BRAINCAKECell Transport Mechanisms
Revision notes for Cell Transport Mechanisms in Edexcel Biology B (8BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- The Need for TransportEvery living cell must exchange substances with its surroundings to stay alive.
- Transport Across the Cell MembraneThe cell surface membrane is partially permeable: it lets some substances through but not others.
- Passive and Active TransportSubstances cross cell membranes either by passive transport or by active transport.
- DiffusionDiffusion is the net movement of particles (molecules or ions) from a region of higher concentration to a region of lower concentration, down a…
- Facilitated DiffusionFacilitated diffusion is the passive movement of molecules or ions down their concentration gradient through specific membrane proteins.
- Water Potential ψWater potential, symbol ψ (the Greek letter psi), is a measure of the tendency of water molecules to move out of a solution.
- OsmosisOsmosis is the net movement of water molecules across a partially permeable membrane, from a region of higher water potential to a region of lower…
- Modelling OsmosisOsmosis can be modelled in the laboratory using Visking tubing (dialysis tubing).
- Osmotic ConcentrationsSolutions can be described by comparing their water potential with that of a cell: • Isotonic: the solution has the same water potential as the…
- Osmosis in Animal CellsAnimal cells are surrounded only by a cell surface membrane.
- Water Potential in Plant CellsPlant cells behave differently from animal cells in osmosis because of their structure: • a strong, fully permeable cellulose cell wall, which…
- Osmosis in Plant CellsWhen plant cells are placed in solutions of different water potential, water moves by osmosis, but the cell wall changes what happens.
- Turgor Pressure (P)Turgor pressure (P) is the pressure exerted by the protoplast (the cell contents) pushing outwards against the cell wall.
- Osmotic Potential (π)Osmotic potential (π) is the part of water potential that is due to dissolved solutes.
- Water Potential, Turgor Pressure and Osmotic PotentialThe water potential of a plant cell has two parts: the effect of the solutes and the effect of the pressure of the cell wall.
- Active TransportActive transport is the movement of molecules or ions across a membrane from a region of lower concentration to a region of higher concentration…
- Evidence for Active TransportSeveral lines of evidence show that some substances enter cells by active transport rather than by diffusion.
- Endocytosis and ExocytosisSome molecules and particles are far too large to pass through channel or carrier proteins.
On the specification
- 4.1 Surface area to volume ratio
- 4.2 Cell transport mechanisms