Scientists Say: Endocytosis

This is what happens when a cell needs to take in something big

endocytosis diagram

When a cell membrane folds around a substance outside of the cell, this is called endocytosis. 

Mariana Ruiz Villarreal LadyofHats/Wikimedia Commons

Endocytosis (noun, “EN-doh-sy-TOH-sis”)

This is a process in which a cell captures something outside of itself by engulfing the substance within part of its outer membrane. That protective membrane surrounds the cell. During endocytosis, that membrane reaches out and also surrounds — and encloses — the substance it wants to take in. This creates what amounts to a bag. The membrane can then pinch off the outer top of this bag, now fully enclosing its contents.

Endocytosis can be divided into two types. Phagocytosis (FAG-oh-sy-TOH-sis) or cellular eating — describes engulfing solid substances, such as other cells. Pinocytosis (PEE-noh-sy-TOH-sis) — or cellular drinking — refers to when a cell creates a channel to let some liquid flow in. Pinching off that channel traps liquid inside.

In a sentence

Some immune cells gobble up nasty invaders by endocytosis — but vaping liquids can prevent these cellular cops from doing their jobs.

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Power Words

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cell   The smallest structural and functional unit of an organism. Typically too small to see with the naked eye, it consists of watery fluid surrounded by a membrane or wall. Animals are made of anywhere from thousands to trillions of cells, depending on their size. Some organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

cell membrane    Separates the inside of a cell from the outside of it. Some particles are permitted to pass through the membrane.

endocytosis     The process in which a cell captures and takes in something that was outside itself by using its outer wall, or membrane, to engulf the material.

phagocytosis    Sometimes called cellular eating, this is when a cell takes in solid materials using the process known as endocytosis.

pinocytosis     Also called “cellular drinking,” this is when a cell folds its outer membrane inward to make a straw-like channel through which some liquid can enter. When the channel pinches off, the liquid become trapped inside the cell.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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