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Biology UNIT 1
Part 3: Enzymes…read more

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Enzyme Structure
· Enzymes are globular proteins with a specific 3D
shape which is the result of the amino acid
· Only a small region (active site) is functional. It is
a small, hollow depression.
· Enzyme acts on a substrate, which has a
complementary shape to the active site so can
form an ES complex.
· Substrate is held by temporary bonds forming
between certain amino acids…read more

Slide 3

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Enzymes as catalysts lowering
activation energy
· For enzymes to work they must come into physical
contact with its substrate.
· It must have a complementary active site which
fits the substrate.
· The minimum amount of energy needed to
activate the reaction is called the activation
· Enzymes work by lowering this activation energy
level allowing reactions to take place at lower
temperatures.…read more

Slide 4

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Measuring the rate of an enzyme-
controlled reaction
· By measuring the formation of the products or
disappearance of substrate.
· Graphs:
1) lots of substrate
2) all active sites filled
3) substrate rapidly broken down to products
4) substrate decrease, product increase,
5) less substrates reach active site. Longer to be
broken down
6) rate of formation slows
7) graph flattens as all of substrate used.…read more

Slide 5

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Effect Of Temperature on Enzymes
· Increasing temperature, gives molecules more
kinetic energy so they move faster.
· This means there will be more collisions
between the substrate and active sites of
· This results in more enzyme-substrate
complexes being formed.
· This forms more products.…read more

Slide 6

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Effect Of Temperature on Enzymes
· If the temperature rises too high, the
molecules move so quickly that bonds holding
the tertiary structure break (i.e. H bonds)
· Enzymes lose its globular shape so the active
site is distorted.
· The substrate will no longer fit.
· The enzyme is now denatured and can't
regain its original shape.…read more

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