Intro to
Chapter 5
Mechanisms of
membrane transport
Diffusion
 Follows concentration gradient
 No energy required
Osmosis
 Water diffuses, following
concentration gradient
 No energy required
Mechanisms of
membrane transport
Facilitated Diffusion
 Follows concentration gradient
 Assisted by channel proteins
 No energy required
Active Transport
 Moves AGAINST the concentration gradient
 Assisted by channel or carrier proteins
 Energy input is required
Mechanisms of
membrane transport
Endocytosis
 Membrane engulfs a substance and draws it
into the cell in the membrane-bounded
vesicle
Exocytosis
 Membrane-bounded vesicle fuses with cell
membrane, releasing the cell’s contents
outside of the cell