

how can you separate out proteins

A

electrophoresis

28
Q

what can electrophoresis separate proteins out by

A

charge or size

29
Q

the measurement of enzyme concentration or presence can help with making a…

A

diagnosis

30
Q

hexokinase has different Km values for which two sugars

why the difference

A

glucose - low
fructose - high

main job is to phosphorylate glucose but can phosphorylate fructose if need be

31
Q

the catalysing of a reaction with two or more substrates usually involves…

A

the transfer of one group to another

32
Q

what dose lactate dehydrogenase exhibit

A

ordered sequential mechanisms

33
Q

what is ordered sequential mechanisms

A 
into enzyme 
A 
then B 
then A out 
then B out
34
Q

what is a random sequential mechanism

A

enzyme binds A or B first
then spits out A or B first

RANDOM

35
Q

what are double displacement/ ping pong reactions

A

to create A + B = C + D

A in = C out
B in = D out

36
Q

what is an example of double displacement

A

transfer of amino acid from aspartate to alpha-ketoglutarate

37
Q

what are allosteric enzymes

A

enzymes which have other sites on them that can be regulated

38
Q

what is a good example of cooperative binding

A

haemoglobin

39
Q

what is cooperative binding

A

when the reaction velocity V0 increases after a substrate binds to one subunit - leading to increased affinity of the other sub units

40
Q

what is a competitive inhibitor

A

bind noncovalently to active site and have simillar shape to substrate

will increase the Km and reduce the affinity

41
Q

what is a uncompetitive inhibitor

A

stops conformational change once enzyme and substrate have bound

42
Q

what is a non-competitive inhibitor

A

binds to a different ‘allosteric site’ causing a change in active shape

43
Q

what is the best shape for an inhibitor

A

something that looks like the transition state

44
Q

what is the concert model

A

when one molecule of substrate binds - it locks the other enzymes open

45
Q

what do allosteric actiuvators do

A

stabilise the ‘open’ conformation allowing S to bind more effectively

46
Q

what will allosteric inhibitors do

A

will stabilise the ‘closed’ conformation and make it difficult for S to bind

47
Q

what is the sequential model

A

after one substarte bids it opens its next door neighbour are that continues in SEQUENCE

48
Q

what is a proenzyme

A

Enzymes that exist as an inactive precursor protein

49
Q

how are the active enzymes formed from proproteins

A

the proprotein is cleaved by protease

50
Q

what is covalent modification

A

regulation by the covalent binding of a phosphorylation group

51
Q

what do Protein kinases do

A

add a phosphoryl group

52
Q

what do Protein phosphatases do

A

remove phosphoryl groups

Science For Medicine (17 decks)

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