proteins

• there are 20 different amino acids to form polypeptides
• amino acids are the basic monomer units that combine to make a polymer called a polypeptides
• amino acids are coded for by universal sequences (codons) in DNA
• globular proteins are soluble in water
• globular proteins have amore rounded, three dimensional shape
• globular proteins generally have metabolic functions
• fibrous proteins are insoluble in water
• fibrous proteins are long and narrow
• fibrous proteins generally have structural functions
• the primary structure of proteins = the sequence of amino acids in a polypeptide chain
• the secondary structure of proteins = formation of an a-helix or b-pleated sheets (hydrogen bonds - between N-H + C=O groups on amino acids)
• the tertiary structure of proteins = folding of protein chains into complex three dimensional shapes, stabilised by hydrophobic interactions, disulphide bridges and ionic bonds.
• quaternary structure of proteins = association of two or more polypeptides to form one functional unit, held together by non covalent bonds such as hydrogen bonding and electrostatic forces