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Enzymes

Topic 2
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5
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Biology SL

Due to the break of intramolecular bonds and the loss of the
active site’s shape = denaturing

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pH
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Many amino acids are charged

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A substrate must have the opposite charge when it is in the active
site of an enzyme, in order for the enzyme to have catalytic action

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As pH decreases, the concentration of hydrogen ions increases
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Hydrogen ions bind to negative side of the active site and
make it neutral
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The enzyme cannot hold positive substrates

As pH increases, the concentration of hydroxyl ions increases
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Hydroxyl ions bind to the positive side of the active site
making it neutral
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■

The enzyme cannot hold negative substrates

Changes in pH make enzyme less efficient and in extreme situations
they become completely inactive or they change shape and they
denature

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Different enzymes are effective in different pH
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In the human body, the enzymes are most active in a nearly
neutral environment
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There are exceptions, like pepsin which can be found
in the stomach and works better in an acidic pH

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Substrate concentration
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The higher the substrate concentration, the greater the likelihood of
a substrate to find the active site
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More reactant molecules = increased molecular collision

Enzymes have a maximum rate at which they can work
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If every enzyme molecule is working as fast as possible,
adding more substrates to the solution will not increase the
rate any further

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The enzymes do not denature because of the increase, they
just continue working at the same rate

2

Enzymes

Topic 2

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