Students should recognise the role of: hydrogen ions and pH; iron ions as a component of haemoglobin; sodium ions in the co-transport of glucose and amino acids; phosphate ions as components of DNA and ATP
Four key ions each do a specific job in the body. Hydrogen ions set pH, iron ions sit inside haemoglobin, sodium ions drive glucose absorption, and phosphate ions build DNA and ATP.
Formula
pH = −log₁₀[H⁺]
Real World
Oral rehydration salts (ORS) used in cholera treatment contain sodium ions precisely because Na⁺ co-transport drives glucose absorption in the gut — without Na⁺, glucose cannot enter intestinal cells even if glucose is present.
Exam Focus
Name the ion, state its location, and describe its precise function — vague answers like 'helps the body' score zero marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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