How do endocytosis and exocytosis relate to active transport?

Endocytosis and exocytosis are forms of active transport, moving materials into and out of cells using energy.

Active transport is a process that moves ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy. This is in contrast to passive transport, which requires no energy and moves substances down their concentration gradient. Endocytosis and exocytosis are specialised types of active transport that involve the movement of larger particles or even whole cells.

Endocytosis is the process by which cells absorb molecules by engulfing them. It is used by all cells because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane. The process involves the cell membrane folding around the desired particle, forming a vesicle, which is then transported into the cell. This requires energy in the form of ATP, hence it is a form of active transport.

Exocytosis, on the other hand, is the process by which cells expel waste materials or secrete substances such as hormones or enzymes. In this process, vesicles containing the substance to be expelled are transported to the cell membrane. The vesicle membrane then fuses with the cell membrane, releasing its contents outside the cell. Like endocytosis, exocytosis also requires energy, making it another form of active transport.

In summary, both endocytosis and exocytosis are forms of active transport as they both involve the movement of substances against their concentration gradient and require energy. They are crucial for maintaining the cell's internal environment and enabling the cell to interact with its external environment.