19 terms

Active Membrane transport processes description

P80 Active transport, vesicular transport
2 types of active transport
active transport and vesicular transport
Primary active transport
Transport of substance against a concentration (or electrochemical) gradient; across the plasma membrane by a solute pump; directly uses energy of ATP hydrolysis
Second active transport
cotransport (coupled transport) of two solutes across the membrane; energy is supplied by the ion gradient created by a primary active solute pump (indirectly); symporters move the transported substances in the same direction; antiporters move transported substances in opposite directions across the membrance.
3 types of vesicular transport
exocytosis, endocytosis, intracellular vesicular trafficking
exocytosis vesicular transport
moving substance out of the cell; Secretion or ejection of sustances from a cell; the substance is enclosed in a membranous vesicle; which fuses with the plasma membrane and reptures; releasing the substance to the exterior
2 ways of endocytosis
Via clathrin-coated vesicles, and Via caveolin-coated vesicles (caveolae)
Cell eating: A large external particle (protein, bacteria, dead cell debris) is surrounded by a "seizing foot" and becomes enclosed in a vesicle (phagosome)
fluid-phase endocytosis, Plasma membrane sinks beneath an external fluid droplet containing small solutes; membrane edges fuse, forming a fluid-filled vesicle; clathrin-coated vesicles formed.
Receptor-medicated endocytosis
Selective endocytosis and transcytosis; external substance binds to membrane receptors, and clathrin-coated pits are formed
Via caveolin-coated vesicles
Selective endocytosis (and trascytosis); external substance binds to membrane receptors (often associated with lipid rafts); caveolin-coated vesicles formed
Via coatomer-coated vesicles
vesicles coated with coatomer proteins pinch off from organelles and travel to other organelles to deliver their cargo
Primary active transport examples
Ions such as: Na+, K+, H+, Ca2+, and other others.
Secondary active transport examples
Movement of polar or charged sulutes, e.g., amino acids (into cell by symporters); Ca2+, H+ (out of cells via antiporters)
Exocytosis vesicular transport examples
Secrection of neurotransmitters, hormones, mucus, etc.; ejection of cell wastes
Phagocytosis examples
In the human body, occurs primarily in protective phagocytes (some white blood cells and macrophages)
Pinocytosis examples
Occurs in most cells; important for taking in dissolved soultes by absorptive cells of the kidney and intestine.
Receptor-mediated endocytosis examples
Means of intake of some hormones, cholesterol, iron, and most macromolecules.
Via caveolin-coated vesicles examples
Roles not fully know; proposed roles include choldsterol regulation and trafficking; platforms for signal transduction
Intracellular vesicular trafficking examples
Accounts for nearly all intracellular trafficking of molecules.