What mistakes do students make with Inorganic ions?

Assuming that ions needed only in traces are less important than abundant ones. Recognise that trace ions like iron are essential for survival. Calling inorganic ions organic, or confusing an ion with the organic molecule that contains it. State that inorganic ions do not contain carbon-hydrogen bonds. Writing charges incorrectly, for example sodium as two plus or chloride as positive. Write sodium as Na⁺ and chloride as Cl⁻.

What are the exam tips for Inorganic ions in Biology AQA A-Level?

Write the ion, not the element: iron ions, not iron, and state the charge if the question gives charges elsewhere. If a question gives a table of concentrations inside and outside a cell, comment on the direction of the difference before explaining how it is maintained.

AQA · A-Level · Biology

Course version: 7402 · Version from Sept 2016

Inorganic ions occur in solution in the cytoplasm and body fluids of…

Full specification wording

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

Inorganic ions are charged particles that contain no carbon-hydrogen bonds.

Checked against the AQA 7402 specification (opens in a new tab) on 19 September 2026.

Point 1 of 3
2 key terms

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

Inorganic ions being dissolved in the cytoplasm, blood plasma or tissue fluid.
Recognising that an ion present in very low concentration can still be essential, with a named example.
A named ion present in high concentration together with where it is found.
Ions being charged, so they cross membranes through channel or carrier proteins rather than through the bilayer.
Linking a concentration difference across a membrane to a named process such as osmosis, a resting potential or co-transport.

Common mistakes and how to put them right

Assuming that ions needed only in traces are less important than abundant ones.
Put it right: Recognise that trace ions like iron are essential for survival.
Calling inorganic ions organic, or confusing an ion with the organic molecule that contains it.
Put it right: State that inorganic ions do not contain carbon-hydrogen bonds.
Writing charges incorrectly, for example sodium as two plus or chloride as positive.
Put it right: Write sodium as Na⁺ and chloride as Cl⁻.

Exam tips

Write the ion, not the element: iron ions, not iron, and state the charge if the question gives charges elsewhere.
If a question gives a table of concentrations inside and outside a cell, comment on the direction of the difference before explaining how it is maintained.

Try the lesson

The start of the Inorganic ions: Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations. lesson, made from checked teaching notes for this specification point.

Have a go first

Which of the following is an inorganic ion found in solution in the cytoplasm of cells?

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Listen

Inorganic ions are charged particles that contain no carbon-hydrogen bonds. They dissolve because water is polar and surrounds each ion, so they occur in solution in cytoplasm, blood plasma and tissue fluid. Some are present in large amounts: sodium, potassium and chloride in plasma and cytoplasm, and hydrogencarbonate in plasma. Others act at minute concentrations: iron in haemoglobin, and copper and zinc as enzyme cofactors. Concentration is no measure of importance, since a plant starved of magnesium cannot make chlorophyll and becomes chlorotic. Note that while iodine is needed for thyroxine synthesis, it is incorporated as atoms, not free ions. A strong answer earns marks for these points. inorganic ions being dissolved in the cytoplasm, blood plasma or tissue fluid. recognising that an ion present in very low concentration can still be essential, with a named example. a named ion present in high concentration together with where it is found. ions being charged, so they cross membranes through channel or carrier proteins rather than through the bilayer. A common slip: assuming that ions needed only in traces are less important than abundant ones. Instead, recognise that trace ions like iron are essential for survival. Exam tip: Write the ion, not the element: iron ions, not iron, and state the charge if the question gives charges elsewhere.

Key words

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inorganic ions

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channel and carrier proteins

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See every definition

inorganic ions: Charged particles that contain no carbon-hydrogen bonds and occur in solution in the cytoplasm and body fluids of organisms.
channel and carrier proteins: Proteins through which charged ions cross membranes rather than through the bilayer.

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