Concept 7.5: Bulk transport across the plasma membrane occurs by exocytosis and endocytosis

Flashcards from Concept 7.5 of Pearson's Campbell Biology, Twelfth Edition.

Vesicles

Separated sections of membrane for large molecules like polysaccharides and proteins to cross the lipid bilayer

• Smaller molecules and water are transported through proteins or the layer itself instead

Exocytosis

Process where transport vesicles migrate to the membrane, fuse with it, and release their contents outside the cell

• Secretory cells like the pancreas can export products like insulin via this

Endocytosis

Process where macromolecules are taken into the cell in vescles through a pocket formed and deepened by the membrane that is eventually pinched off; includes

• Phagocytosis (cellular eating)

• Pinocytosis (cellular drinking)

• Receptor-mediated endocytosis

Phagocytosis

Form of endocytosis where a cell engulfs a particle by extending pseudopodia around it and packing it in a membranous sac called a food vacuole

• This food vacuole then fuses with a lysosome for digestion

Pinocytosis

Form of endocytosis where a cell takes up extracellular fluid via small vesicles; this is nonspecific for substance transport and any solutes are taken into the cell

• The inner side of vesicles formed from the plasma membrane are coated with coat proteins

Receptor-mediated endocytosis

Form of endocytosis where vesicle formation is triggered by a solute binding to a receptor

• Receptors bound to specific solutes from the extracellular fluid are clustered in coated pits that form coated vesicles

• Emptied receptors can be recycled into the plasma membrane by the same vesicle

• Used to take in cholesterol within particles called low-density lipoproteins (LDLs) — lack of receptors can lead to hypercholesterolemia, building up in blood vessels