Protein Molecules

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  • Created by: acoke98
  • Created on: 20-03-15 11:47

Structure and Functions of Protein Molecules


- Organic Molecules:         a) carbohydrates

b) proteins

c) lipids

- All organic molecules contain the elements C, H, O.

- Nitrogen is found in all proteins.


- Proteins are required for:        a) the growth and repair of tissues

b) the production of enzymes

c) hormones

d) transportaion of O2 (haemoglobin)

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Amino Acid Structure of Protein Molecules

There are 20 R groups which produce 20 different amino acids.<-----  The general structure of an amino acid.

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Synthesis of a Dipeptide

  • Involves a condensation reaction... removal of a water molecule from 2 amino acid molecules.
  • Results in the formation of a peptide bond between the amino group of 1 amino acid and the carboxyl group of a second amino acid.
  • This is a reversible reaction... the peptide bond is broken on the addition of a water molecule --> hydrolysis.


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Primary Structure of a Protein Molecule


The number and sequence of amino acids in a polypeptide chain.

Different combinations of amino acids result in the formation of different protein molecules with different functions.

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Secondary Structure of a Protein Molecule


Weak H2 bonds form between the positively charged NH group and the negatively charged C=O group on either side of a peptide bond.

This results in the formation of an  -helix (alpha helix).

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Tertiary Structure of a Protein Molecule


The 3D shape of a protein molecule is the result of additional bonds (ionic, hydrogen, di-sulphide bridges) forming between the amino acid molecules in the polypeptide chain.

This twists and folds the protein into a unique shape.

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Quaternary Structure of a Protein Molecule


A protein molecule made up of 2 or more polypeptide chains.

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Proteins Structures

In a diagram it looks something like this:

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