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Unformatted text preview: Monday, October 24, 2011 Lecture 25 Announcements For this week's lectures ( Quiz on 11/2 ), assignments are as in LG for 10/26, 10/28, and 10/31 AND no PyMOL for the quiz on 11/2 (and for the lectures this week). Friday's lecture: Bioenergetics: Redox rxns can be interesting, and are very important in biology; Relation between free energy and redox potential difference Vast number of unexpected interconnections in metabolism Intro to glycolysis TODAY: pp. 187-188 The notion of glycolysis as a "chemical factory" for the cell: . Glucose-6-phosphate can be made into other sugars, and other sugars can be made into G6P. In addition, G1P, released from glycogen, is interconverted with G6P. . Fructose-6-phosphate is the entrance point for other sugars. Also, F6P can be made into amino sugars, which can be made into glycolipids and glycoproteins. From here, glycolsaminoglycans can be made. . Glyceraldehyde-3-phosphate is made into dihydroxyacetone phosphate (DHAP), which can be used for lipid synthesis. . 1,3 bisphosphoglycerate can be made into 2,3 bisphosphoglycerate, which you remember is essential for proper hemoglobin function. . 3-phosphoglycerate is used for serine synthesis. . Phosphoenolpyruvate is used for amino acid synthesis also, as is pyruvate. p. 188 Prof. traced through the "big map of metabolism" to show how a glycolysis intermediate, DHAP, is connected to nucleotide synthesis, and also to lipid synthesis. p. 189 Lots of free energy is available when glucose is oxidized completely: Glucose + 6 O 2 6 CO 2 + 6 H 2 O G o ' for this reaction, the complete oxidation of glucose, is - ~3,000 kJ/mole. ADP + P i ATP + H 2 O For ATP synthesis from ADP and P i , G o ' = +31 kJ/mole and G is ~ 50kJ/mole. Cells could make ~ 60 ATP with the energy from completely oxidizing glucose! But in glycolysis, glucose is only partially oxidized . In fact, oxidation occurs only in step 6, when an aldehyde is oxidized to a (phosphate) ester. This one step of carbon oxidation has a G o ' of about -150 kJ/mole, sufficient to drive synthesis of several ATPs. In addition, this one step occurs twice for every one glucose molecule that goes through glycolysis. Now let's look at some simple organic chemistry in order to understand the "strategy" of the first four reactions. Carbon-carbon bond breaking- there are only two ways to do it! 1. At the top of p. 190 is the free-radical reaction. In this case, the electron density of the C - C bond is split evenly, creating two free-radicals (jargon: unpaired electrons). Such reactions are rarely seen in the controlled rxns of metabolism: free radicals react rapidly with nearby atoms, yet the essence of metabolism is that all reactions are catalyzed, hence under control.metabolism is that all reactions are catalyzed, hence under control....
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This note was uploaded on 01/01/2012 for the course BIOMG 3310 taught by Professor Feigenson during the Fall '11 term at Cornell University (Engineering School).
- Fall '11