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Protein molecules that are biological catalysts
· Intracellular enzymes act inside of cells. Some examples of
these are ATPases and hydrolases.
· extracellular enzymes act outside of cells. For example
digestive enzymes in the alimentary canal (amylase)
· enzymes are globular proteins.
· They are soluble in water because their hydrophilic R groups
are on the outside of the molecule.
· Enzymes possess an active site. This is where the substrate
· The substrate is held in place by temporary bonds that form
between substrate and some of the R groups. The combined
structure is called the enzyme-substrate complex
· Induced fit is when the shape of the enzyme changes when
it binds with its substrate.…read more

Slide 3

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The enzyme may...
1. Catalyse a reaction in which the substrate
molecule is split into two or more molecules.
2. Catalyse the joining together of two
molecules (for example linking amino acids)
3. As a result one, two or more products are
4. These products leave the active site and the
enzyme is unchanged by the process.…read more

Slide 4

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Activation energy
· The substrate will not be converted to a product
unless it is temporarily given some extra energy, this
is activation energy.
· You can increase the amount of energy by increasing
the temperature.
· If you raise the temperature above 40 degrees
however molecules in our body start to become
damaged (proteins etc) therefore enzymes help to
reduce this as they make reactions quicker without
having to increase the temperature. They reduce the
activation energy.
· Enzymes do this by holding the substrate in such a
way that their molecules can react more easily.…read more

Slide 5

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The course of a reaction
· During a reaction the rate at which the
enzymes work is a lot faster at the beginning
and then slows down.
· This is because at the beginning there is a lot
of substrate molecules. So every enzyme
molecule has a substrate in its active site.
· Initial rate of reaction is the rate at the
beginning when the reaction is at its faster.…read more

Slide 6

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Enzyme inhibitors
· Competitive inhibition is when it is more likely that
an inhibitor will bond with the enzyme rather then
the substrate.
· this is reversible because it can be reversed by
increasing the concentration of substrate.
· Irreversible inhibition is when the inhibitor is
permanently bonded to the enzyme.
· Non competitive inhibition is when an inhibitor
bonds with a different part of the enzyme. This can
disrupt the arrangement of bonds holding the
substrate in place. It can be reversible inhibition or
irreversible inhibition.
· Inhibitors can react as metabolic poisons…read more

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