In
eukaryotes,
mitochondria are responsible for the production of
ATP. ATP is used as the
currency of the cell, or so says my
molecular biology professor Dr.
Niels Bohls; if you want to do anything as a cell, you must have ATP to power your
cellular machinery. Mitochondria is therefore thought of as the "
powerhouse" of the cell.
That is, if the
organism is
aerobic and uses oxygen as an
electron acceptor like
humans,
cats, and
fish, for example. If the eukaryote is
anaerobic instead, such as the
genera Trichomonas, hydrogenosomes are present in place of mitochondria.
Hydrogenosomes serve the same function as mitochondria, to convert
ADP to ATP, but lacks
cristae and
citric acid cycle enzymes.
To convert ADP to ATP, the hydrogenosome must have access to
pyruvate, which is obtained from
glucose metabolism. The pyruvate is oxidized to produce
hydrogen gas,
carbon dioxide gas, and
acetate. The energy liberated from this reaction is used by
ATP Synthase for ATP production.
Methanogens can sometimes be found living in the
cytoplasm of these eukaryotic cells in a
symbiotic relationship. These methanogens will consume the hydrogen gas produced by the
host organism, resulting in
methane gas.
Anaerobic eukaryotes are relatively rare.
Ciliates found in
rumen are an example of such, and
yeast can be considered
facultatively aerobic, meaning they can live without oxygen. According to Roberts (1998), anaerobic eukaryotes
evolved fairly recently.
Converted from
Brock Biology of Microorganisms, 10th Edition. Pearson Education, Inc. Upper Saddle River, NJ 07558. Pp 475 - 476.
Roberts, Dave. "Eukaryotes in Extreme Environments." http://www.nhm.ac.uk/zoology/extreme.html.