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3.1.8 Inorganic ions

AQA A-level Biology 3.1.8 practice on Inorganic ions, with free MCQs, clues and worked explanations drawn from the Biological molecules section of specification 7402.

Specification route
3.1.8
Question bank
23 questions
Course stage
AS / Year 12

Sample questions

QUESTION 1 · 3.1.8 · LEVEL 2

Which inorganic ion is directly responsible for determining the pH of an environment?

  • Hydrogen ions ($H^{+}$)
  • Sodium ions ($Na^{+}$)
  • Iron ions ($Fe^{2+}$)
  • Phosphate ions ($PO_{4}^{3-}$)
Show clue

pH is the negative logarithm of the concentration of this specific ion.

Show answer and explanation

Answer: Hydrogen ions ($H^{+}$)

Students should be able to recognise the role of hydrogen ions and pH. The concentration of $H^{+}$ determines how acidic a solution is; higher concentration means lower pH.

QUESTION 2 · 3.1.8 · LEVEL 4

Which condition is necessary for the co-transport of glucose into the epithelial cells lining the ileum?

  • A concentration gradient of sodium ions ($Na^{+}$) must be maintained across the cell membrane.
  • A high concentration of hydrogen ions ($H^{+}$) inside the epithelial cell.
  • The direct hydrolysis of ATP by the co-transport protein.
  • The presence of iron ions ($Fe^{2+}$) to bind to the glucose molecules.
Show clue

The movement of glucose is coupled to the 'downhill' movement of another ion.

Show answer and explanation

Answer: A concentration gradient of sodium ions ($Na^{+}$) must be maintained across the cell membrane.

Sodium ions have a specific role in the co-transport of glucose and amino acids. $Na^{+}$ is actively pumped out of the cell, creating a gradient. $Na^{+}$ then diffuses back in through a co-transporter protein, bringing glucose with it against the glucose concentration gradient.

QUESTION 3 · 3.1.8 · LEVEL 1

What is the biological role of iron ions ($Fe^{2+}$)?

  • They act as a component of haemoglobin
  • They determine the pH of bodily fluids
  • They are components of DNA and ATP
  • They are used in the co-transport of glucose and amino acids
Show clue

These ions are essential for oxygen transport in red blood cells.

Show answer and explanation

Answer: They act as a component of haemoglobin

Iron ions are recognised as a component of haemoglobin.

QUESTION 4 · 3.1.8 · LEVEL 2

Which inorganic ion is vital for the co-transport of glucose and amino acids across cell membranes?

  • Sodium ions ($Na^{+}$)
  • Hydrogen ions ($H^{+}$)
  • Phosphate ions ($PO_{4}^{3-}$)
  • Iron ions ($Fe^{2+}$)
Show clue

This ion is actively pumped out of epithelial cells to maintain a concentration gradient in the ileum.

Show answer and explanation

Answer: Sodium ions ($Na^{+}$)

Sodium ions have a specific role in the co-transport of glucose and amino acids.

QUESTION 5 · 3.1.8 · LEVEL 1

Which components of cells specifically rely on phosphate ions ($PO_{4}^{3-}$) for their formation?

  • DNA and ATP
  • Haemoglobin and glycogen
  • Triglycerides and cellulose
  • Amino acids and simple enzymes
Show clue

Look for molecules that require a phosphodiester bond or store energy in high-energy bonds.

Show answer and explanation

Answer: DNA and ATP

Phosphate ions act as components of DNA and of ATP.

QUESTION 6 · 3.1.8 · LEVEL 1

Where in the organism do inorganic ions naturally occur in solution?

  • In the cytoplasm and body fluids of organisms
  • Exclusively within the cell-surface membrane
  • Only inside the mitochondrial matrix
  • Only attached to transport proteins
Show clue

These ions are dissolved throughout the internal environment.

Show answer and explanation

Answer: In the cytoplasm and body fluids of organisms

Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations.

QUESTION 7 · 3.1.8 · LEVEL 1

Which of the following correctly pairs an inorganic ion with its specific biological role?

  • Iron ions as a component of haemoglobin
  • Sodium ions as a component of DNA
  • Phosphate ions in the co-transport of glucose
  • Hydrogen ions as a component of ATP
Show clue

Match the metal ion to the oxygen-carrying pigment in red blood cells.

Show answer and explanation

Answer: Iron ions as a component of haemoglobin

Students should be able to recognise the role of... iron ions as a component of haemoglobin. Sodium is for co-transport , phosphate is for DNA/ATP , and hydrogen is for pH.

QUESTION 8 · 3.1.8 · LEVEL 2

What does a high concentration of hydrogen ions ($H^{+}$) in a solution indicate?

  • The solution has a low pH.
  • The solution has a high pH.
  • The solution is neutral.
  • The solution has a high concentration of sodium ions.
Show clue

The pH scale is inversely proportional to the concentration of these ions.

Show answer and explanation

Answer: The solution has a low pH.

Students should be able to recognise the role of ions in the following topics: hydrogen ions and pH. Higher $H^{+}$ concentration means greater acidity, which corresponds to a lower pH value.

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