Biology enzymes

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Enzymes 1

Enzymes are BIOLOGICAL CATALYSTS

They SPEED up reactions by LOWERING ACTIVATION ENERGY

Enzymes are PROTEINS

They have a 3D shape called the ACTIVE SITE

Lock and Key hypothesis:

Substrate fits right into the active site like a lock and key

Induced fit model:

The substrate forces the active site to change shape

To form the ENZYME SUBSTRATE COMPLEX

Why are enzymes SPECIFIC?

Active site is COMPLIMENTARY to one substrate only

They are proteins

They have a certain shape due to folding in the TERTIARY structure

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Enzymes 2

PH:
EXTREMES of PH will DENATURE enzymes - H or IONIC bonds are broken
Active site changes SHAPE
Substrate NO LONGER FITS / no more ENZYME-SUBSTRATE COMPLEXES form

Temperature:
As temperature increases molecules have more KINETIC ENERGY
They have more COLLISIONS
More ENZYME-SUBSTRATE COMPLEXES form
Up to the OPTIMUM temperature
Then......
Enzyme DENATURES
Breaks H bonds
Active site changes SHAPE
No more ENZYME-SUBSTRATE COMPLEXES form

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Enzymes 3

Enzyme concentration:
As concentration increases so does rate
More ENZYME-SUBSTRATE COMPLEXES form
As there are a higher CHANCE of COLLISIONS
Then ....
Rate stays CONSTANT
Because....
Something else LIMITS it e.g. Substrate concentration

Substrate concentration:
As concentration increases so does rate
More ENZYME-SUBSTRATE COMPLEXES form
As there are a higher CHANCE of COLLISIONS
Then ....
Rate stays CONSTANT
Because....
All the active sites are OCCUPIED
This is knows as ACTIVE SITE SATURATION

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Enzyme inhibition

Inhibition:
When something directly or indirectly interferes with the functioning of the active site of an enzyme
2 types of reversible inhibitor:

Competitive:
The inhibitor competes with the substrate to fit in the active site
It has a similar molecular shape to the substrate
It occupies the enzymes ACTIVE SITE
So substrate can no longer fit in the active site

Non- competitive inhibitors:
The inhibitor attaches to the ALLOSTERIC site
This alters the SHAPE of the active site
The substrate NO LONGER FITS
The enzyme is DENATURED
No more ENZYME-SUBSTRATE COMPLEXES form

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