Explain the importance of inorganic ions in the synthesis of proteins and in the generation of electrochemical gradients across cell membranes.

AQA A-Level Biology (7402) — 3.1.8 Inorganic Ions · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Nitrate ions are required for the synthesis of amino acids, which are the monomers that are joined together to form proteins.
Sodium (or potassium) ions are involved in generating an electrochemical gradient across cell membranes. This gradient creates a potential difference (voltage) across the membrane, which is important for processes such as nerve impulse transmission, active transport and ATP synthesis.

Examiner tips

Use the exact terminology (nitrate, amino acids, monomers, proteins, sodium, potassium, electrochemical gradient, potential difference, nerve impulse, active transport, ATP synthesis).
Show the logical link: nitrate → amino acids → proteins; ions → gradient → potential difference → cellular processes.
Keep the answer concise and directly address each point.

Common mistakes

Confusing nitrate with other nitrogen sources; not linking ions to amino acid synthesis.
Using vague terms like "ions" without specifying sodium or potassium.

Mark scheme (5 marks)

Nitrate ions are needed for the synthesis of amino acids / proteins
Amino acids are the monomers / building blocks that are joined to form proteins
Sodium ions (or potassium ions) are involved in generating an electrochemical gradient across cell membranes
The electrochemical gradient results in a potential difference / voltage across the membrane
This electrochemical gradient / potential difference is important for processes such as nerve impulse transmission / active transport / ATP synthesis

Key terms in this question

inorganic ions · electrochemical gradient