Final answer:
Endocytosis is the process of a cell taking in substances from outside by engulfing them with the cell membrane. Exocytosis is the process of a cell releasing substances to the outside by fusion of vesicles with the plasma membrane.
Step-by-step explanation:
Endocytosis is the process by which a cell takes in substances or particles from outside the cell by engulfing them with the cell membrane. There are three main types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis. Phagocytosis is the engulfment of large particles, such as bacteria, while pinocytosis is the engulfment of fluid or small particles. Receptor-mediated endocytosis is when specific substances are recognized by cell-surface receptors and taken into the cell.
In contrast, exocytosis is the process by which a cell releases substances to the outside of the cell. This occurs through the fusion of vesicles, which contain the substances, with the plasma membrane. Exocytosis is used by cells to export various molecules, including proteins, hormones, and digestive enzymes.