B3- Proteins and Mutations

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  • Created by: Lauren
  • Created on: 21-12-12 12:26


Proteins are made of long chains of amino acids. Their functions include:

  • structural, e.g. collagen
  • hormones, e.g. insulin
  • carrier molecules, e.g. haemoglobin
  • enzymes.

Each protein has its own number and sequence of amino acids. This results in different shapes of molecule.

It is estimated that there are over 19,000 different proteins in the human body, each with a particular function.


Enzymes are proteins which act as biological catalysts. They speed up chemical reactions, including those that take place in living cells, e.g. respiration, photosynthesis and protein synthesis. 

Enzymes are highly specific. Each one will only speed up a particular reaction. Enzyme activity, and therefore the rate of reaction, can be affected by changes in temperature or pH level.

The Lock and Key Mechanism

Each enzyme has an active site that only a specific reactant can fit into (like a lock and key). High temperatures and extremes of pH stop the lock and key mechanism working. 

When enzyme molecules are exposed to high temperatures or extreme pH, the following occurs:

1. The bonds holding the shape of the protein break.

2. The shape of the enzyme's active site is denatured (changed…


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