Proteins

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  • Created by: araelw
  • Created on: 26-02-14 18:00

Proteins Overview

Proteins are polymers of Amino Acids, so are macromolecules. Some contain 100s of amino acids some contains several thousand. 

Functions: 

  • Structure of plasma membranes
  • Immune system
  • Structure of chromosomes

Amino acids are built around a carbon atom which is attached to:

  • a hydrogen atom
  • an amino group (-NH2)
  • a carboxyl group (-COOH)
  • An 'R' group which determines the nature of the amino acid. The 'R' represents other atoms in the molecule. 

Two amino acids joined together are known as a dipeptide, and many are polypeptides. When two or more peptide chains join to make a dipeptide or a polypeptide chain, a condensation reaction occurs. When they are broke apart, it is hydrolysis.

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Proteins Overview Part 2

Primary Structure: 

  • Specific sequence of amino acids. 

Secondary Structure:

  • A-Helix
  • B-pleated sheet
  • Held in place by hydrogen bonds 

Tertiary Structure: 

  • Further 'folding' to give a 3D shape. 
  • Held by hydrogen bonds between R-group and amino acids. 
  • Held by Disulphide Bridges between amino acids and R-groups containing sulphur. 
  • Held by ionic bonds between amino acids and positively/negatively charged R-groups.

Quaternary

  • Two or more polypeptide chains e.g haemonglobin (globular), collagen (fibrous). 
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