Tuesday, October 20, 2009
Born on October 12, 1885, Arthur Harden shared the 1929 Nobel Prize in chemistry for his work elucidating the glycolytic pathway. This is the pathway by which glucose and other sugars are broken down into smaller molecules and energy is extracted in living cells. Arthur Harden discovered posphorylated intermediates along this pathway and he characterized glucose phosphate and fructose diphosphate, two of the molecules along the pathway.
It has been known since ancient times that fruit juices and other sugar containing liquids, under the right conditions, undergo fermentation. Fermentation is the process by which microorganisms convert sugar into alcohol. Ancient cultures used knowledge of fermentation to produce wine and beer.
The glycolytic pathway is a number of steps in which a six-carbon long sugar molecule is broken down into two three-carbon pyruvate molecules (a really cool discussion of all the steps can be found here). This pathway occurs in nearly all biological organisms, both aerobic (those using oxygen) and anaerobic (those that don't use oxygen). Each sugar molecule that goes through the pathway produces two molecules of pyruvate, two molecules of hydrogenated nicotinamide adenine dinucleotide (NADH+) and two molecules of adenosine triphosphate (ATP). ATP is the primary molecule by which living cells store and transfer chemical energy.
In order to get the glycolytic pathway started two molecules of ATP are used to add phosphate to the six-carbon sugar molecule. The addition of the first phosphate produced glucose phosphate and the addition of the second phosphate produces fructose diphosphate (the two molecules that Arthur Harden characterised). This six-carbon sugar diphosphate is then broken down (through a number of steps) into two three carbon molecules, each of which will add phosphate to two molecules of adenosine diphosphate (ADP) to make two molecules of ATP. In summary two molecules of ATP are used to energize the process which will produce four molecules of ATP, giving a net production of two molecules of ATP for each molecule of sugar that is broken down.
For his work studying the glycolytic pathway Arthur Harden is the Dead Scientist of the Week for the week of October 11-18, 2009.
Arthur Harden, Wikipedia Entry
Glycolysis, Wikipedia Entry
Moran, Laurence, a blog entry on Arthur Harden