Which row gives the correct description of haemoglobin?
- 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