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GCSE Biology · key term
The quantity of a dissolved substance in a given volume of solution.
Used by Edexcel and OCR
Specification 1.9, 1.15 · Paper 1, Paper 2
Revise: Factors Affecting Enzyme ActivityTemperature, substrate concentration and pH affect this rate in different ways.
The number of particles of a substance in a given volume.
On a substrate-concentration graph, explain the plateau by stating that all enzyme active sites are occupied. Do not claim that the substrate has run out.
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.
State the direction relative to the concentration gradient: diffusion moves particles down it, whereas active transport moves substances against it.
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Specification B1.2g, B3.3g · Paper 1 (Foundation), Paper 3 (Higher)
A measure of the quantity of a dissolved substance in a given volume of solution.
Revise: Factors Affecting the Rate of Enzyme ReactionsAt a low substrate concentration, relatively few substrate molecules are available. Increasing the concentration puts more substrate particles into the same volume, producing more frequent collisions with active sites. More enzyme–substrate complexes form each second, so the rate increases.
The amount of a dissolved substance present in a given volume of solution.