3.1.8 Ions

• Hydrogen ions- H+, combines with deoxygenated haemoglobin, prevents a drop in cellular pH
• Iron ions- Fe2+, Fe3+, binds to carbon dioxide and oxygen to help oxygenation of blood
• Oxygenation of cells is aided by iron ions. Oxygen binds to the iron ions (Fe2+) in the lungs, becoming Fe3+ in the tissues and cells by gaining oxygen (and losing electrons). The iron ions lose oxygen in the tissues and cells (and gain electrons), becoming Fe2+ again.

  A) 2+

  B) 3+

  C) gain

  D) loss

  E) loss

  F) gain

  G) lungs

  H) tissue

  
• Sodium ions- Na+, involved in co-transport of charged or large molecules, determines solute concentration
• Phosphate ions- involved of synthesis of nucleic acids (DNA and RNA), synthesis of phospholipids, enzyme and protein activation
• 'Describe the roles of ions (iron, sodium, phosphate) in cells' (5 marks)

  The role of iron ions is to bind to oxygen and aid haemoglobin in oxygenating blood. The role of sodium ions is to assist co-transport- sodium is moved out of the cell by active transport, allowing glucose to move into the cell at the same time. Sodium ions also affect osmosis, as they determine the solute concentration. The role of phosphate ions is to create nucleic acids, as they are found in the sugar-phosphate backbone of the strands, and to release energy when a phosphate ion is broken off from ATP.