Background Information

-Background Information: Yeasts are eukaryotic organisms belonging to the kingdom of Fungi. They are single-celled organisms which generally resemble oval or round blobs (“Yeast” Columbia, 1). Yeast cells can reproduce through two main methods: budding and fission (Ashe, 1). In budding, a small portion of the yeast’s cell wall swells up. This portion, called a bud, detaches itself from the rest of the yeast and becomes its own cell (Ashe, 1). Below is a color-enhanced micrograph of budding yeast cells:

moz-screenshot.jpgmoz-screenshot-1.jpg
budding_yeast.jpg
"Budding Yeast." <http://www.phys.ksu.edu/gene/photos/lc.html> 2/12/08


Yeasts can perform cellular respiration using two different methods: aerobic and anaerobic respiration, making them facultative anaerobes (Campbell, 103). When in the presence of O2, yeasts can produce ATP through chemiosmosis. In this case, the formula for aerobic respiration is given as:

C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP (between 36 and 38)

Yeast cells are also capable of anaerobic respiration, using only glycolysis to generate ATP, and giving of ethyl alcohol as a byproduct. This process is known as alcoholic fermentation (Campbell, 103). When applied to glucose, the formula for alcoholic fermentation is given as:

C6H12O6 --> 2 CH3CH2OH + 2 CO2 + ATP (about 2)

One of the most important species of yeast is Saccharomyces cerevisiae. This species, as well as closely related strains, is used to ferment alcoholic drinks such as beer, and in baking to make dough rise (“World-Wide Web Yeast”, 1).

-Citations:

Ashe, Arthur J. , III. "Yeast." World Book Online Reference Center. 2008. 12 Feb. 2008
http://www.worldbookonline.com/wb/Article?id=ar613160

Campbell, Neil A, Lawrence Mitchell, and Jane Reece. Biology: Concepts and
Connections. San Francisco, California: Benjamin/Cummings, 2000.

“The World-Wide Web Virtual Library: Yeast.” 2005. WWW Virtual Library. 2/12/08
http://www.yeastgenome.org/VL-yeast.html

“Yeast.” The Columbia Encyclopedia, 6th ed. New York: Columbia University Press,
2001–07. 2/12/08. http://www.bartleby.com/65/ye/yeast.html