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Principles Biochemistry > Lecture 7 Enzyme kinetics > Flashcards

Lecture 7 Enzyme kinetics Flashcards

1
Q

How does increasing substrate impace reaction velocity

A

Increasing substrate soncentration will increase reaction rate until Vmax is reached

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2
Q

What is Vmax

A
  • It is the maximum velocity at which an enzymes catalyses a reaction
  • Once reaction reaches Vmax further increase in substrate concentration does not affect rate of reaction
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3
Q

What happens at Vmax

A
  • The enzyme becomes fully saturated
  • Maximum rate of product production
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4
Q

What is the equation for enzyme reactions

A
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5
Q

What kind of Curve do we get if we plot initail velocity over substrate concentration

A

Hyperbolic curve

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6
Q

What is Km

A

KM is 50% of Vmax

  • The Concentration of subtrate which allows the enzyme to reach half of Its maximum velocity
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7
Q

What is K1

A

The Forward rate constant for enzyme association with substrate

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8
Q

What is K-1

A

Backwards rate constant for enzyme dissociation from subbstrate

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9
Q

What is K2

A

Froward rate constant for enzyme conversion of substrate to product

  • This step is Irreversible
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10
Q

Why does this reaction not go S + E —> P

A

Because the Activation energy barrier (now low) makes the enzyme substrate complex unstable so it can do forwards or backwards

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11
Q

What is the Equation for Michaelis constant KM

A
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12
Q

How is KM and Vmax measured?

A

Measuring the intial reaction velocity V0 at a known substrate concentration and then repeating at increased substrate concentration

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13
Q

What is the Machaelis menten equation

A
  • Describes Rate of catalysis at a function of substrate concentration
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14
Q

What can the Mechaelis menten equation be turned into

A
  • A straight line equation Y= mx+c
  • Used to accuratley determined Vmas and Km
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15
Q

What is the lineweaver Burk Plot

A
  • A double reciprocal plot of the hyperbolic curve
  • 1/V = Km/vMax . 1/[S] + 1/vmax
  • X axis = 1/-KM
  • Y axis = 1/vmax
  • Gradient = KM/vmax
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16
Q

What does a Low kM indicate

A
  • That enzyme needs ony a little substrate to work at its Half maximum velocity
  • More effecient
17
Q

What does a High KM indicate

A
  • Enzyme needs alot of substrate to work at half-maximum velocity
  • Less effecient
18
Q

Clinical Examples of why Km matters

19
Q

What is Reversible Inhibiton

A

Orthosteric inhibition

Allosteric inhibtion

20
Q

What is Reversible competative inhibition

A

inhibitor binds to the active site of enzymes and blocks substrate acess

  • Orthosteric inhibition
21
Q

What is reversible non-competative inhibition

A

Inhibitor binding to a site other than a catalytic centre

inhibits enzymes by chaning its conformation

  • Allosteric inhibition
22
Q

What is Irreversible non-competative inhibition

A

Usually involves formation or breakage of covalent bonds in the enzyme complex

  • Cannot be reversed
23
Q

What does the linweaver Burk plot look like with a competative inhibitor

A
  • Km Varies - (x-axis changes)
  • Vmax does not change (Y-intercept is the same)
24
Q

give an example of Competative inhibition in Clinic

A

Methanol poisoning

  • Enzyme Alcohol dehydrogenase has a Km 20% greater for Ethanol compared to methanol
  • Give patients 40% ethanol - which will increase the enzymes Km for its substrate - means more methanol will be required for enzyme to break it down and form harmful products
25
Q

What does the lineweaver burk plot look like with a non-competative inhibitor

A
  • Vmax varies (y-intercept changes)
  • Km remains the same (x-intercept in same)
26
Q

How do enzymes carried out Feed-back inhibition

A
  • Carried out by Allosteric regulation
  • Methabolic pathways include many enzmyes being formed and making a final product
  • This product can then bind to the allosteric site of an enzyme in the begining of a pathway
  • Which prevents the chain reaction from continueing
  • Simillary if the final product is in low levels then enzymes can continue to make products again
27
Q

Summary

28
Q

Do Allosteric enzymes follow mechaelis menten kenetics

29
Q

How does the curve of an Allosteric enzyme differ from normal enzymes

A
  • Allosteric enzyme = Sigmoid curve

Shows co-operative behaviour

  • Normal enzyme = hyperbolic curve
30
Q

How do allosteric activators and inhibitors effect binding of enzymes

31
Q

Give an example of allosteric regulation

A

Oxygen binding to Haemoglobin

Positive co-operativity

32
Q

what factors cause the curve of oxygen-haemoglobin binding to change

A
  • H+ ions
  • CO2
  • 2,3 Bisphosphoglycerate - side product of glycolysis
33
Q

Questions to revise

Principles Biochemistry (7 decks)

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