Mechanisms for moving materials through cell membranes
Process How it works Energy source Example
PHYSICAL passive transport
A. diffusion net movement of random movement of oxygen
particles from region molecular into cells or into lungs
of [high] to [low] motion
B. facilitated membrane proteins random import of glucose
diffusion accelerate movement molecular
of particles down movement
concentration gradient
C. osmosis diffusion of water random red blood cells burst when
molecular placed in distilled water
motion
PHYSIOLOGICAL active transport
A. electrogenic pumps membrane proteins cellular energy Na+/K+ ATPase
pump ions against (ATP) in animal cells;
concentration gradient proton pumps in
plant cells
B. proton pumps protons pumped electron generation of
against concentration transport proton motive
gradient chain force in Mt & Cp
C. bulk movement particles in vesicles cellular energy secretion of mucus
or vacuoles moving (ATP) (exocytosis)
across cell membrane
white blood cells ingest bacteria
(phagocytosis)
cell imports necessary solutes in
fluid droplets (pinocytosis)
vesicle formed when ligand binds
to receptor (cholesterol movement)
(receptor-mediated endocytosis)