B5. Inorganic Ions

Question 1

Iron ions in haemoglobin

What is haemoglobin and where is it found?
Where are the iron ions found?
What do iron ions do?

Answer 1

Haemoglobin is a large protein that carries oxygen around the body, in the red blood cells. It’s made up of four different polypeptide chains, each with an iron ion (Fe²+) in the centre. It’s the Fe²+ that actually binds to the oxygen in haemoglobin-so it’s a pretty key component. When oxygen is bound, the Fe²+ ion temporarily becomes an Fe3+ ion, until oxygen is released.

Question 2

Hydrogen ions

What does the concentration of this mean?

Answer 2

pH is calculated based on the concentration of hydrogen ions (H) in the environment. The more H present, the lower the pH (and the more acidic the environment). Enzyme-controlled reactions are all affected by pH.

Question 3

Sodium ions

What are they used for?

Answer 3

Glucose and amino acids need a bit of help crossing cell membranes. A molecule of glucose or an amino acid can be transported into a cell (across the cell-surface membrane) alongside sodium ions (Na). This is known as co-transport

Question 4

Phosphate ions

What 3 molecules is it in?

What is its job in all 3?

Answer 4

When a phosphate ion (PO) is attached to another molecule, it’s known as a phosphate group. DNA, RNA and ATP all contain phosphate groups. It’s the bonds between phosphate groups that store energy in ATP. The phosphate groups in DNA and RNA allow nucleotides to join up to form the polynucleotides