2.3—Core Practical 3 - membrane permeability

A permeability experiment uses a measurable proxy for material crossing a membrane, such as pigment leaking from beetroot cells. The proxy is not the membrane itself; it is evidence that membrane integrity or permeability changed.

Cut equal tissue pieces, rinse away surface pigment, place them in controlled volumes at different temperatures or treatments, and measure colour intensity with a colorimeter after the same time.

A colorimeter converts absorbance into comparable data, while repeats and a blank reduce random and background effects. Control tissue size, surface area, solvent volume and time so the tested variable is isolated.

If hotter water causes greater pigment absorbance, infer that membrane permeability increased under that condition. Do not infer a precise molecular pore size from colour alone.

The conclusion concerns the chosen tissue, treatment and proxy. It does not automatically generalise to every membrane or prove that all cell contents escaped.