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BIOC192 > Lecute 11 > Flashcards

Lecute 11 Flashcards

1
Q

Enzymes catalyse thermodynamically favourable reactions by…

A

Lowering activation energy

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2
Q

What does a progress curve measure?

A

The appearance of product ( or disappearance of substrate) with time

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3
Q

Spectrophotometetry

A

A way of measuring compounds in solution

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4
Q

Shape of progress curve

A
  • goes from a linear rate creating product from substrate into a curve
  • linear as it just depends on the parameters of the enzyme, - where we do pristine experiments because things aren’t limiting
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5
Q

What is the initial linear part of the curve called?

A

Initial velocity

  • only part that can be used
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6
Q

Velocity of an ezyme refers to

A

Idealised path in a progress curve
- Measured rate of formation of a product

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7
Q

It is important to measure…

A

The initial reaction velocity (rate) i.e at time zero- symbol is Vo or Vi or Vinit

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8
Q

Enzyme conc and reaction rate - EXCESS SUBSTATE - will never get to curve of progress curve

A
  • as the amount of enzymes increased, the rate of reaction increases
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9
Q

When substate is not limiting Vo is proportional to…

A

Enzyme concentration (E)

ONLY WHEN SUBSTRATE IS IN EXCESS

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10
Q

When there is a fixed amount of enzymes as the amount of substate is increased, the rate of reaction:

A

Increases in a linear way at first but as all active sisters become occupied, the rate of reaction stops increasing

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11
Q

First order kinetic rate

A
  • depends on substrate concentration
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12
Q

Second order kinetics

A
  • rate doesn’t depend on substate concentration
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13
Q

V max =

A

Maxiumum velocity possible, with a fixed amount of enzyme and unlimited substrate

  • how fast it will go with everything ideal?
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14
Q

What is Km

A

The substate concentration at which V = Vmax/2

Michaelis constant
- related to how well your enzyme binds to substrate - how well it deals with low amounts of substrate

  • low km = doesn’t need much to get going at half of it maximum velocity - good at achieving half its maximum velocity
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15
Q

What equation describes the V vs [S]

A

Michaelis-menten equation

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16
Q

Michelins menten equartion

A
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17
Q

Many ____ obey the _______________ belabour, this is how we determine their _____ parameters

A

Many enzymes obey Michaelis-menten behaviour, and this is how we determine their kinetic parameters

18
Q

Simplifying assumptions of MM model

A
  • product is not converted back to substrate
  • holdane stready state assumption: rate of ezyme substrate formation = its rate of breakdown
  • by measuring initial rate we assume the substrate conc doesn’t change overtime
19
Q

How to determine Km and Vmax

A
  • V vs [S] curve is hyperbolic thus hard to directly determine Vmax and Vmax values
  • plotting 1/V against 1/[S] gives a straight line

LINEWEAVER-BURK PLOT - intercepts tell us the plots

20
Q

On the lineweaver-burk plot, the Y-int means

A

1/Vmax

21
Q

On the line weaver-burn plot the x-int shows

A

-1/Km

22
Q

What does the slope of the lime weaver-burk plot represent

A

Km/Vmax

23
Q

What does Km characterise

A

Km characterises one enzyme-substrate pair (if an enzyme can act on different substrates, it will have a different Km value for each)

24
Q

Km is the substrate concentration needed to….

A

Reach half Vmax

25
Q

Units of Km

A

Concentration - mol/L

26
Q

Low Km =

A

High affinity between enzyme and substrate

27
Q

High Km =

A

Low affinity for substrate

28
Q

Km is appox..

A

Kd (dissociation constant) - how tightly the enzyme substrates interact

29
Q

km as an indicator of substrate preference

A
30
Q

In the cell, for a particular_________ interaction, __ is often below the _____. This means _____ control is effective.

A

In the cell, for a particular enzyme-substrate interaction, [S] is often below the Km. This means rate control is effective.

31
Q

Physiological substrate concentration

A
  • there is enough enzyme sites available so that substate molecules are not cueing up
32
Q

The turnover number:

A

Kcat

33
Q

What is the Kcat?

A
  • the number of substrate molecules converted to product per enzyme, per unit of time, when Enzyme is saturated with substrate
  • therefore helps to define the activity of one enzyme molecule - a measure of catalytic activity
34
Q

If the Michael is-menten model fits:

A

k2 = Kcat = volume/ [E]

35
Q

Vmax equation shit

A

Amount of times we can turn over a reaction in one second

36
Q

The ‘peak’ enzyme should have:

A
  • a high Kcat (ability to turn over a lot of substrate into product per second)
  • a low Km (low substrate concentration requires to ‘get up to speed’: high affinity for the substrate under the Michaelis- Menten assumptions
37
Q

What is the equation that shows the overall measure of enzyme activity?

A

Kcat/Km
- higher Kcat over Km, the greater effieicnty of enzyme

38
Q

Can make Kcat really _____ or Km really _—-

A

High
Low

39
Q

What is the fundamental way to quantify the activity of an ezyme?

A

To meausure the initial reaction rate, Vo at a range of different substrate concentrations

40
Q

What is the result of Vo at a range of different substrate concentrations and what is it described by.

A

Results in a hyperbola
- describes by the muchaelis-menten equation

BIOC192 (38 decks)

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