Daily Newsletter February 21, 2012

Daily Newsletter February 21, 2012

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Today's Topic: Gylcolysis

Here is one of the best images of glycolysis online. Feel free to use this as a reference when working through glycolysis.

 Today your goal is to review and reflect upon the second five steps of glycolysis.  These are referred to as the energy harvesting steps.  As with yesterday, I am only going to focus on one reaction:  Step 6. 

Step 6 is catalyzed by Glyceraldehyde Phosphate Dehydrogenase.  The word dehydrogenase explains the action.  We are removing hydrogens.  When we remove hydrogens, we also remove electrons.  Dehydrogenases are responsible for oxidizing a substrate.  So this is a redox reaction.  You can also tell this because our electron carrier NAD is being reduced as a by product of this reaction.  So we remove electrons (energy) from Glyceraldehyde 3-P and give electrons (energy) to NAD, forming NADH.

This is the single largest change in energy throughout glycolysis.  This is a major harvesting of energy (we harvest the most energy using redox reactions). 

Notice that we are also adding a phosphate.  But why?  We do not use ATP to add this phosphate.  We use an inorganic phosphate.  One reason is to maintain the stability of the molecule.  When substrates are oxidized, the molecule becomes unstable.  Sometimes the instability is needed for the next reaction, but sometimes the instability is just a little too much.  There is an intermediate here that is unstable, so we add Phosphate to stabilize the product.

But notice, the new phosphate is highlighted in yellow.  Why?  This is a notation used by the artist to represent a high energy phosphate.  On either end of the 1,3 bisphophoglycerate there is a phosphate group, a -2 phosphate group.  You have negative charges being held in close association.  Is this electrically stable?  No, the negative charges want to push away from each other.  Thus we get a "high energy" bond (one that is stable, but easily broken).

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Daily Challenge: Energy Harvesting Steps of Glycolysis
I did not give you all of the information about reaction 6. Just enough to start you off. Go through reaction 6-10. Feel free to quote (and reference) other material to build descriptions of these reactions. After building descriptions, reflect upon what these descriptions are saying. Put the reaction into your own words.