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Amino Acids - The Building Blocks of Life! Amino acids are molecules containing both the amide group – NH2 at one end of the molecule and carboxyl group COOH at the other end of the molecule. H2N – Δ – COOH The Δ part of the molecule represents various arrangements of atoms. There are just over 20 different types of Amino Acids. They join together in condensation reactions to form proteins. Joining Amino Acids H O I II N–R–C I I H OH H O I II + N–R*-C I I H OH The products H O H O I II I II N–R–C–N–R*-C + H2O I I H OH They are held together by a peptide link CONH (amide link) Proteins Proteins are made when thousands of amino acids join by condensation polymerisation. Very many different types of proteins can be made. ( compare number of possible words with 26 letters. > 20 Amino acids = many different proteins) Types of Proteins There are 2 main types – Fibrous and Globular Fibrous Proteins Long, thin linear molecules. Hydrogen bonding exists between the COOH and NH2 groups in near by chains or within the same chain. Examples – Keratin ( hair, wool, nails) Elastins ( lungs and arteries) Collagens ( skin and tissue) Globular Proteins They contain intermolecular bonding which can cause the molecule to become a spiral chain. They are involved in human biological processes. Examples – Enzymes, hormones and haemoglobin. Enzymes Enzymes are biological catalyst. They speed up the rate of reactions in living organisms. Enzymes are PROTEINS. They are very specific. They usually only catalyse 1 type of reaction. When enzymes are at the wrong temperature or pH – they are denatured ( destroyed). They work at optimum conditions – pH and T. Lock and Key Enzymes are so specific because of the “lock and key” model. The enzyme molecule will only let reactant (substrate) molecule which have the correct shape and orientation. They form an intermediate complex. The new substance forms and then leaves the enzyme surface – which can then be reused. When an enzyme is denatured the shape of the protein molecules, of the enzyme, has changed and the reactants no longer fit. Hydrolysis of Proteins This is the type of reaction where large protein molecules are broken down back into amino acids. Water is added. This is what happens to proteins when they are digested. This enables the smaller molecules to pass into the blood stream. Some amino acids can not be stored/made in the body, we have to take them, in our diet, on a regular basis – these are essential amino acids. They are essential for protein synthesis.