Edexcel A Level Chemistry:复习笔记6.2.8 Haemoglobin

Haemoglobin

 

  • Haemoglobin is one of nature's complexes using a transition metal ion
  • The haem molecule is a complex with iron(II) at its centre
  • The haemoglobin complex contains a multidentate ligand made up of four haem groups
    • These consist of mostly carbon and hydrogen atoms
    • Each haem group has a nitrogen atom forming a dative covalent bond to the Fe2+ ion in a square planar complex
  • There is a fifth dative bond from the protein (globin) to the Fe2+ ion
  • Oxygen atoms form a dative covalent bond with the iron(II) which enables oxygen molecules to be transported around the body in the blood

Haemoglobin

The haem molecule with iron(II) at its centre

  • Oxygen molecules are not very good ligands and bond weakly to the iron(II)
  • The weak bonds allows them to break off easily and be transported into cells

3.2-Hydrocarbons-Toxic-Effect-CO_1

 

Exam Tip

You do not need to be familiar with the structure of the haem group

Ligand Exchange in Haemoglobin

  • Carbon monoxide is toxic because it is a better ligand than oxygen and binds strongly and irreversibly to the iron(II) preventing oxygen from being carried to the cells
  • If oxygen attached to the haemoglobin (oxyhaemoglobin) is replaced by carbon monoxide (carboxyhaemoglobin), a darker red colour is produced in the haem complex
    • A sign of carbon monoxide poisoning
  • The condition anaemia occurs when a person does not have enough haemoglobin in their blood due to a loss of blood or deficiency in iron
    • Deficiency in iron can be restored by taking iron sulfate tables in the diet

 

 

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