Form basic structure. Hydrophilic heads face outwards and hydrophobic tails face inwards on either side of the bilayer. These interactions allow lipid-soluble molecules to cross but prevent water-soluble molecules from crossing.
Specific stimulus (e.g. light) → sender cell manufactures chemical to be sent → molecules (e.g. ligands) released by exocytosis and transported through bloodstream to target cell → binds to complementary receptor → effector cell stimulated
The diffusion of water across a partially permeable membrane from an area of higher water potential to an area of lower water potential. This occurs until a dynamic equilibrium is established.
The net movement of substances from a higher concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy
Active movement of substances from a low concentration to a higher concentration (against the concentration gradient) with the use of energy in the form of ATP
The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle trapping the substances inside the cell with the use of energy in the form of ATP