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Biochemistry 1 BB10003 > lecture 6 - enzymes > Flashcards

lecture 6 - enzymes Flashcards

1
Q

What are cofactors?

A

metal ions

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2
Q

What are coenzymes?

A

organic molecules

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3
Q

What is the difference between cosubstrates and prosethetic groups?

A

cosubstrates are transiently associated with the enzyme whereas cofactors are associated with the enzyme

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4
Q

What is a holoenzyme

A

catalytically active enzyme - cofactor complex

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5
Q

What is a apoenzyme

A

inactive enzyme (absence of the cofactor)

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6
Q

where can we get cofactors?

A

The vitamins we eat

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7
Q

what are the units to measure specific enzyme activity?

A

Umol/min/mg protein

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8
Q

enzyme unit

A

amount which gives 1 Umol product/ min

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9
Q

Katal (SI unit)

A

Amount which gives 1Mol/sec

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10
Q

What is the Michaelis - Menton equation?

A

Vmax(S) / Km +(s)

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11
Q

What is an assumption of the steady state diagram?

A

K-1 is greater than k2. Therefore there is an equilibrium between (ES) and (E) + (S)

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12
Q

What is Km?

A

The substrate concentration at which the reaction rate is half of the maximal value

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13
Q

Unit for Km?

A

M

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14
Q

What is Vmax?

A

Reaction rate when the enzyme is fully saturated by the substrate

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15
Q

What is the units for Vmax?

A

Umol/min

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16
Q

What is Kcat?

A

Equal to K2. It measures. the number of substrate molecules “ turned over” by enzyme per second

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17
Q

what is the unit for Kcat?

A

1/second

18
Q

What can be inferred when an enzyme has a small Km?

A

Achieves maximal catalytic efficiency at low substrate concentrations

19
Q

What is Kcat equal to?

A

K2

20
Q

What does K2 measure?

A

number of molecules ‘turned over’

21
Q

What is Ks

A

The dissociation constant

22
Q

What is the formula for KS?

A

k-1 divided by K1

This equals; Enzyme times substrate divided by the enzyme substrate complex.

23
Q

What does Vo represent on a Michaelis Menton equation?

A

The initial rate

24
Q

What can we assume due to the steady state assumption?

A

The rate of change of The enzyme substrate complex = 0

25
Q

How to measure assays ?

A

rate of initial product// disappearance of substrate

26
Q

What is a discontinuous assay?

A

reaction stopped and another enzyme added

27
Q

What is a direct assay?

A

Real time detection

28
Q

What are coupled assays?

A

measure a reaction which is easy to measure which links it to the main reaction which cannot be measured

29
Q

What is the rate of product creation equal to?

A

= K2 times the concentration of the Enzyme substrate complex

30
Q

What is the dissociation constant assuming?

A

The enzyme substrate complex does not change over the Time of the assay

31
Q

What is Km known as?

A

The Michaelis constant

32
Q

what happens when the substrate concentrations are low

A

substrate concentration small relative to Km.

simplified to V = Vmax/Km ( linear relationship)

33
Q

What happens when substrate concentrations are high?

A

Km is relatively small , compared to substrate concentrations. v = Vmax.

34
Q

When does Km differ?

A
  • Differ with enzyme type

- differs with temp and ph

35
Q

How can we consider Km?

A

When enzyme binds substrate tightly has a low Km value. Inverse affinity for the substrate.

36
Q

How can we work out Vmax?

A

K2 times starting enzyme concentration// Kcat times starting enzyme concentration

37
Q

What are the two graphs to analyse the Michaelis Menton equation?

A

Lineweaver burk plot and the Hanes Woolf equations

38
Q

How to get the Lineweaver burk plot?

A

take the reciprocal of everything

39
Q

Why is the line weaver burk plot not accurate ?

A
  • Lots of incorrect crowded points and only one or two points at the top of the graph
40
Q

what is the Hanes Woolf plot?

A

rearrangement of the Michaelis Menton equation

41
Q

What are cofactors?

A

transiently associated with the enzyme

42
Q

What are prosthetic groups?

A

associated with the enzyme

Biochemistry 1 BB10003 (18 decks)

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