Lesson 3.1.8.1

3.1.8.1 Inorganic ions and their roles Quiz: AQA Biology, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.8.1, Inorganic ions and their roles: 20 multiple choice questions for the AQA Biology (7402), Unit 1: Biological molecules, written with Revision Ninja.

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The 20 questions

  1. Which ion is a component of haemoglobin, allowing it to bind oxygen?

    • Sodium ion (Na+)
    • Magnesium ion (Mg2+)
    • Calcium ion (Ca2+)
    • Iron ion (Fe2+)

  2. Which ion is co-transported with glucose and amino acids across the mammalian ileum?

    • Potassium ion
    • Calcium ion
    • Chloride ion
    • Sodium ion

  3. Which ion forms part of the backbone of DNA and of ATP?

    • Hydrogen ion
    • Phosphate ion
    • Sodium ion
    • Iron ion

  4. How is pH defined?

    • The positive logarithm to base 10 of the hydroxide ion concentration
    • The hydrogen ion concentration in mol/dm3 directly, without any conversion with no exceptions
    • The number of hydrogen ions per cubic centimetre of solution
    • The negative logarithm to base 10 of the hydrogen ion concentration in mol/dm3

  5. What role do hydrogen ions have in biological systems?

    • They form the phosphodiester bonds that join the nucleotides together in a DNA strand
    • They determine pH, which affects the ionisation of R groups and the activity of enzymes
    • They are co-transported with glucose into the cells lining the ileum by a specific carrier protein
    • They are the main component of haemoglobin, where they bind oxygen directly within the red blood cell

  6. What does an iron ion in haemoglobin bind?

    • Oxygen
    • Glucose
    • Carbon dioxide only
    • Sodium ions

  7. Which ion is found at very low concentration in some cells but has an essential specific role?

    • Iron ion, which is essential for oxygen transport in haemoglobin
    • Hydrogen ion, which is found only in the nucleus as a component of DNA
    • Phosphate ion, which is found only in the cell membrane as a lipid
    • Sodium ion, which is found at high concentrations and forms DNA

  8. A solution has a hydrogen ion concentration of 1 x 10^-3 mol/dm3. What is its pH?

    • 3
    • 10
    • 1
    • 11

  9. How many times greater is the hydrogen ion concentration at pH 5 than at pH 7?

    • 100 times
    • 2 times
    • 1000 times
    • 10 times

  10. What is the hydrogen ion concentration of a solution at pH 9?

    • 1 x 10^-5 mol/dm3
    • 1 x 10^-9 mol/dm3
    • 1 x 10^9 mol/dm3
    • 9 mol/dm3

  11. How does sodium co-transport help the cells lining the ileum absorb glucose?

    • Sodium moves into the cell and blocks glucose from leaving it, so that the glucose stays trapped inside
    • Glucose moves down its own gradient and carries sodium into the cell with it through the carrier
    • Sodium and glucose both move out of the cell together through the same channel in the membrane
    • Sodium moves down its concentration gradient into the cell, carrying glucose against its own gradient

  12. A drug stops the sodium-potassium pump, which keeps the sodium gradient across the ileum cell membrane. What is the likely effect on glucose absorption?

    • Glucose absorption falls, because the sodium gradient that drives co-transport is reduced
    • Glucose absorption is unchanged, because glucose enters the cell by simple diffusion alone
    • Glucose absorption stops entirely, because glucose is converted into haemoglobin
    • Glucose absorption rises, because the drug increases the diffusion of glucose

  13. A patient has a shortage of iron ions. Which effect on the blood is most likely?

    • The blood glucose rises because iron stops sodium co-transport
    • More haemoglobin is made, so more oxygen is transported in the blood with no exceptions
    • Less haemoglobin is made, so less oxygen can be transported in the blood
    • The blood pH falls because iron ions produce hydrogen ions

  14. Which inorganic ion is hydrolysed from ATP to provide a phosphate group for phosphorylation?

    • Sodium ion, released when ATP is hydrolysed
    • Inorganic phosphate (Pi), released when ATP is hydrolysed
    • Hydrogen ion, released when ATP is resynthesised
    • Iron ion, released from haemoglobin during ATP hydrolysis

  15. Explain why a small change in hydrogen ion concentration causes a large change in pH.

    • pH is a linear scale, so a small change in hydrogen ions gives only a small pH change
    • pH depends only on the number of water molecules, which changes sharply with hydrogen ions with no exceptions
    • Hydrogen ions are present in very large amounts, so small changes are rapidly buffered
    • pH is a logarithmic scale, so each unit represents a tenfold change in hydrogen ion concentration

  16. Explain why sodium-glucose co-transport depends indirectly on ATP.

    • ATP hydrolysis drives active transport that pumps sodium out of the cell, maintaining the gradient used for co-transport
    • ATP is converted into sodium ions, which then carry glucose into the cell through the cell membrane
    • ATP is directly used to move glucose into the cell through a channel protein in the membrane of the cell
    • ATP forms the peptide bond that holds the sodium ion to the glucose molecule during co-transport across the membrane in every case

  17. Explain why the iron ion in haemoglobin must remain in the Fe2+ form to carry oxygen.

    • Fe2+ is always covalently bonded to the haem group, so it cannot release oxygen
    • Fe2+ binds oxygen reversibly, whereas the oxidised Fe3+ form does not bind oxygen in the same way
    • Fe2+ is positively charged, which repels oxygen molecules from haemoglobin
    • Fe2+ is a non-metal that forms peptide bonds with oxygen

  18. A student claims that all inorganic ions are present in cells at the same concentration. Which evaluation is correct?

    • Correct, because the cell maintains each ion at a fixed equal concentration
    • Incorrect, because ions are never found in the cytoplasm of cells
    • Correct, because ions only differ in concentration in the blood and not in cells
    • Incorrect, because ions occur at very different concentrations, with some high and others very low

  19. Why is the phosphate ion a suitable group for phosphorylation of other compounds?

    • Phosphate forms a glycosidic bond that stabilises the compound
    • Phosphate removes an electron from the compound, making it unreactive
    • Phosphate is non-polar, so it prevents the compound from reacting with water with no exceptions
    • Transferring a phosphate group often makes the recipient compound more reactive

  20. Explain why hydrogen ions can affect enzymes even though they are present at very low concentrations.

    • Hydrogen ions directly break the peptide bonds in the backbone of the enzyme molecule when present
    • Hydrogen ions are present in such a low concentration that they can only bind to the substrate molecules
    • Changes in hydrogen ion concentration alter the ionisation of R groups in the active site, changing its shape and charge
    • Hydrogen ions are converted into sodium ions, which then block the active site of the enzyme completely

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