ions

Question 1

(a) Describe the roles of iron ions, sodium ions, and phosphate ions in cells.

Answer 1

Iron ions

1.   Haemoglobin binds/associates with oxygen

OR

Haemoglobin transports/loads oxygen;

Ignore reference to 2+ or 3+ in Fe2+ or Fe3+

Sodium ions

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;

Phosphate ions

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;

10. Hydrophilic/water soluble part of phospholipid bilayer/membrane;