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FMS > [FMS] CBS - enzymes > Flashcards

[FMS] CBS - enzymes Flashcards

1
Q

are enzymes stabilised by weak or strong bonds?

A

weak bonds

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2
Q

which one of these is NOT weak bond involved in enzymes

H-bonds,
electrostatic salt bridges
Van der Waals
ionic bonds
hydrophobic interactions.

A

ionic bonds

strong bonds = HHEV

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3
Q

who made the lock and key theory and what is it?

A

Emil Fisher 1884 - enzymes are complementary to their substrate explaining high specificity but misleading

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4
Q

who made the induced fit theory and what is it?

A

Induced Fit: Daniel Koshland 1958 - enzymes undergo conformational change upon substrate binding induced by weak interactions with substrate

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4
Q

what is enzyme specificity determined by?

A

Determined by cleft or groove of defined shape - the ‘active site’ into which only the substrate of correct shape and charge can fit

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5
Q

What is a transition state? if you stabilise the transition state what happens to the enzyme?

A

An unstable, high-energy intermediate in a chemical reaction:
stabilising the transition state is one way that enzymes can speed
up a reaction

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6
Q

the enzyme must be complimentary to what?

A

the transition state

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7
Q

how many enzyme classes are there? what are they called?

A

6:

oxidoreductases
transferases
hydrolases
lyases
isomerases
ligases

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8
Q

what does an oxidoreductase do? give an example?

A
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9
Q

what does a transferase do? give an example.

A
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10
Q

what does a hydrolase do? give an example.

A
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11
Q

what does a lyase do? give an example.

A
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12
Q

what does a isomerase do? give an example.

A
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13
Q

what does a ligase do? give an example.

A
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14
Q

how are enzymes classified?

A

by a 4 digit number

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15
Q

effect of temp on enzymes

A

Weak bonds stabilising structures are easily broken by heating protein giving rise to disorganised/tangled structure in which enzyme has no catalytic activity (denatured/inactive).

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16
Q

DIRECT effect of ph on enzyme-controlled reactions?

A

[H+] or [OH-] appear in rate equation

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17
Q

2 SUBSTRATE effects of ph on enzyme-controlled reactions?

A
  • changes in ionisation state of substrate = additional acid/base catalysis
  • changes leading to altered binding to enzyme =change in Km
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18
Q

2 effects of ph ON ENZYME controlled reactions?

A
  • unfolding of the enzyme leading to complete inactivation
  • changes in ionisation state of active site residues leading to change in Km (substrate binding) or Vmax (involved in reaction).
19
Q

what is enzyme kinetics

A

The study of the rate of an enzyme catalysed reaction

20
Q

what is the Michaelis Menten equation

A
21
Q

whats the shape of Michaelis menten equation on a graph

A

hyperbolic curve

22
Q

V0

A

initial reaction velocity, measured as soon
as enzyme and substrate are mixed.

23
Q

what is Vmax and where is it found

A

maximal velocity of an enzyme
catalysed reaction i.e. when all the enzyme
active sites are fully saturated with substrate

found on top of graph.

24
Q

what is Km, where is it found on graph

A

Michaelis constant
Km= (k-1 + k2)/k1

Therefore Km is the substrate concentration at half maximum velocity of the reaction

found on x axis at bottom of graph

25
Q

what is [S]

A

= substrate concentration

26
Q

when V0 = 0.5Vmax …

A

Km = [s]

27
Q

what is Kcat

A

number of substrate molecules converted to product in a unit of time on a single enzyme molecule when the enzyme is saturated with substrate.

28
Q

3 assumptions of Michaelis Menten

A

3 assumptions:

  1. [S] > [E] so amount of substrate bound by enzyme at any one time is small
  2. Initial velocities used, concentration of product small so back reaction (k2) is small = ignored
  3. [ES] does not change with time (steady-state) - formation ES = breakdown ES:
29
Q

how to compare catalytic efficiency

A

Kcat/Km

30
Q

lineweaver burk plot equation

A
31
Q

on the Lineweaver Burk plot, where is 1/Vmax

A

y axis

32
Q

on the Lineweaver Burk plot, where is -1/Km

A

x axis

33
Q

in enzyme inhibition, what does a competitive inhibitor do to Km and Vmax

A

increase Km
same Vmax

34
Q

in enzyme inhibition, what does a non-competitive inhibitor do to Km and Vmax

A

same Km
decrease Vmax

35
Q

what 2 things do competitive inhibitors do? give an example

A

block the enzyme active site
interfere with catalytic mechanism

36
Q

2 types of irreversible enzyme inhibitors

A

*AChE (Acetylcholinesterase)
inhibitors
* organophosphates
- Insecticides
- Nerve agents NOVICHOK

37
Q

shape of graph for allosteric modulation

A

sigmoidal

38
Q

in allosteric enzyme kinetics, what does a high Km value correspond to?

A

t-state

39
Q

in allosteric enzyme kinetics, what does a low Km value correspond to?

A

R-state

40
Q

when would you have a positive or negative allosteric modulator>

A
41
Q

describe the covalent modification of enzymes

A

reversible addition/removal of phosphate from SER/THR/TYR/HIS residues by kinase/phosphatase enzymes - active or inactive:

42
Q

How do allosteric enzymes regulate enzyme activity

A

end product of the metabolic pathway is an allosteric inhibitor to the beginning of the pathway, controlling the production of the end product

43
Q

do keats quiz on enzymes

A

https://keats.kcl.ac.uk/mod/quiz/view.php?id=7540181

44
Q

What is the relationship between the kinetic properties of an enzyme (Vmax and Km) and the affinity of the enzyme for its
substrate?

A

An enzyme with a low Km has a high affinity for its substrate irrespective of the Vmax of the enzyme

FMS (33 decks)

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