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1BDS Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What are the six major classes of enzymes?

A 
oxidoreductases
transferases
lyases
hydrolases
isomerases
ligases
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2
Q

What do oxidoreductases do and give an example of one

A

catalyse redox reaction

e.g. lactate dehydrogenase

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3
Q

What do transferases do and give an example of one

A

transfer functional groups

aminotransferase

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4
Q

What do lyases do and give an example of one

A

add/remove atoms/functional groups to/from C=C/rings

decarboxylases

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5
Q

What do hydrolases do and give an example of one

A

cleave molecules by adding water

trypsin

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6
Q

What do isomerases do and give an example of one

A

catalyse the conversion of a molecule to one of its isomers

triose phosphate isomerase

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7
Q

What do ligases do and give an example of one

A

GLUE!!

join 2 molecules together

DNA ligase

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8
Q

What are co-factors and co-ezymes?

A

they help out enzymes that cannot carry out catalysis alone

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9
Q

What is the difference between co-enzymes and co-factors? Give examples of each

A

Co-factors directly assist with the reaction, e.g Mg2+ with DNA polymerase in DNA replication

Co-enzymes are organic carrier molecules which carry things needed for the catalysis, e.g. NADH - carry electrons, CoA - carry Acetyl groups

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10
Q

What is the difference between Vitamins and Minerals?

A

They are both types of co-enzymes and co-factors but:

Vitamins are organic, e.g. B3, B5

Minerals are inorganic, e.g. Mg2+, Ca2+

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11
Q

What is notable about pancreatic serine proteases?

A

The proteases in this group are all similar but catalyse hydrolysis at DIFFERENT POSITIONS in the peptide sequence due to structural differences in the polypeptides

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12
Q

What are the 3 well known enzymes that go through the serine protease mechanism?

A

CHYMOTRYPSIN
TRYPSIN
ELASTASE

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13
Q

What are the 6 types of enzyme regulation?

A 
Gene Expression 
Feedback loop
Feed forward activation 
Allosteric regulation 
Phosphorylation/Dephosphorylation
Proteolysis
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14
Q

What is meant by irreversible inhibition?

A

an irreversible inhibitor reacts with the enzyme making it enzymatically inactive and the active enzyme cannot be regenerated

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15
Q

What is meant by reversible inhibition?

A

A reversible inhibitor can bind to the enzyme and then be released leaving the enzyme in its original condition.

There are 3 types.

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16
Q

What are the 3 types of reversible inhibition? Briefly explain each of their action.

A

Competitive - compete with the substrate for the active site as it is similar in shape/structure. Increasing substrate competition decreases effect of inhibitor.

Non-competitive -binds to an allosteric site and changes conformation of active site. Cannot be overcome by increasing substrate inhibition.

Un-competitive - inhibitor binds to enzyme-substrate complex only - a binding site is created for the inhibitor when the substrate binds to the active site.

17
Q

What are the 3 types of enzymes used as drug targets?

A

INHIBITORS - ACE is used to treat hypertension

FALSE SUBSTRATES - producing an abnormal metabolite,
FLUOROURACIL

PRO-DRUGS - an inactive precursor is given which is then converted into its active form by the enzyme, CORTISONE to HYDROCORTISONE

18
Q

How are enzymes used a markers for disease?

A

Enzymes are generally intracellular and predoninantly located in one/a small number of organs so their release into the bloodstream can be used as a marker of cell damage/cell death

19
Q

What are isozymes?

A

isozymes are isoforms of enzymes which catalyse the same reaction but have different properties and structure.

20
Q

What are the 3 known possibilities for isozyme formation?

A

They may be:

  • synthesised during different stages of foetal/embryonic development
  • present in different tissues
  • present in different cellular locations
21
Q

Give details of the isozymes of Creatine Kinase

A

CK is a dimeric protein which binds to the muscle sarcomere.

MM = skeletal muscle
BB = brain
MB = heart

indicates skeletal muscle damage

22
Q

Give details of the izosymes of Lactate Dehydrogenase

A

Enzyme has 4 subunits so there are 5 different combinations.

Found in heart, kidneys, RBCs, Liver and Skeletal Muscle.

increase in LDH indicates tissue damage + location. Also used to look at disease progression.

1BDS Biochemistry (5 decks)

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