This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: Glucose 2x pyruvate Glycolysis Gluconeogenesis lactate ethanol anaerobic acetylCoA TCA Cycle NADH FADH 2 Oxidative phosphorylation ATP aerobic The course can be divided roughly into two sections: degradation (usually coupled to conversion of released energy into ATP) and biosynthesis. We will begin with a review of the core of metabolism that was touched on at the end of 2360: glycolysis, the tricarboxylic acid (TCA) cycle and oxidative phosphorylation involving the electron transport chain (ETC). As will become evident as we progress through the various sections, virtually all of metabolism is linked back to this core pathway and can easily be thought of as branches leading from or to the core. It is important to realize therefore that, while we often asign the role of ATP generation to this section, it is equally important for producing many of the intermediates required in biosynthetic pathways and also for metabolizing products from other degradative pathways. Of course, remember: ' G' o = -RTlnK' eq and ' G' o = -n ' E' o C a r b o h y d r a t e C a t a b o l i s m f o r A T P G e n e r a t i o n 1. G l y c o l y s i s a n d G l u c o n e o g e n e s i s The term " glycolysis " literally means the breakdown of sugar, but has come to be used to refer specifically to the breakdown of glucose to pyruvate. The term " gluconeogenesis " means literally the birth or generation of glucose and has come to refer to the reversal of glycolysis involving a few specific enzymes in addition to those in the glycolysis pathway. As with many pathways, the first step of glycolysis catalyzed by hexokinase is irreversible, and commits the carbohydrate to the degradative pathway. This also requires a separate enzyme to reverse the process, glucose-6-phosphatase . 1 - 1 Lec #2 O HOH 2 C HO OH OH O O 3 POH 2 C HO OH OH ATP ADP Hexokinase ' G' o =-16.7 kJ/mol H 2 O Pi Glucose-6-phosphatase ' G' o =-13.8 kJ/mol Glucose Glucose-6-phosphate (Glc-6-P) 2 O O 3 POH 2 C HO OH OH Glc-6-P 2 O OH OH CH 2 OPO 3 2 OH CH 2 OH Fructose-6-phosphate (Frc-6-P) Phosphoglucose isomerase ' G' o =+1.7 kJ/mol O OH OH CH 2 OPO 3 2 OH CH 2 OH Frc-6-P O OH OH CH 2 OPO 3 2 OH CH 2 OPO 3 Fructose-1,6-bisphosphate (Frc-1,6-bisP) ATP ADP Phosphofructokinase ' G' o =-16.7 kJ/mol H 2 O Pi Fructose-1,6-bisphosphatase ' G' o =-13.8 kJ/mol 2 1 2 3 Phosphofructokinase is also an irreversible reaction in vivo necessitating the need for a separate enzyme to reverse the process for gluconeogenesis. These two enzymes make up the site at which the glycolysis pathway is regulated, and the key concept underlying control is energy levels. The reaction progressing to the right (energy release) occurs under conditions of low energy, while the reaction to the left (glucose synthesis for energy storage) occurs under conditions of high energy....
View Full Document
This note was uploaded on 02/27/2011 for the course MBIO 2370 taught by Professor Spearman during the Winter '11 term at Manitoba.
- Winter '11