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GCSE Biology · key term
A measure of how acidic or alkaline a solution is.
Used by Edexcel and OCR
Specification 1.9, 1.10 · Paper 1, Paper 2
A scale describing how acidic or alkaline a solution is.
Revise: Factors Affecting Enzyme ActivityTemperature, substrate concentration and pH affect this rate in different ways.
Specification PAG 1 · Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A way of measuring how acidic or alkaline a solution is; pH has no unit.
Revise: Magnification and General Laboratory MeasurementsTo measure pH, compare the colour of pH paper or universal indicator with its chart, or use a calibrated pH probe for a numerical reading. pH is a number without a unit.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: TechniquesTo measure pH, dip pH paper into a sample and compare its colour with the supplied chart, or use a calibrated pH meter for a numerical reading. pH has no unit. In each case, the method of reading matters as much as the choice of instrument.
A measure of how acidic or alkaline a solution is; pH has no unit.
Do not say that an enzyme is killed. At high temperatures or unsuitable pH values, it is denatured because its active site changes shape.
For temperature and pH graphs, identify the optimum at the highest rate, not simply at the middle of the range.
If asked to compare factors, remember that high temperature and unsuitable pH can change the active site, whereas increasing substrate concentration does not change the enzyme's shape.
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