What is Endocytosis?

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Endocytosis is a cellular process by which cells actively take in substances from their external environment by engulfing them with their plasma membrane. This process results in the formation of a vesicle—a small, membrane-bound sac—that contains the ingested material and transports it into the cell.How Does Endocytosis Work?The cell membrane invaginates (folds inward) around the material to be internalized.The membrane then pinches off, forming a vesicle that encloses the material inside the cell.The vesicle can then fuse with other organelles, such as lysosomes, where its contents may be digested or processed.Endocytosis is a form of active transport, meaning it requires energy because it moves substances against their concentration gradient.Types of EndocytosisTypeDescriptionExample UsePhagocytosis ("cell eating")Engulfment of large particles, such as debris or microorganisms, by forming pseudopodiaUsed by immune cells like macrophagesPinocytosis ("cell drinking")Uptake of extracellular fluid and dissolved small moleculesGeneral nutrient and fluid absorptionReceptor-mediated endocytosisHighly specific uptake of molecules after binding to cell surface receptors; often clathrin-mediatedUptake of hormones, nutrients, and virusesEndocytosis Functions and ImportanceNutrient uptake: Cells absorb essential nutrients and fluids.Pathogen defense: Immune cells engulf and destroy pathogens.Cell signaling regulation: Cells internalize receptors to modulate responses to external signals.Membrane turnover: Helps regulate and recycle components of the plasma membrane.

What is Endocytosis?

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How Does Endocytosis Work?

Types of Endocytosis

Endocytosis Functions and Importance

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Type	Description	Example Use
Phagocytosis ("cell eating")	Engulfment of large particles, such as debris or microorganisms, by forming pseudopodia	Used by immune cells like macrophages
Pinocytosis ("cell drinking")	Uptake of extracellular fluid and dissolved small molecules	General nutrient and fluid absorption
Receptor-mediated endocytosis	Highly specific uptake of molecules after binding to cell surface receptors; often clathrin-mediated	Uptake of hormones, nutrients, and viruses