Final answer:
Things are brought to early endosomes largely by Endocytosis, with Receptor-mediated endocytosis being a specific process where ligand-bound receptors on a cell surface trigger the uptake of substances into the cell. Exocytosis involves the release of substances from the cell by vesicles fusing with the plasma membrane.
Step-by-step explanation:
Items are typically brought to early endosomes through a process known as Endocytosis; specific substances are often dropped off via a process called Receptor-mediated endocytosis followed by Fusion. Endocytosis involves the cell membrane enveloping extracellular material to form a vesicle, which then transports the material into the interior of the cell. There are three main forms of endocytosis:
- Phagocytosis - The cell takes in large particles in a non-selective fashion.
- Pinocytosis - The cell ingests small particles and fluid in a non-selective manner.
- Receptor-mediated endocytosis - The cell selectively engulfs substances recognized by cell-surface receptors. Upon ligand binding, receptors aggregate and the plasma membrane invaginates, forming a vesicle that internalizes the bound substances.
The exocytosis process involves the secretion of large molecules, such as proteins or glycoproteins, which are enclosed in a vesicle that fuses with the plasma membrane, releasing their contents outside the cell.