mitochondrion

[mahy-tuh-kon-dree-uhn]
noun, plural mitochondria [mahy-tuh-kon-dree-uh] . Cell Biology.
an organelle in the cytoplasm of cells that functions in energy production.

Origin:
1900–05; < Greek míto(s) thread + chóndrion small grain, equivalent to chóndr(os) grain, corn + -ion diminutive suffix

mitochondrial, adjective
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World English Dictionary
mitochondrion (ˌmaɪtəʊˈkɒndrɪən)
 
n , pl -dria
Also called: chondriosome a small spherical or rodlike body, bounded by a double membrane, in the cytoplasm of most cells: contains enzymes responsible for energy production
 
[C19: New Latin, from Greek mitos thread + khondrion small grain]
 
mito'chondrial
 
adj

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Etymonline
Word Origin & History

mitochondria
1901, from Ger., coined 1898 by microbiologist Carl Benda (1857-1933), from Gk. mitos "thread" (see mitre) + khondrion "little granule," dim. of khondros "granule, lump of salt."

mitochondrion
singular of mitochondria.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

mitochondrion mi·to·chon·dri·on (mī'tə-kŏn'drē-ən)
n. pl. mi·to·chon·dri·a (-drē-ə)
A spherical or elongated organelle in the cytoplasm of nearly all eukaryotic cells, containing genetic material and many enzymes important for cell metabolism, including those responsible for the conversion of food to usable energy. It consists of two membranes: an outer smooth membrane and an inner membrane arranged to form cristae.


mi'to·chon'dri·al (-drē-əl) adj.
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American Heritage
Science Dictionary
mitochondrion  [%PREMIUM_LINK%]     (mī'tə-kŏn'drē-ən)  Pronunciation Key 
Plural mitochondria
A structure in the cytoplasm of all cells except bacteria in which food molecules (sugars, fatty acids, and amino acids) are broken down in the presence of oxygen and converted to energy in the form of ATP. Mitochondria have an inner and outer membrane. The inner membrane has many twists and folds (called cristae), which increase the surface area available to proteins and their associative reactions. The inner membrane encloses a liquid containing DNA, RNA, small ribosomes, and solutes. The DNA in mitochondria is genetically distinct from that in the cell nucleus, and mitochondria can manufacture some of their own proteins independent of the rest of the cell. Each cell can contain thousands of mitochondria, which move about producing ATP in response to the cell's need for chemical energy. It is thought that mitochondria originated as separate, single-celled organisms that became so symbiotic with their hosts as to be indispensible. Mitochondrial DNA is thus considered a remnant of a past existence as a separate organism. See more at cell, cellular respiration.

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American Heritage
Cultural Dictionary
mitochondrion [(meye-tuh-kon-dree-uhn)]

The cell organelle where much of cellular respiration takes place; the “power plant” of the cell.

Note: Mitochondria probably entered eukaryotes by an act of endosymbiosis, in which one simple cell was absorbed by another.
Note: Mitochondria contain their own DNA. It is by tracing the mitochondrial DNA, which individuals inherit only from their mothers, that genetic linkeages are often traced. (See mitochondrial Eve.)

A cutaway view.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
Red blood cells lack mitochondria, but other cells may contain anywhere from 50
  to 5000 of them, depending on their jobs.
Every animal cell contains structures called mitochondria that produce the
  cell's fuel.
At issue are little power factories inside cells, called mitochondria.
Researchers are now zeroing in on a promising missing link: mitochondria, the
  cell components responsible for energy regulation.
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