Key concepts
Endocytosis bends plasma membrane inward to form a cargo-containing vesicle. Exocytosis fuses an intracellular vesicle with the plasma membrane and releases cargo outside. Both require proteins, membrane remodeling, and energy.
Sizes, timing, and cargo numbers are conceptually scaled. The sequence and cause-and-effect relationships are scientifically grounded.
Applications and misconceptions
Immune cells engulf microbes, cells internalize cholesterol through receptors, neurons release neurotransmitters, and endocrine cells secrete hormones.
- Endocytosis does not mean substances pass through a protein pore.
- Exocytosis does not destroy the vesicle membrane; it joins the plasma membrane.
- Receptor-mediated uptake is selective.
- Vesicles are actively sorted and transported, not simply drifting bubbles.