proteins
- Created by: kierasanghera
- Created on: 21-05-16 20:58
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- proteins
- amino acids
- made up of an amine group, a caboxyl group and a variable R group
- all contain carbon, hydrogen, oxygen, nitrogen (some contain sulphur)
- amino acids join to form a peptide bond (using a condensation reaction)between the carboxyl group of one and the amine group of another, with a water molecule being lost
- primary structure
- amino acid sequence
- determined by a gene that codes for the polypeptide
- secondary structure
- become twisted or coiled
- fold into either alpha helix or beta pleated sheet
- hydrogen bonds hold coils in place
- tertiary strcuture
- folding of secondary structure gives more complex 3D globular shape
- shape is specific to the function of the polypeptide
- structure held in place by: Ionic bonds, hydrogen bonds, disulphide bonds and hydrophobic and hydrophilic interactions
- quaternary structure
- association of different polypeptide chains bonded together to form intricate shapes
- globular
- curl up into a ball shape, e.g. haemoglobin, have metabolic roles
- generally have hydrophobic (inside) and hydrophilic (outside)parts
- end to be water soluble as hydrophillic r groups allows water to surround them
- heamoglobin
- oxygen carrying pigment found in red blood cells
- has four polypeptides, two alpha globin and two beta globin
- 3 degree structure stabilised by hydrophobic interactions in the centre
- each polypeptide having a heam group
- fibrous
- form long strands that are usually insoluble, have structural roles e.g keratin and collagen
- collagen
- 3 identical polypeptide chains wound into a triple helix (held together by hydrogen bonds)
- around 1000 amino acids long per polypeptide
- sequence of polypeptide chains are staggered so glycine is found at every position along the triple helix
- adjacent molecules of collagen held together by covalent bonds formed between carboxyl group of one amino acid and the amine group of another
- amino acids
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