A-LevelBiologyBiological molecules9700/12 · May/June 2016 · Q81 Mark
Which set of statements correctly describes haemoglobin?
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Afour polypeptide chains, each containing a haem group; iron ions can associate with oxygen forming oxyhaemoglobin; in each chain, hydrophobic R groups of amino acids point towards the centre of the molecule; at 50% saturation, two oxygen molecules are transported by the molecule
Bpolypeptide chains interact to produce a globular chain; each chain contains a haem group of amino acids surrounding an iron ion; consists of two identical alpha chains and two identical beta chains; each chain can transport an oxygen molecule
Cpolypeptide chains interact to produce an almost spherical molecule; an iron ion is present within each haem group; quaternary structure has two alpha chains and two beta chains; each molecule can transport a total of four oxygen atoms
Dpolypeptide chains produce a loose helical shape, which folds to form a spherical molecule; iron ions in the molecule can bind reversibly with oxygen; in each chain, hydrophobic R groups of amino acids surround the iron ion; each molecule can transport a total of eight oxygen atoms
✓ Correct answer
A: four polypeptide chains, each containing a haem group; iron ions can associate with oxygen forming oxyhaemoglobin; in each chain, hydrophobic R groups of amino acids point towards the centre of the molecule; at 50% saturation, two oxygen molecules are transported by the molecule
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