Enzymes are proteins that accelerate, or catalyze, chemical reactions. In these reactions, molecules called substrates are converted by enzymes into different molecules called products. Almost all processes in the cell need enzymes in order to occur at significant rates. Like all catalysts, enzymes work by providing an alternative path of lower activation energy for a reaction and dramatically increasing its rate; some enzymes can make the conversion of substrate to product occur many millions of times faster. Enzymes are not consumed in chemical reactions, nor do they alter the equilibrium of a reaction. However, enzymes do differ from most other catalysts by being much more specific. Since enzymes are extremely selective for their substrates and speed up only a few reactions, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. Many drugs and poisons work by inhibiting enzyme activity.

Read the rest of this article: http://en.wikipedia.org/wiki/Enzyme

_______________________________ Today's selected anniversaries:

1850: The University of Sydney, Australia's oldest university, was established in Sydney. (http://en.wikipedia.org/wiki/University_of_Sydney)

1865: The Morant Bay rebellion, led by Paul Bogle and George William Gordon, began in Jamaica and was brutally suppressed by Governor Edward John Eyre. (http://en.wikipedia.org/wiki/Morant_Bay_rebellion)

1899: The Second Boer War erupted in South Africa between the United Kingdom and the Boers. (http://en.wikipedia.org/wiki/Second_Boer_War)

1954: Ho Chi Minh and the Viet Minh took control of North Vietnam. (http://en.wikipedia.org/wiki/Viet_Minh)

1968: NASA launched Apollo 7, the first manned mission of the Apollo program. (http://en.wikipedia.org/wiki/Apollo_7)

_____________________ Wikiquote of the day:

It takes courage to love, but pain through love is the purifying fire which those who love generously know. We all know people who are so much afraid of pain that they shut themselves up like clams in a shell and, giving out nothing, receive nothing and therefore shrink until life is a mere living death. -- Eleanor Roosevelt (http://en.wikiquote.org/wiki/Eleanor_Roosevelt)