Louisgstq
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How can enzymes have an optimum temperature significantly below denaturing temperature? Surely, due to collision theory, a higher temperature will always increase rate of reaction right up until the enzymes denature?
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jamestg
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(Original post by Louisgstq)
How can enzymes have an optimum temperature significantly below denaturing temperature? Surely, due to collision theory, a higher temperature will always increase rate of reaction right up until the enzymes denature?
The bonds in the enzyme's active site begin to break under increases of temperature. These bonds in the active site are what hold its shape - the complementary shape, which allows the substrate to fit into it thus making the enzyme work. When these bonds break, the enzyme's tertiary structure begins to change and it makes the active site change slightly. Therefore increasing the temperature will cause more bonds to break, changing the active site's shape more and more.

The enzyme denatures when the substrate cannot fit into the enzyme.
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Louisgstq
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(Original post by jamestg)
The bonds in the enzyme's active site begin to break under increases of temperature. These bonds in the active site are what hold its shape - the complementary shape, which allows the substrate to fit into it thus making the enzyme work. When these bonds break, the enzyme's tertiary structure begins to change and it makes the active site change slightly. Therefore increasing the temperature will cause more bonds to break, changing the active site's shape more and more.

The enzyme denatures when the substrate cannot fit into the enzyme.
So, the more and more the shape of an enzyme's active site is changed, the less products that enzyme can catalyse per unit time?
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jamestg
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(Original post by Louisgstq)
So, the more and more the shape of an enzyme's active site is changed, the less products that enzyme can catalyse per unit time?
Pretty much

The enzyme becomes less effective as the temperature increases after its optimum.
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Louisgstq
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(Original post by jamestg)
Pretty much

The enzyme becomes less effective as the temperature increases after its optimum.
In that case, why is it not the case that every enzyme has the same (or similar) optimum temperature? I mean, polypeptides all have roughly the same strength of bond.
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jamestg
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(Original post by Louisgstq)
In that case, why is it not the case that every enzyme has the same (or similar) optimum temperature? I mean, polypeptides all have roughly the same strength of bond.
The primary structure of different enzymes are made up of different chains of amino acids. Thus giving each enzyme different properties, as the secondary, tertiary and quaternary structures are dependent on the primary structure. A different sequence of amino acids will give different shapes.

Due to the different sequences and numbers of amino acids - there will be different quantities of the different bonds. The types of bonds are - ionic, disulphide and hydrogen. Each bond will require different amount of energy, and so having different quantities of these three bonds will give different optimum temperatures.
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