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BIO1332 - Biochemistry > Enzyme and Co-Enzymes > Flashcards

Enzyme and Co-Enzymes Flashcards

1
Q

What is the importance of an enzyme?

A
  • Natural catalysts and carry out all the reactions in the cell
  • Many inherited diseases are caused by mutations in key enzymes
  • Measurement of certain enzymes in blood is used to diagnose disease
  • Used commercially in food products and in detergents
  • Used in drug synthesis
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2
Q

What are the 6 classes that enzymes can be split into?

A
  • Oxidoreductase
  • Transferase
  • Hydrolase
  • Hydrolase
  • Lyase
  • Isomerase
  • Ligase
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3
Q

What is the function of an oxidoreductase in a chemical reaction?

A

Oxidation-reduction in which oxygen and hydrogen are gained or lost

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4
Q

What is the function of a transferase in a chemical reaction?

A

Transfer of functional groups

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5
Q

What is the function of a hydrolase in a chemical reaction?

A

Hydrolysis (addition of water)

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6
Q

What is the function of a lypase in a chemical reaction?

A

Removal of groups of atoms without hydrolysis

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7
Q

What is the function of an isomerase in a chemical reaction?

A

Rearrangement of atoms within a molecule

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8
Q

What is the function of a ligase in a chemical reaction?

A

Joining of two molecules (using energy normally derived from the breakdown of ATO)

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9
Q

Give an example of an oxidoreductase enzyme:

A

Cytochrome oxidase, lactate dehydrogenase

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10
Q

Give an example of a transferase enzyme:

A

Acetate kinase, alanine deaminase

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11
Q

Give an example of a hydrolase enzyme:

A

Lipase, sucrase

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12
Q

Give an example of a lyase enzyme:

A

Oxalate decarboxylase, isocitrate lyase

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13
Q

Give an example of an isomerase enzyme:

A

Glucose-phosphate isomerase, alanine racemase

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14
Q

Give an example of a ligase enzyme:

A

DNA ligase, Acetly-CoA synthetase

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15
Q

Arrehenius equation:

A

k = Ae^-DG‡/RT

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16
Q

Should the DGreaction be positive or negative for the reaction to be favourable?

A

Positive

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17
Q

Finish the sentence: The higher the activation energy, the ….

A

slower the reaction

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18
Q

What is the Arrhenius equation showing?

A

The relationship between activation energy and the reaction rate constant

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19
Q

What is the transition state?

A

Transient high-energy species in the conversion of substrate to product

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20
Q

What is the speed of the reaction dependent on?

A

The activation energy

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21
Q

What does the catalyst?

A

Reduce the activation energy

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22
Q

Does a catalyst lower the activation energy?

A

Yes

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23
Q

Does a catalyst change the energy of a reaction?

A

No

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24
Q

Can a catalyst make a thermodynamically unfavourable reaction become more favourable?

A

No

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25
Can a catalyst change the position of equilibrium?
No
26
Can a catalyst speed up how quickly the reaction reached equilibrium?
Yes
27
What is the role of an enzyme as a catalyst?
- Provides a specific environment for substate so reaction is more favourable - Has pocket which is know as the active site - Lowers the activation energy - Enzyme is regenerated - ES AND EP are reaction intermediates
28
Where does the transition state take place?
in the intermediate stage of a reaction
29
What is bad for the catalysis?
Tight binding to wither substrate or products
30
When is it important for the catalyst to bind tightly?
During transistion state
31
What happens during transition state?
- The same forces that stabilise protein folding also stabilise the ES‡ - Some enzymes form transient covalent bonds - binding energy is formed during complex formation - Enzyme is complimentary to transient state
32
Does an acid a donor or accepter to a proton?
Donor
33
Define co-enzyme:
Non-protein organic molecules required for catalysis
34
Example of a co-enzyme:
biotin, NAD+, FAD
35
Define co-factors:
Inorganic substances that are required for catalysis
36
Example of co-factors:
metal ions Fe2+, Zn2+ , Cu2+, Mg2+
37
Define holoenzyme:
Combination of protein and co-enzyme/co-factor
38
Define apoenzyme:
The protein alone without the co-enzyme/ co-factor
39
What do co-enzymes and co-factors allow enzymes to access?
Chemistries that amino acid side chains cannot access
40
How can disease result from co-enzymes?
Due to a deficiency
41
What coenzyme mediated a carboxylation reaction?
Biotin
42
What coenzyme mediated an alkylation reaction?
B12
43
What coenzyme mediated an acyl transer reaction? (2)
Coenzyme A | Lipoic acid
44
What coenzyme mediated an oxidation-reduction reaction? (2)
Flavin coenzyme | Nicotinamide coenzyme
45
What coenzyme mediated an amino group transfer reaction?
Pyridoxal phosphate
46
What coenzyme mediated a one-carbon transfer reaction?
Tetrahydrofolate
47
What coenzyme mediated an aldehyde transer reaction?
Thiamine pyrophosphate
48
What are the three enzyme mechanisms?
- General acid-base catalysts - Metal ion catalyse - Covalent catalysis
49
What is a general acid-base catalysts?
Enzymes stabilise unstable charged transition states by transferring protons to and from them (Decreasing their free energy)
50
What do amino acid side chains act as in acid-base catalysts?
Weak proton donors or acceptors
51
Describe the RNAse mechanism:
- His12 acts as general base = takes proton from RNA 2'-OH making a nucleophile which attacks the phosphoryl group - His119 acts as general base = promotes bond scission - 2',3' cynic intermediate is hydrolysed through revers of first step (water replaces leading group - His12 is the acid - His199 acts as the base
52
What type of enzyme mechanism is the RNAse mechanism?
Acid-base catalyst
53
What is a metal ion catalysis?
``` Interactions between an enzyme bound metal and substate can: orient a substate for reaction or stabilise charged reaction states or mediate oxidation-reduction reaction ```
54
What type of enzyme mechanism is the carbonic anhydrase doing?
Metal ion catalysis
55
What does the carbonic anhydrase assist in a reaction?
Zn2+ forms a bond with an OH- ion in the active site.
56
Why do water molecules readily dissolve?
To give protons
57
What is a covalent catalysis?
Formation of transient covalent bond between enzyme and substrate
58
Why do covalent complex undergo a reaction?
Regenerate the free enzyme
59
Serine protease has a catalytic triad at the active site. What are the amino acids?
Aspartate, histidine and serine
60
What type of enzyme is serine protease?
endoproteases
61
What is meany by endoprotease enzyme?
hydrolyse the peptide bond
62
What is the protease mechanism?
A mixture of acid-base catalysis and covalent catalysis
63
Which amino acid is the most important in the serine protease catalytic triad?
Serine
64
Which amino acids acts as the nucleophile in the serine protease?
Serine
65
What do the histone and aspartic acid provide to serine?
Makes serine more nucleophilic
66
What are the 6 steps in protease mechanism?
- ES complex (Michaelis complex) - First transition state (Tetrahedral intermediate) - Acyl enzyme intermidate - Acyl enzyme water complex - Second transition state - Tetrahedral intermediate - Free enzyme
67
What is meant by serine protease specificity?
Each enzyme has different pockets: Trypsin/Chymotrypsin/Elastase
68
What does the trypsin do?
Cleaves after Arg and Lys residues and has an Asp residue in the binding pocket
69
What does the chymotrypsin do?
cleaves after aromatic residue and has a serine in the binding point
70
What does the elastase fo?
cleaves after small hydrophobic residue e.g glycine, alanine or valine

BIO1332 - Biochemistry (19 decks)

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