mixed composition of phospholipids, glycolipids, sterols and proteins.
transport proteins
either passively let specific solutes diffuse through a membrane spanning channel in their interior or actively pump them through.
receptor proteins:
bind extracellular substances.
recognition proteins:
that are unique identity tags for each species.
adhesion proteins:
help cells of the same type locate each other and remain in the proper tissues.
communication proteins:
form channnel that match up across the plasma membranes of two cells.
concentration gradient:
is a difference in the number per unit volume of molecules (or ions) of a substance between two adjoining regions.
diffusion:
is the name for the net movement of like molecules or ions down a concentration gradient.
electric gradient:
is a simply difference in electric charge between adjoining regions.
pressure gradient:
is the difference in pressure exerted per unit volume between two adjoining regions.
passive transport:
a concentration gradient, electric gradient, or both drive diffusion of a substances across a cell membrane.
active transport:
energy-driven protein motors help a particular kind of solute cross a cell membrane against its concentration gradient.
osmosis:
is the diffusion of water across a selectively permeable membrane.
hypotonic solution:
is the one with fewer solutes.
hypertonic solution:
one having more solutes.
isotonic solutions:
show no net osmotic movement.
hydrostatic pressure:
against the wall or membrane that contains it.
osmotic pressure:
any fluid is one measure of the tendency of water to follow its water concentration gradient and move into that fluid.
endocytosis:
A small patch of plasma membrane, ballons inwards and pinches off inside of the cytoplasm.
exocytosis:
a vesicle moves to the cell surface, and then the protein-studded lipid bilayer of its membrane.
