Haemoglobin (structure)

Haemoglobin - protein = polymer and amino acids = monomers

Structure of amino acid: Carboxylic acid group Amino group

20 different amino acids - all different R group

2 amino acids = dipeptideHydrogen atom taken from amino group of one amino acid and an Oxygen & Hydrogen atom taken from carboxylic group of the other amino acid

H+OH removed = water moleculeCondensation reaction

Bond formed = peptideAmino acids join together = polypeptide

Primary Structure:Number and sequence of amino acids in the polypeptide chainHaemoglobin = 4 polypeptide chains2 chains identical = alpha chains2 chains identical = beta chainsEach chain = 100+ amino acids

Secondary Structure:Chains so long - twist and coil = makes different shapesWeak hydrogen bonds  form between polypeptide bonds in different parts of chainPolypeptide chains fold into shapes:Alpha helixBeta pleated-sheet

Tertiary Structure: (overall shape)Polypeptide chains can fold again = complex 3D shapeHeld in place by bonds - form between R groups in amino acidsDifferent kinds of bonds hold together:Weak hydrogen bondsStronger Disulfide bondsCysteine - amino acid with sulfur in R group2 cysteine molecules join together = disulfide bond between 2 sulfur atomsI

Quaternary Structure:Proteins with more than one polypeptide chain = quaternary structureThe way polypeptide chains fit together

4 bond types in tertiary structure: Hydrogen Hydrophobic interactions Ionic Disulfide

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