Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Principles: Biochemistry > Enzyme Kinetics > Flashcards

Enzyme Kinetics Flashcards

1
Q

how do enzymes have implications in disease

A

small changes in their abundance, efficiency or distribution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why can enzymes be used in lab to diagnose and develop therapeutic drugs

A

enzymes control well defined chemical reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

role of enzyme

A

catalysts
convert specific substrateto product
more substrate = more chance of enzyme working on it = more product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is saturation

A

increasing substrate conc is no longer the limiting factor as all active sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is Vmax

A

max rate at which enzymes can convert substrate to product per sec

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is Km

A

50% of max rate enzymes convert substrates to product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what model is used to explain the relationship between km and Vmax

A

Michealis-Menten
[ES] = K1[E][S]/(K-1+K2) constants on one side of the reaction
combination of rate constants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the activation barrier

A

point in reaction where energy is at its highest, enzyme substrate complex is leas stable and if barrier isn’t overcome, enzyme-substrate complex can go backwards

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the rate constants in and enzyme substrate reaction

A

K1, K-1, K2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how are Vmax and Km measured

A

measure initial velocity Vo at a known substrate conc

Repeat at increasing substrate conc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the Michaelis constant Km equivalent to

A

substrate concentration where initial reaction is half maximal
reaction velocity never quite reaches true Vmax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what does the michaelis-menten equation describe

A

rate of catalysis as a function of substrate concentration

Velocity = max velocity/50% velocity + substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is used to determine Vmax and Km

A

Michaelis-equation
can be written as
1/v = Km/Vmax x 1/s + 1/vmax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the line weaver-burk plot

A

accurate determination of Vmax and Km

we plot 1/v against 1/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is Vmax on line weaver-burk plot

A

intersection of straight line with Y axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is Km on line weaver-burk plot

A

intersection with x axis

-1/Km

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the conc of substrate at the x intercept

A

infinity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is Vmax

A

maximum velocity of reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is Km

A

conc in moles of substrate which gives 1/2 Vmax

Km = [S] at 0.5 Vmax

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when substrate concentration becomes smaller what do enzymes with steeper graphs do

A

work better at lower substrate concentrations as they are good at finding substrate and converting it to product
if slope is gradual enzyme doesn’t work well with low substrate concentration as more sensitive to changes in substrate conc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

role of hexokinase

A

catalyses first reaction in glycolysis

works fast even when substrate conc is low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does it mean if an enzyme has a high Km

A

sensitive to changes in substrate concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

does hexokinase in red blood cells have a high or low Km

A

low Km = 0.05mM

Low Km maintains energy production in rbcs by glycolysis even if glucose falls

24
Q

what is normal fasting blood glucose

A

5mM

25
Q

what 2 enzymes catalyse glucose + ATP -> glucose-6-phosphate + ADP

A

Glucokinase - High Kw

Hexokinase - Low Kw

26
Q

why does glucoskinase have a high Kw

A

enables glucose sensing, homeostasis
abundant in liver is regulated by insulin
excess blood glucose is metabolised
loss of activity - type 1 diabetes

27
Q

oxygen sensors and what they are regulated by

A

propel hydroxylases

regulated by transcription factor HIF (hypoxia inducible factor)

28
Q

what happens when prolyl hydroxylases are activated

A

genes for surviving hypoxia stitched on
rbc synthesis
blood vessel growth
anaerobic survival pathway

29
Q

substrate of proline hydroxylases

A

oxygen to regulated HIF transcription factor

30
Q

proline hydroxylase have a high Km for oxygen what does this mean

A

they aren’t good at finding substrate

therefore work as good receptors

31
Q

2 types of reversible inhibition

A

competitive - inhibitor binds to active (catalytic) site and blocks substrate access - orthosteric inhibition (at same time)
Non competitive - inhibitor binds to allosteric site (not the catalytic centre) and inhibits enzyme by changing its conformation

32
Q

example of irreversible inhibition

A

non-competitive

involved formation or breakage of covalent bond in enzyme complex

33
Q

does competitive inhibition change Vmax or Km

A 
Vmax does not change (y intercept) 
Km varies (x intercept)
34
Q

give example competitive inhibition in the clinic

A

methanol poisoning
methanol is substrate for alcohol dehydrogenase (ADH), causes tissue damage/blindness by conversion to formaldehyde and drives metabolic acidosis
ADK Km for ethanol 20x greater so patient treated with ethanol

35
Q

does non-competitive inhibition affect Vmax or Km

A 
Km is the same (x intercept, -1/Km)
Vmax varies (y intercept, 1/Vmax)
Vmax is lower enzyme finds it more difficult to find substrate
36
Q

what is feedback inhibition

A

inhibition of rate limiting enzymes by end product - allosteric control
end product is an inhibitor to an enzyme earlier in the pathway
avoids build up of intermediates in pathway

37
Q

what type of curve do allosteric enzymes have

A 
Sigmoidal curve (not hyperbola)
they do NOT follow Michaelis-Menten kinetics
38
Q

what are allosteric enzymes controlled by

A 
allosteric inhibitor (curve lower)
allosteric activator (strap higher and steeper)
39
Q

in allosteric enzymes are Km and Vmax affected

A

Yes

40
Q

example of allosteric regulation

A

binding of oxygen to haemoglobin
positive cooperatively
controlled by - H+, CO2, 2,3 bisphosphoglycerate (glycolysis side product)

41
Q

my does myoglobin not show co-operativity

A

haemoglobin more sensitive to changes in concentration than myoglobin

42
Q

what is Vo

A

initial reaction velocity at known substrate conc

43
Q

what is K1

A

reaction form enzyme to enzyme substrate complex

44
Q

what is K2

A

reaction from enzyme-substrate complex to product

45
Q

what is K-1

A

back reaction from enzyme substrate complex back to enzyme

46
Q

why can Vmax and Km not be measured accurately from hyperbolic plot of V/S (why double reciprocal is used)

A

the kinetics are not linear so reaction velocity never quite reaches true Vmax

47
Q

in line weaver-burk complex enzymes with high Km will tend towards zero intercept on X axis

A

True

48
Q

what is the Michaelis-Menten Equation

A

Vo = Vmax [S]/Km [S]

49
Q

line weaver-burk straight line equation

A

1/Vo = Km/Vmax x 1/[s] + 1/Vmax

50
Q

how do competitive inhibitors work

A 
Form EI (enzyme inhibitor complex) + substrate which cannot react
K1 step
51
Q

how doe uncompetitive inhibitors work

A 
forms ESI (enzyme substrate inhibitor) w
cannot react
52
Q

what is a non-competitive inhibitor

A

mixed
can bind to E forming EI
or ES forming ESI

53
Q

what happens to line weaver burke slope as you increase competitive inhibitor

A

slope gets steeper as inhibitor increases
so if no inhibitor present slope more gradual
y intercept doesn’t change
increase in Km
Vmax unchanged

54
Q

what happens to line weaver burke slope as you increase uncompetitive inhibitor

A

all 3 lins have same slope but different yintercepts
increase in inhibitor = decrease in Vmax
enzyme works at low substrate concentrations

55
Q

effect of increasing non-competitive inhibitor on line weave burke slope

A

increases in slope
increase in Km
decreased Vmax

56
Q

a plot of V[s] will always produce a hyperbolic relationship

A

false not true for allosteric enzymes

Principles: Biochemistry (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions