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Biochemistry > Enzymes 2 > Flashcards

Enzymes 2 Flashcards

1
Q

What are co-factors?

A

Non-protein factors which are essential for enzyme activity

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2
Q

What are coenzymes?

A

Carbon containing cofactors (organic) derived from water soluble vitamins

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3
Q

What are prosthetic groups?

A

Tightly bound cofactors

some covalently bound

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4
Q

What are co-substrates?

A

Loosely + transiently bound cofactors

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5
Q

What is a haloenzyme?

A

Enzyme w/ prosthetic group

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6
Q

What is an apoenzyme?

A

Enzyme w/out prosthetic group

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7
Q

What are the 3 cofactor examples and their roles in catalysed reactions?

A

Iron & copper
- REDOX

Zinc
-helps bind NAD

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8
Q

What are the 4 coenzyme examples?

A

Biotin

Coenzyme A

NAD
-carries electrons
FAD
-carries electrons

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9
Q

What are the 3 prosthetic groups?

A

Heme

Flavin

Retinal

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10
Q

What is the overall pattern in the structure of coenzymes?

A

Adenine + ribose + 2 phosphates + vitamin

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11
Q

What is the general structure of a cofactor?

A

Common motif of adenine + ribose + another group

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12
Q

What do coenzymes do?

A

Bind to active site of enzyme + are involved in catalysis

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13
Q

By how much to enzymes increase the rate of reaction?

A

10^5 to 10^17 fold

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14
Q

What are steady-state kinetics?

A

The state reached a short time after mixing an enzyme + a substrate

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15
Q

What is a katal?

A

SI unit

Amount of enzyme that gives 1 Mol/sec

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16
Q

What is added to an enzyme assay to stop a reaction?

A

Acid

- denatures enzyme

17
Q

How can product be measured in a direct assay?

A

If P is coloured - measure colour change via spectrophotometer

P could fluoresce or be a gas

Measure continuously

18
Q

How is rate of reaction measured in a discontinuous direct assay?

A

Stop reaction (using acid/alkali) at set time points + measure P or S

19
Q

What are the 4 factors that affect enzyme rate?

A

Conc of enzyme
Conc of substrate
Temp
pH

20
Q

When is there a linear relationship between rate + amount of enzyme?

A

When substrate is not limiting or product in excess

21
Q

What happens as substrate conc increases?

A

Rate increases by lesser amounts
–> eventually reaches plateau
= Vmax

22
Q

What is the Michaelis-Menten equation?

A

V = Vmax[S] / (Km +[S])

23
Q

What is Km?

A

Michaelis constant
= the [S] that gives 1/2 maximal rate
= 1/2Vmax

24
Q

The higher the Km…?

A

The higher the [S] needed to reach Vmax

25
Q

Why could the real Km of some enzymes be different to those found in experiments?

A

In labs, artificial substrates added to enzymes

- could be different for natural substrates

26
Q

What is the issue with the Lineweaver-Burk equation rearrangement?

A

The lowest [S] gives the highest values on the graph

–> but lowest [S] are most inaccurate values

27
Q

Why does reaction rate increase w/ temp up to optimum?

A

Increases enzyme’s internal mobility
–> allows substrate to enter + exit active site
as allows formation of transition state complex

28
Q

Why does rate of reaction decrease w/ temp beyond optimum?

A

Enzyme too mobile
–> loses structure
= denatured

29
Q

What are isozymes?

A

Different forms of enzymes w/ same function but diff structure

30
Q

How does pH affect enzymes?

A

H+ ions bind to/are released from carboxyl groups + amino groups present in side chains of amino acids
–> charges on amino acids are important for structure

31
Q

What are the water soluble vitamins?

A 
B1, B2, B3, B6 + B12
Vit C
Folic acid
Biotin
Pantothenic acid
32
Q

What are the water insoluble vitamins?

A

A
D
E
K

33
Q

Which type of vitamins form co-factors?

A

Water soluble

34
Q

Which test is used to measure glucose?

A

Hardings test

in a discontinuous direct assay
(measure green colour)

Biochemistry (14 decks)

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