1) primary structure =amino acid sequence2)secondary structure=hydrogen bonds hold the amino acid sequence in an alpha helix or bets pleated sheet3)tertiary structre= twisted and folded into a complex, 3D structure, held in place by disulphide bridges, ionic and hydrogen bonds4) quaternary structure=multiple polypeptide chainsThe structure of a protein relates to function
Food test for proteins
1)add a few drops of biruet reagent (sodium hydroxide and copper (II) sulphate) to the test sample2)blue to purple indicates the presence of peptide bonds (protein)
How can you make results more quantitative?
Use a colorimeter (more accurate as results are semi quantitative)
globular proteins

-form spherical ball shapes-compact structure -carry out metabolic functions-eg enzymes and haemoglobin
Haemoglobin structure
fibrous proteins

-structural proteins-form long strands/chains which run parallel to eachother-linked by cross bridges -strong and stable-eg. Collagen
