Protein

Protein contains the following elements; Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulphur (S)

• Structure: Protein consists of repeating units of amino acids, of which there are approximately 20. Amino acids link together in polypeptide chains to form proteins. The basic structure of an amino acid is shown in the image.

Some polypeptide chains can become:

• twisted e.g. fibrous protein – keratin in hair, nails and feathers.
• folded e.g. globular proteins in enzymes and hormones
• folded and in addition have another chemical in the fold e.g. haemoglobin in red blood cells and glycoprotein on cell membranes.

Prions are proteins that do not fold correctly.  They can also cause similar proteins to fold incorrectly, and can lead to BSE, nvCJD and scrapie.

• Protein Food Sources:

Lean meat, egg white, fish, milk, soya, pulses, nuts & cheese. Protein is not stored in the body but is instead transferred to the liver and deaminated.

• Role of proteins in cell structure and metabolism:
  • Cell structure: Protein is found in cell membranes, hair /nails(keratin), myosin in muscles, skin.
  • Metabolism: The following are all made from protein - Enzymes (control chemical reactions), antibodies (fight infection), haemoglobin, hormones (regulate body functions e.g. insulin controls glucose levels in blood) and chlorophyll (photosynthesis).