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SfM topics > Enzymes 1 > Flashcards

Enzymes 1 Flashcards

1
Q

Properties of an enzyme (3)

A
  • globular protein
  • biological catalyst
  • decrease activation energy
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2
Q

what is a co-factor?

A

non-protein part of the enzyme needed for activity

without them, proteins will not be able to carry out their functions and will unfold

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3
Q

In what 2 enzymes, are co-factors Fe2+ and Fe3+ found in?

A
  • catalase

- peroxidase

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4
Q

In what enzyme is the co factor K+ found in?

A

pyruvate kinase

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5
Q

In what enzyme is the co-factor Mg2+ found in?

A

Glucose-6-phosphatase

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6
Q

what is a co-enzyme?

A

complex organic molecule, usually produced from a vitamin (most vitamins in our diet produce enzymes) and help enzymes by acting as a “helper molecule”

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7
Q

What is the co-enzyme for the vitamin derivative, riboflavin?

A

FAD

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8
Q

what is the co-enzyme for the vitamin derivative, niacin?

A

NAD+

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9
Q

what is the co-enzyme for the vitamin derivative, pantothenate?

A

Coenzyme A

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10
Q

what is a prosthetic group?

A

co-factor covalently bound to the enzyme, crucial for enzyme’s function (non-protein component) which is physically linked to an amino acid in a protein

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11
Q

what is an apoenzyme?

A

the inactive enzyme which needs the co-factor to activate it

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12
Q

what is a holoenzyme?

A

“whole enzyme” (the apoenzyme PLUS the co-factor)

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13
Q

what do oxidoreductases do?

A

transfer electrons

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14
Q

what do transferases do?

A

group transfers

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15
Q

what do hydrolases do?

A

hydrolysis (transfer chemical groups of water)

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16
Q

what do lyases do?

A

form or add groups to double bonds

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17
Q

what do isomerases do?

A

transfer groups within molecules (forms isomers)

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18
Q

what do ligases do?

A

formation of C-C, C-S, C-O and C-N bonds coupled to cleavage, forms covalent linkages between molecules

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19
Q

do enzymes affect the equilibrium?

A

No effect

20
Q

do enzymes make a non-spontaneous reaction spontaneous?

A

no

21
Q

do enzymes increase the rate of a spontaneous reaction?

A

yes

22
Q

what delta G value will spontaneous reactions have?

A

negative (increase in entropy and decrease in enthalpy)

23
Q

what is energy barrier?

A

energy required to position chemical groups correctly (rearrange bonds)

24
Q

In a reaction coordinate diagram, what do transition states show?

A

the moment the chemical bonds are made and broken

25
Q

does the enzyme become part of the product?

A

No, the enzyme remains separate from the reaction

26
Q

what delta G value is needed for a reaction to happen?

A

Positive Delta G (energy input needed)

27
Q

when does catalysis happen?

A

when active site is complementary to transition state

28
Q

when is the point when activation energy is significantly lowered?

A

when substrate fits into the active site AND changes its shape. (both enzyme and substrate must change shape)

29
Q

what are the 3 factors which cause the enzyme to reduce the activation energy?

A
  1. entropy reduction (reducing disorder)
  2. desolvation (getting rid of water by replacing substrate-aqueous bonds with substrate-enzyme bonds)
  3. induced fit (conformation change occurs in enzyme)
30
Q

what are the 3 techniques which can be used to analyse an enzyme?

A
  1. enzyme kinetics
  2. mutagenesis
  3. 3D structure
31
Q

what will happen to the initial rate of reaction if the substrate concentration is increased?

A

higher initial rate of reaction

32
Q

when can initial velocity (v0) be calculated?

A

if we have excess substrate (initial substrate conc. doesn’t change)

33
Q

what is Vmax?

A

maximum reaction velocity (reaction can’t proceed faster)

34
Q

what does the Michaelis-Menten equation represent? (calculates initial velocity)

A
  • proposed model to account for hyperoblic curve when you plot V0 ( initial velocity) over substrate concentration
  • describes how reaction velocity varies with substrate concentration
35
Q

what does the first part of the M-M equation form and what type of reaction is it?

A

ES (enzyme/substrate complex) ; reversible reaction

36
Q

what does the second part of the M-M equation form and what type of reaction is it?

A

E + P ( enzyme and product made) reversible and slow

37
Q

what is the overall rate of reaction proportional to?

A

the amount of ES (enzyme/substrate complex)

38
Q

More ES would cause what to the rate of reaction?

A

it would increase rate of reaction ( and vice versa)

39
Q

what is the steady state?

A

when rate of formation of ES= rate of breakdown of ES

synthesis rate=degradation rate

40
Q

what is the rate limiting step of an enzymatic reaction?

A

breakdown of the ES complex to give free enzyme and product (since the more ES complex there is, the faster the second part of the reaction)

41
Q

what is the definition of Km (Michaelis constant)?

A

Km is the equivalent to the substrate concentration at which the initial reaction rate/velocity is half of the maximum reaction rate (1/2 Vmax)

42
Q

what is the better way of experimentally defining Vmax and Km?

A

drawing a Lineweaver- Burk plot (using the same data that was used to draw the M-M hyperbolic curve)

43
Q

what does Lineweaver-Burk plot show?

A

determines whether Vmax has been achieved, determine the Km and mechanism for enzyme inhibitors ( a straight line is obtained)

44
Q

what does a larger Km imply about ES complex?

A

less stable ES complex, less affinity between enzyme and substrate (bad affinity)

45
Q

what does a smaller Km imply about ES complex?

A

more stable ES complex, more affinity between enzyme and substrate (good affinity)

46
Q

the higher the Vmax, the higher the…

A

rate of enzyme ( faster the enzyme) and vice versa

SfM topics (21 decks)

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