3.1.8 Inorganic ions

Question 1

What is the role of hydrogen ions in pH?

Answer 1

Hydrogen ions (H+) determine pH by their concentration higher H+ concentration means lower pH more acidic lower H+ concentration means higher pH more alkaline.

Question 2

What is the role of iron ions in haemoglobin?

Answer 2

Iron ions (Fe2+) are a component of haemoglobin in red blood cells each Fe2+ ion binds to one oxygen molecule forming oxyhaemoglobin oxygen is released when Fe2+ becomes Fe3+.

Question 3

How do sodium ions help in the co-transport of glucose and amino acids?

Answer 3

Sodium ions (Na+) are actively transported out of epithelial cells in the small intestine creating a sodium concentration gradient sodium diffuses back into the cell via a co-transporter protein bringing glucose or amino acids with it by facilitated diffusion.

Question 4

What is the role of phosphate ions in DNA and ATP?

Answer 4

Phosphate ions (PO4 3-) are a component of nucleotides forming the sugar-phosphate backbone of DNA and RNA they also store energy in ATP molecules where hydrolysis of the phosphate bond releases energy for cellular processes.

Question 5

Describe the roles of iron ions in cells.

Answer 5

1. Haemoglobin binds/associates with oxygen
   OR
   Haemoglobin transports/loads oxygen;

Question 6

Describe the roles of sodium ions in cells.

Answer 6

2. Co-transport of glucose/amino acids (into cells);
3. (Because) sodium moved out by active transport/Na – K pump;
4. Creates a sodium concentration/diffusion gradient;
5. Affects osmosis/water potential

Question 7

Describe the roles of Phosphate ions in cells.

Answer 7

6. Affects osmosis/water potential;
   Accept 5. OR 6. – not both
7. Joins nucleotides/in phosphodiester bond/in backbone of
   DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
   Reject ‘energy produced’
9. Phosphorylates other compounds (usually) making them more
   reactive;