Egestion

How this is marked

Examiners deliberately test egestion against excretion, and most lost marks come from mixing them up. The paying point is that egested material is undigested food that was never absorbed into cells, so it was never part of metabolism; excreted material is the waste of chemical reactions inside cells. Never call faeces an excretory product. This distinction appears in Paper 4 nutrition questions.

In an exam answer

Distinguishing the two terms: 'Faeces are removed by egestion because they are undigested food that was never absorbed, whereas urea is removed by excretion because it is a waste product of metabolism made in cells.'

Full topic guide: Human nutrition