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Science for Medicine > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What is a cofactor?

A

Non-protein component of enzymes that are needed for activity

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2
Q

What is a coenzyme?

A

A complex organic molecule usually formed from vitamins

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3
Q

What is a prosthetic group?

A

Cofactor covalently bound (or very tightly associated) to an enzyme

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4
Q

What is an apoenzyme?

A

Protein component of an enzyme containing a prosthetic group

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5
Q

What is a holoenzyme?

A

The whole enzyme

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6
Q

How to enzymes catalyse reactions?

A

They increase the rate of spontaneous reactions, lower activation energy and accelerates movement towards equilibrium

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7
Q

What do spontaneous reactions contain?

A

An energy barrier

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8
Q

What happens as [S] increases?

A

The initial velocity increases up to Vmax

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9
Q

What is the shape of the initial rate in a [S] vs Vo graph when the [enzyme] is much lower than [substrate]?

A

Hyperbolic

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10
Q

What is Vo?

A

The initial reaction velocity that is the steady state of a reaction

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11
Q

What is Vmax?

A

The maximum reaction velocity, when all the active sites are saturated by substrate

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12
Q

What is Km?

A

Michaelis constant

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13
Q

What is the function of Km?

A

Measures an enzymes affinity for its substrate

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14
Q

What is the affinity when Km is low?

A

High

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15
Q

What is the affinity when Km is high

A

Low

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16
Q

What does the Michaelis-Menton (M-M) equation tell us?

A

Km= 1/2Vmax= (k-1 + k2)/k1

17
Q

What does k1 determine?

A

The overall rate

18
Q

What is k2?

A

It is slower than k1 and is reversible

19
Q

What is the M-M equation useful for?

A

Measuring Vo and Vmax

20
Q

What are the 3 types of enzyme inhibitors?

A

Competitive, non-competitive and uncompetitive

21
Q

What is a competitive inhibitor?

A

An inhibitor that binds non-covalnetly to the active site. Their affect is overcome by high substrate concentrations and they mimic the substrate. They do not affect Vmax

22
Q

Can Vmax still be achieved in competitive inhibition?

A

Yes as it is overcome by high substrate concentrations

23
Q

What affect does competitive inhibition have on Km?

A

It increases Km, decreasing affinity for the substrate

24
Q

What is a non-competitive inhibitor?

A

It is an inhibitor that binds non-covalnety to the allosteric site. They are not overcome by high substrate concentrations

25
Q

What affect does non-competitive inhibition have on Km?

A

It is unchanged as substrates can still bind to the active site

26
Q

What affect does non-competitive inhibition have on Vmax?

A

Vmax decreases as the inhibitor can’t be displaced

27
Q

What is an uncompetitive inhibitor?

A

An inhibitor that binds to the complex formed by the enzyme and substrate

28
Q

What affect does uncompetitive inhibition have on Km?

A

It decreases

29
Q

What affect does uncompetitive inhibition have on Vmax?

A

It decreases

30
Q

What is an enzyme assay?

A

A method of measuring enzyme activity for clinical diagnosis

31
Q

What regulates enzyme activity?

A

Allosteric effectors

32
Q

What are allosteric effectors?

A

They can be inhibitors or activators that enable changes in the ICE and ECE which changes the flow of metabolic pathways

33
Q

What are allosterically-regulated enzymes?

A

Multimeric proteins in which a conformational change in one of the polypeptides affects the whole the protein

34
Q

What is a multimeric protein?

A

Many polypeptides held together

35
Q

What is the shape of the initial reaction rate against [S] graph fro allosterically-regulated enzymes?

A

Sigmoidal

36
Q

What is an example of a reaction that would produce a sigmoidal curve?

A

When oxygen binds to haemoglobin

37
Q

What is reversible covalent modification?

A

Modification in amino acid side chains which affects enzyme activity

Science for Medicine (19 decks)

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