1.15B: Explain how substances are transported into and out of cells,
including by diffusion, osmosis and active transport

DIFFUSION: Type of passive transport (doesn't require energy inputs)
The NET MOVEMENT of particles from an area of HIGH concentration to an area of LOW concentration.
(Down the concentration gradient)
Happens in fluids- fluid particles constantly move past each other in random directions from where there's more to fewer.
OSMOSIS: Type of passive transport (doesn't require energy inputs)
The net movement of WATER molecules across a SEMI-PERMEABLE membrane from a region of HIGHER water concentration to a region of LOWER water concentration.
(Down the concentration gradient. )
Water moves both directions, randomly. More water molecules are on 1 membrane side in a certain volume - solvent molecules' net movement only stops with equal solute concentrations on both sides.
ACTIVE TRANSPORT: Form of active transport requiring energy (ATP produced in respiration).
The net movement of particles from an area of LOW concentration to an area of HIGH concentration.
(Against the concentration gradient.)
Molecules stick to transport proteins. It changes shape with energy and carries molecules across the cell membrane that are too big.
