3.1.8 Ions

Question 1

Where are ions found

Answer 1

Cytoplasm, tissue (interstitial) fluid & blood plasma of organisms

Question 2

Role of Hydrogen ions

Answer 2

• conc determines PH of solutions
• protein shape & function

Question 3

Role of iron ions

Answer 3

• component of Haem group in haemoglobin - binding site of o2.

Question 4

Role of sodium ions

Answer 4

1. Co-transport of glucose & amino acids in ileum and proximal convoluted tubule
2. Depolarisation & generation of action potentials in neurones

Question 5

Role of phosphate ions

Answer 5

1. Component of nucleotides
2. Component of ATP (hydrolysis of 3rd Pi to phosphorylate other compounds)

Question 6

Role of calcium ions

Answer 6

1. Initiate exocytosis of neurotransmitters at synapses
2. Bind to tropomyosin & expose myosin binding sites on actin to enable muscle contraction

Question 7

Role of potassium ions

Answer 7

• re-polarisation of neurones