1. 1 of the 3 macronutrients

2. Elemental Composition Proteins are made up of atoms of: Carbon C HydrogenH OxygenO NitrogenN and sometimes small amounts of Phosphorus (P), Sulphur (S) and Iron (Fe) Nitrogen is needed for growth. Proteins are the only nutrients that contain the element nitrogen. These elements are bonded together in small molecules called amino acids. Amino acids are bonded together into long chains called proteins

3. Basic Structure of protein – Amino Acids There are 20 different amino acids but each has the same basic structure. C = carbon atom H= Hydrogen atom NH 2 = Amino group COOH = Carboxyl group R = Variable group e.g. in the amino acid Glycine the R = H (one Hydrogen Atom) C H NH 2 RCOOH

4. Formation of a Peptide Bond C H NH 2 RCOOH C H NH 2 RCOOH

5. Biological Value of Protein The Biological Value of a protein is a measure of the quality of the protein and is expressed as a %. High Biological Value Contain all essential Amino Acids in the correct proportion for the bodies needs Complete proteins Animal sources Low Biological Value Lack some essential amino acids or do not contain them in the correct proportion Incomplete protein Plant sources

6. Sources of protein Animal protein Plant protein Cheese 26% Soya beans 40% Meat 20% Nuts 24% Fish 17% Rice 7 % Eggs 12% Peas 6% Milk 3% Beans ChickenPeas Lentils Cereals

7. Essential Amino Acids There are over 20 different amino acids. 8 are Essential Amino Acids that cannot be made by the body and must be eaten e.g. Lysine, Leucine, Isoleucine. There are 2 extra essential amino acids for children- Arginine and Histidine The rest are Non-Essential Amino Acids these can be made by the body e.g. Glycine, Cystine, Cysteine.

8. Supplementary Value of Protein When low biological value foods, that lack essential amino acids, are eaten together they can provide all the essential amino acids. The essential amino acids missing in one food can be made up for by being present in the other food and visa versa. This complementary value of protein means that vegans can get all the essential amino acids without eating animal food Example; Bread is lacking Lysine but is high in Methionine. Beans are lacking Methionine but high in Lysine. By eating beans on toast both essential amino acids are included in the meal.