Membrane Transport Process
Membrane Transport Process
Process
Energy Source
Description
Examples
Passive processes
Simple diffusion Kinetic energy Kinetic energy Net movement of particles (ions. molecules. etc.) from an area of their higher concentration to an area of their lower concentration. that is. along their concentration gradient Movement of fats, oxygen, carbon dioxide through the lipid portion of the membrane, and ions through protein channels under certain conditions
Osmosis Kinetic energy Simple diffusion of water through a selectively permeable membrane Movement of water into and out of cells via membrane pores
Facilitated diffusion Kinetic energy Same as simple diffusion. but the diffusing substance is attached to a lipid-soluble membrane carrier protein Movement of glucose into cells
Filtration Hydrostatic pressure Movement of water and solutes through a semipermeable membrane from a region of higher hydrostatic pressure to a region of lower hydrostatic pressure that is along a pressure gradient Movement of water, nutrients, and gases through a capillary wall; formation of kidney filtrate
Active processes
Active transport (solute pumping) ATP (cellular energy) Movement of a substance through a membrane against a concentration (or electrochemical) gradient: requires a membrane carrier protein Movement of amino acids and most ions across the membrane Bulk transport
Exocytosis ATP Secretion or ejection of sub- stances from a cell: the sub- stance is enclosed in a membranous vesicle. which fuses with the plasma membrane and ruptures. Releasing the substance to the exterior Secretion of neurotransmitters, hormones, mucus, etc; ejection of cell wastes
Phagocytosis (endocytosis) ATP 'Cell eating" A large external particle (proteins. bacteria. dead cell debris) is surrounded by a "seizing foot" and becomes enclosed in a plasma membrane sac In the human body, occurs primarily in protective phagocytes (some white blood cells, macrophages)
Pinocytosis
Process
Energy Source
Description
Examples
Passive processes
Simple diffusion Kinetic energy Kinetic energy Net movement of particles (ions. molecules. etc.) from an area of their higher concentration to an area of their lower concentration. that is. along their concentration gradient Movement of fats, oxygen, carbon dioxide through the lipid portion of the membrane, and ions through protein channels under certain conditions
Osmosis Kinetic energy Simple diffusion of water through a selectively permeable membrane Movement of water into and out of cells via membrane pores
Facilitated diffusion Kinetic energy Same as simple diffusion. but the diffusing substance is attached to a lipid-soluble membrane carrier protein Movement of glucose into cells
Filtration Hydrostatic pressure Movement of water and solutes through a semipermeable membrane from a region of higher hydrostatic pressure to a region of lower hydrostatic pressure that is along a pressure gradient Movement of water, nutrients, and gases through a capillary wall; formation of kidney filtrate
Active processes
Active transport (solute pumping) ATP (cellular energy) Movement of a substance through a membrane against a concentration (or electrochemical) gradient: requires a membrane carrier protein Movement of amino acids and most ions across the membrane Bulk transport
Exocytosis ATP Secretion or ejection of sub- stances from a cell: the sub- stance is enclosed in a membranous vesicle. which fuses with the plasma membrane and ruptures. Releasing the substance to the exterior Secretion of neurotransmitters, hormones, mucus, etc; ejection of cell wastes
Phagocytosis (endocytosis) ATP 'Cell eating" A large external particle (proteins. bacteria. dead cell debris) is surrounded by a "seizing foot" and becomes enclosed in a plasma membrane sac In the human body, occurs primarily in protective phagocytes (some white blood cells, macrophages)
Pinocytosis