Organelle
Say it: or-guh-NEL
An organelle is a specialized structure inside a cell, usually wrapped in its own membrane, that carries out a particular job for the cell.
Also: organelles
Definition
What is an organelle?
An organelle is a distinct structure within a cell that performs one or more specific tasks. The name means little organ, because organelles divide up the work of a cell much as organs divide up the work of a body. Familiar examples include the nucleus, which stores the cell's DNA, mitochondria, which release energy from food, and chloroplasts, which capture light energy in plants and algae.
Most organelles are enclosed by their own membrane, which lets each one keep a separate internal environment. Lysosomes, for instance, stay acidic so that their digestive enzymes can work, while mitochondria gather the enzymes of cellular respiration in one place. Keeping these contents apart allows chemical reactions that would interfere with one another to run side by side in the same cell.
Membrane-bound organelles are a defining feature of eukaryotic cells; prokaryotes such as bacteria lack them. Textbooks differ on whether structures without a membrane, such as ribosomes, should also be called organelles, so the word is used a little more broadly in some courses than in others.
Word parts
Where does the word “organelle” come from?
- organ-
- organ, toolLatin organum
- -elle
- small (a diminutive ending)New Latin -ella, via French
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Related
Terms that go with it
- NucleusThe nucleus is the membrane-bound organelle that holds a eukaryotic cell's chromosomes and controls which of its genes are used and when.
- MitochondrionA mitochondrion is a double-membraned organelle that makes most of a eukaryotic cell's ATP by breaking down fuel molecules with oxygen.
- ChloroplastA chloroplast is the green organelle in plant and algal cells that captures light energy and uses it to make sugars by photosynthesis.
- LysosomeA lysosome is a membrane-bound organelle filled with acidic digestive enzymes that break down worn-out cell parts, food particles and microbes.
- EukaryoteA eukaryote is an organism whose cells keep their DNA inside a membrane-bound nucleus and contain other membrane-bound organelles.
- Golgi apparatusThe Golgi apparatus is a stack of flattened membrane sacs that modifies, sorts and packages proteins and lipids sent from the endoplasmic reticulum.
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