The energy-requiring process by which large substances from the outside environment can enter a cell is called endocytosis. This process involves the engulfing of materials by the cell membrane, which then forms a vesicle that brings the substances into the cell. There are different types of endocytosis, including:
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Phagocytosis: Often referred to as "cell eating," this process involves the uptake of large particles, such as bacteria or dead cell debris.
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Pinocytosis: Known as "cell drinking," this is the process of taking in small droplets of extracellular fluid and dissolved solutes.
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Receptor-mediated endocytosis: This is a more specific form of endocytosis that targets certain substances based on their binding to specific receptors on the cell surface.
These processes require energy, usually in the form of ATP, to facilitate the deformation of the cell membrane and the transport of substances into the cell.