2.1.2 - Proteins

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  • Made from long chains of amino acids. Dipeptide is formed when two amino acids join together. A polypeptide is formed when two or more amino acids join together. Proteins are made up of many polypeptides. 
  • Amino acids are made up of a carbon surrounded by a hydrogen, an NH2 group, a carboxyl group and an R-group. The r group is a variable group which is different on different amino acids. 
  • Proteins are joined together by peptide bonds to form dipeptides and polypeptides. A molecule of water is released when this reaction takes place. This is a condensation reaction. The reverse of this reaction (i.e. breaking the peptide bonds) adds a molecule of water. This is called a hydrolysis reaction. 

Proteins have four strcutural levels:

  • Primary- Sequence/order of amino acids in the polypeptide chain. Held together by peptide bonds
  • Secondary- The way the hydrogen bonds between


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