Unit 2.5 - Membrane Transport

Simple Diffusion

Passive transport, down the concentration gradient, only allows small nonpolar molecules (ex. O2, CO2, N2)

Facilitated Diffusion

Passive transport, down the concentration gradient, only allows small molecules, requires transport protein such as channels and carriers (ex. water, Na+, K+, Ca-)

Active Transport

Requires energy, against concentration gradient, requires transport protein (carriers), Proton pumps, Na+ pumps, big and polar molecules

Bulk Transport

the active, energy-requiring process of moving large molecules, particles, or large quantities of substances across the cell membrane using membrane-bound vesicles

Phagocytosis

a kind of endocytosis where specialized cells (phagocytes) engulf large particles like bacteria, dead cells, and debris, protecting the body by removing threats and maintaining tissue health

Pinocytosis

a kind of endocytosis where the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

Receptor-mediated endocytosis

a kind of endocytosis where a highly selective way cells import specific large molecules (ligands) by binding them to cell surface receptors, which then cluster, bud inward in clathrin-coated pits, and form coated vesicles that deliver cargo to endosomes for sorting, recycling receptors, or degrading ligands, crucial for nutrient uptake, hormone signaling, and viral entry. 

Endocytosis

the active process where a cell engulfs substances from outside, like nutrients or pathogens, by folding its cell membrane inward to form a vesicle that buds off inside, bringing the material into the cell

Exocytosis

a process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane.

Aquaporins

a family of integral membrane proteins that form channels, allowing rapid, selective passage of water (and sometimes small solutes like glycerol) across cell membranes