define endocythosis
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Answer:
Endocytosis is the process of actively transporting molecules into the cell by engulfing it with its membrane. Endocytosis and exocytosis are used by all cells to transport molecules that cannot pass through the membrane passively. Exocytosis provides the opposite function and pushes molecules out of the cell. Like all systems in the human body, the need for homeostasis enables an equal flow of molecules in and out of the cell. This means the amount of molecules entering the cell by endocytosis is equal to the amount of molecules exiting the cell via exocytosis. The two processes combined ensure there is a balance of nutrients and waste for regular cell life and function.
Necessary components in the endocytic pathway are early endosomes, late endosomes, and lysosomes. Early endosomes are responsible for receiving vesicles on the cell surface. They sort the received molecules into the other components in the pathway through trans vesicular compartments such as endosomal carrier vesicles or multivesicular bodies. Late endosomes then receive the molecules from early endosomes. They begin the degradation of the molecules and can also receive molecules from the trans-Golgi network or from phagosomes. Late endosomes then deliver the molecules to lysosomes. Lysosomes contain enzymes that break down carbohydrates, proteins, fats, and other cellular waste products into smaller, simpler components. These components are then delivered back to the cytoplasm to be used as building materials throughout the cell.