The Citric Acid Cycle Dr rer nat ubin Gulaboski：檸檬酸循環(huán)粗面內(nèi)質(zhì)網(wǎng)gulaboski NAT魯賓博士

1、joe maleszewskimarch 25, 2003lecture outline what is metabolism? review of glycolysis assault on pyruvate overview of krebs cycle (tca) reactions of krebs cycle regulation of krebs cycle where are we going next?metabolism metabolism is the sum of all chemical reactions within a cell (or whole organi

2、sm), including energy-releasing breakdown of molecules and the synthesis of complex molecules it is extraordinarily complexmetabolismthe reactions of metabolism are manyin this class we will discuss some of the major reactions: glyco - lysis (glycolysis) the citric acid cycle the electron transport

3、chainit is important to become familiar with some of the key players in these reactions atp nad/nadh the various other intermediate compounds (many are sugars)adenosine triphosphate (atp) used primarily as the “chemical-storage” form of energy within the cell.nicotinamide adenine dinucleotide (nad)

4、used primarily in the cell as an electron carrier to mediate numerous reactionsreductionoxidationnicotinamide adenine dinucleotide (nad) used primarily in the cell as an electron carrier to mediate numerous reactionsreductionoxidationreview of glycolysis whats the point of glycolysis? traps glucose

5、within the cell produces energy in the form of nadh and atp with minimal energy input produces products that are used in other metabolic pathways within the cell many more reasonsreview of glycolysiswhat have we put in to this?atpx 2nad x 2what are we getting out of it?atpx 4adp x 4nadh x 2adpx 2rev

6、iew of glycolysisthe fate of pyruvate in the absence of oxygen - pyruvate gets fermented to oxidize nadh to nad so that glycolysis (atp production can continue.the fate of pyruvate in the presence of oxygen - pyruvate gets turned into acetyl coa and then added to other molecules in order to liberate

7、 co2 (the calvin cycle - backwards).the assault on pyruvate pyruvate moves easily passed the porous outer mitochondrial membrane and is then transported through the inner membrane where it encoutersthe pyruvate dehydrogenase multienzyme complexthe assault on pyruvate the pyruvate dehydrogenase multi

8、enzyme complex will “assimilate” pyruvate into acetyl coa by “ripping off” pyruvates co2 “head” and attaching chemical parts to its “neck.”the assault on pyruvatethe assault on pyruvateacetyl coa moves on to the kreb cycle (the citric acid cycle)regulation of krebs cycle the regulation is mediated v

9、ia allosteric inhibition by products on enzymes used previously in the cycle. for example, an increase in citrate will cause a decreased activity of citrate synthase an increased nadh or acetyl coa will decrease pyruvate dehydrogenase activity where have we been?krebs cycle summary remember, we get

10、3-nadh from tca along with the one we got from the pyruvate dh reaction and then an fadh2 (a lot like nadh, but less reducing power) and an atp and this is just from one pyruvate molecule (remember: 2 pyruvates per glucose molecule)where are we going? the nadh from glycolysis & the nadh + fadh from the citric acid cycle will now move on to the electron transport chain.why? the atp that we will yield fro