A-LevelBiologyBiological molecules9700/12 · May/June 2024 · Q131 Mark
Which row correctly describes haemoglobin? [Table with four columns describing aspects of 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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