Final answer:
Large molecules exit cells through exocytosis, an active transport mechanism that uses energy to move materials against a concentration gradient.
Step-by-step explanation:
Large molecules exit cells via a mechanism of bulk transport known as exocytosis. This process involves the transport of materials inside vesicles that fuse with the cell's plasma membrane, releasing their contents to the exterior. Exocytosis is a type of active transport because it requires energy, usually from ATP, to carry out the movement of materials against the concentration gradient.
In contrast to exocytosis, endocytosis is the process by which cells internalize particles and large molecules. Various forms of endocytosis exist, such as phagocytosis for large particles, pinocytosis for fluid-phase uptake, and receptor-mediated endocytosis, which is highly selective for specific substances recognized by cell surface receptors. Both exocytosis and endocytosis are crucial for maintaining cellular functions and homeostasis.