the plasma membrane is selective about what passes through it, it allows nutrients to enter the cell but keeps out undesirable substance. by the same toke, valuable cell proteins and other substances are kept within the cell, and excreta or wastes pass to the exterior.

transport through the plasma membrane based on concentration or pressure differences driving the movement. Two important processes: diffusion and filtration.

transport through the plasma membrane by the cell providing energy (ATP) to power the transport process. two types: active transport, and vesicular transport

passive molecular movement from an area of higher concentration to an area of lower concentration

regional differences in the concentration of a particular substance

the unassisted diffusion of solutes through a selectively permeable membrane

the passive movement of a substance across a plasma membrane by means of a protein carrier

the flow of water across a selectively permeable membrane from one solution to another solution that contains a higher solute concentration

cells retain their normal size and shape in isotonic solutions (same solute/water concentration as inside cells; no net osmosis).

cells lose water by osmosis and shrink in a hypertonic solution (contains a higher concentration of solutes than are present inside the cells)

cells take on water by osmosis until they become bloated and burst (lyse) in a hypotonic solution (contains a lower concentration of solutes than are present in cells)

cellular shrinkage due to an osmotic movement of water out of the cytoplasm

a passive process in which water and solutes are forced through a membrane by hydrostatic (fluid) pressure. filtration in not selective

the ATP-dependent absorption or secretion of solutes across a plasma membrane

fluids containing large particles and macromolecules are transported across cellular membranes inside membranous sacs called vesicles. vesicular transport moves substances into the cell (endocytosis) and out of the cell (exocytosis).

the movement of relatively large volumes of extracellular material into the cytoplasm via the formation of a membranous vessel at the cell surface, 3 types phagocytosis, pinocytosis, and receptor-mediated endocytosis

the cell engulfs some relatively large or solid material such as a clump of bacteria, cell debris, or inanimate particles. When a particle binds to receptors on the cell's surface, cytoplasmic extensions called pseudopods form and flow around the particle. this produces an endocytotic vesicle called a phagosome.

also called fluid-phase endocytosis, the cell "gulps" a drop of extracellular fluid containing dissolved molecules.

the main mechanism for specific endocytosis of most macromolecules, the receptors for this process are plasma membrane proteins that bind only certain substances

a vesicular transport process that ejects substances from the cell into the extracellular fluid. the substance to be removed from the cell is first enclosed in a protein-coated vesicle called a secretory vesicle.