Chapter 12 - Transport Across Membranes

simple diffusion

when a substance goes directly through the bilayer

gradient

differences in concentration

passive transport

no energy is needed, move from a high to low concentration

diffusion

movement that goes with the gradient

tonicity

ability of a surrounding solution to gain or lose water

facilitated diffusion

substances require a protein transporter to be able to cross the membrane

active transport

energy is required, substances move against the concentration gradient

uniporter

a protein transporter that pumps one substance across a membrane

cotransporter

a protein transporter that pumps several substances across a membrane

antiporter

a protein transporter that moves substances in opposite directions

symporter

a protein transporter that moves substances in the same direction

coupled transport

a gradient that is made by a uniporter, is used to move substances through a cotransporter

endocytosis

when materials are internalized by a cell through engulfing

phagocytosis

engulfs large solid particles

pinocytosis

engulfs a portion of something, taking in dissolved contents in bulk

receptor-mediated endocytosis

when a membrane is lined with receptors that bind to specific materials and move in bulk

clathrin-coated pits

areas where receptors are found

isotonic

movement in and out of cells is =

hypotonic

movement into the cell

hypertonic

movement out of the cell

osmoregulation

the attempt to maintain a proper water balance

selectively permeable membrane

only let in certain molecules based on their size and polarity

transcytosis

substances enter, move through, then exit a cell