Rates of Reaction
Catalysts - Enzymes -
Temperature and pH.
What is an Enzyme?
An enzyme is a protein
Enzymes are used by living cells as catalysts.
Enzymes are very specific catalysts.
This means that one particular enzyme will act as a
catalyst for one particular reaction but nothing else.
An enzyme will work best
at a particular temperature and
called its optimum conditions. Enzymes usually work best
in warm conditions (around 40 °C) unlike chemical catalysts
which often work best when they are very hot.
A graph of enzyme
activity plotted against temperature
is shown below. Enzyme activity is a
measure of how well an enzyme works as a catalyst.
°C, the enzyme begins to stops working.
Above this temperature the
shape of the enzyme changes and it is said to denature.
graph of enzyme activity
against pH would have
a similar shape but the peak (the optimum conditions)
would be at a different pH for different enzymes.
Pepsin in the stomach
works best at pH = 2.
Amylase in the mouth works best at pH = 7.
Links Catalysts and Energy Enzymes Revision Questions
gcsescience.com The Periodic Table Index Enzyme Quiz gcsescience.com
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