Electron Transport Chain and Oxidation Phosphorylation When one glucose molecule is oxidized to six CO 2 molecules by way of glycolysiss and TCA cycle, considerable amount of energy (ATP) is generated. Only four molecules of ATP are directly synthesized during the whole process while the rest of it comes from the oxidation of NADH and FADH 2 whichh takes place in an electron transport chain. The latter is composed of a series of electron carriers (cytochromes, coenzymes, etc.) which operate together to transfer electron from donors (e.g.. NADH. FADH 2) to acceptors (either O 2 in aerobic respiration or inorganic molecules like NO - 3, SO 2-4, CO 2, etc. Electron transport chain and oxidation phosphorylation. However, the processs of oxidation of NADH an to make ATP is called oxidative phosphoryla nd FADH 2 by ation. Both, which the en the ETC and nergy from electron transport chain is used oxidative phosphorylation The electron transport chain-carriers reside within the inner membrane of the mitochondrion in eukaryotic microoragnism (Mitochondrial ETC) whereas they are found in the plasma membrane of bacteria (bacterial ETC). Though, mitochondrial and.bacterial electron transport chains, frequently differ in details of their construction, they operate using the same fundamental principles. Bacterial ETCs vary in their electron carriers (e.g., cytochromes) and may be extensively branched. Also, electron often can enter at several points through several terminal oxidases. ATP-Yield in Glycolysis and TCA-Cycle Glycolysis Glucose Glucose 6-phosphate -1 ATP Fructose 6-phosphate Fructose 1, 6-bisphosphate 2 mol. [Glyceraldehyde-3-P 1, 3-bisphosphoglycerate] 2 mol. [1, 3-bisphosphoglycerate 3-phosphoglycerate] 2 mol. [Phosphoenolpyruvate Pyruvate] -1 ATP 2NADH 3 + 6 ATP +2 ATP +2 ATP + 8 ATP Pyruvate to Acetyl-CoA 2 mol. [Pyruvate Acetyl-CoA] TCA-Cycle (Kreb's Cycle) 2 NADH 3 + 6 ATP + 6 ATP
2 mol. [Isocitrate α-ketoglutyrate] 2 NADH 3 + 6 ATP 2 mol. [α- ketoglutyrate Succinyl CoA] 2 NADH 3 + 6 ATP 2 mol. [Succinyl-CoA Succinate] 2 GTP + 2 ATP 2 mol. [Succinate Fumarate] 2 FADH2 2 +4ATP 2 mol. [L-malate Oxaloacetate] 2NADH 3 + 6 ATP + 24 ATP Some question about glycolysis : Terms Definitions What is the net production of ATP during glycolysis? 2 ATP Why is pyruvate considered to be the end product of glycolysis? from pyruvate there are branch points (lactate production, acetyl coa, amino acid metabolism) What is the key regulatory enzyme in glycolysis? Why? PFK1 It catalyzes the first step requiring energy consumption (ATP) Phosphorylation of glucose creates? Glucose-6-phosphate Is the phosphorylation of glucose endergonic or exergonic? endergonic reaction In terms of permeability through membranes, what happens after the phosphorylation of glucose? Glucose-6-P cannot get across the membrane What redox reaction occurs between glyceraldehyde 3-phosphate and 1,3-bisphosphoglycerate?... What type of reaction takes place between 2,3-Bisphosphoglyerate to 3-Phosphoglycerate? substrate-level phosphorylation What is iodoacetate? binds, release hydride, toxin that inhibits glyceraldehyde-? What occurs between 3-phoshpglyerate and 2-Phosphoglycerate? repositioning of the phosphoryl group What is the last enzyme in the pathway? What type of reaction does it catalyze? substrate-level phosphorylation What inhibits? Why? high [ATP] enough energy is in the cell, no way to store it What activates? Fructose 1,6-bisphosphate Which 3 enzymes produce large decreases in standard free energy? hexokinase PFK
What happens to hydrogen ion concentration as lactate concentration increases? increases What type of conditions favor the formation of lactate? anaerobic conditions What is the name of the pathway that converts lactate to glucose in the liver? gluconeogenesis Insulin is indicative of which state? How does it affect glycolysis? fed state activates glycolysis Glucagon is indicative of which state? What is its effect on glycolysis? hungry state inhibits glycolysis ATP production in erythro cytes PPP What is the role of glycolysis (6)? TCA cycle NAD+ production anaplerotic intermediates for amino acid synthesis glycerol production for lipid synthesis What types of cells are completely dependent on glycolysis for energy? erythrocytes sodium transport across membrane of red blood cell... What is the purpose of hepatic glycolysis? buffer high blood glucose levels particularly following a CHO-rich meal What happens to NADH in aerobic conditions? re-oxidized in the ETC, making ATP via oxidative phosphorylation What happens to NADH in anaerobic conditions? NADH re-oxidized by lactate dehydrogenase to NAD+ to maintain glycolytic flux What are the 2 possible fates of pyruvate? aerobic: citric acid cycle anaerobic: LDH produces lactate Which enzymes catalyze substrate level phosphorylation reactions in the glycolytic pathway? What converts MeOH to formaldehyde? alcohol dehydrogenase ethanol drip How do you treat methanol poisoning (3)? bicarbonate hemodialysis
Why do you treat methanol poisining with ethanol? methanol has a higher affinity for alcohol dehydrogenase than MeOH How is ethylene glycol digested? What disorder occurs? converted to glycoaldehyde by alcohol dehydrogenase metabolic acidosis What type of glycolysis defect is fatal? genetic complete deficiency in glycolytic enzymes What happens in partial deficiency of glycolytic enzymes? hemolytic anemia (erythrocytes) What happens to RBCs in the case of deficiency? Cells swell and lyse ATP required for maintenance of Na+, K+ transporting- ATPases Describe the biochemistry behind mercury and arsenite poisoning (2)? both bind to dihydrolipoyl group of the pyruvate dehydrogenase complex deficiency of acetyl-coa leads to decreased production of acetylcholine, a neurotransmiter Which is more toxic? arsenite or arsenate? arsenite What type of enzymes are particularly susceptible to arsenite poisoning? Give 2 examples enzymes that use lipoic acid as cofactor PDH & a-ketoglutarate dehydrogenase... do not get the normal flux of ATP through the glycolytic pathway What enzyme of glycolysis is affected by fluoride? What kind of inhibitor is it, and where does it bind? enolase binding to the substrate at Mg2+ and phosphate strong competitive inhibitor... bacteria use sucrose to make a polysaccharide glue, forming bacterial plaque on surface of tooth erythrocytes What tissues depend on anaerobic glycolsyis? neonatal tissues adrenal medulla Where does the lens obtain glucose (2)? vitreous body and aqueous humor Why do the kidneys require large amounts of ATP? active transport Which part of the kidney is dependent on anaeerobic glycolysis? medulla *cortex is wells supplied What type of genetic disease is glucose 6 P dehydrogenase deficiency? X-linked
What disorder results from glucose-6-p dehydrogenase deficiency? NADPH deficiency in erythrocytes resulting in hemolytic anemia In what part of the cell does glycolysis occur? in the cytosol Name the 2 basic phases of glycolysis activation process (2 ATP molecules consumed) formation of pyruvate In order, list the intermediates of glycolysis glucose glucose-6-p fructose-6-p fructose-1,6-bisp dihydroxyacetone-p glyceraldehyde 3-P 2x 1,3-bisphosphoglycerate 2x 3-phosphoglycerate 2x 2-phosphoglycerate 2x phosphoenolpyruvate 2x pyruvate Goodness Gracious, Father Franklin Did Go By Picking Pumpkins (to) Prepare Pies Name the molecules involved in phase 1 glucose glucose-6-p fructose-1,6-bisp What enzyme catalyzes the phosphorylation of glucose? hexokinase (gluokinase in liver parenchymal cells and islet cells) Name the branch points of glucose-6-phosphate (3) PPP, glycogen storage, CHO synthesis What enzyme catalyzes the phosphorylation of fructose 6- phosphate? What is the product of this reaction? phosphofructokinase-1 fructose 1,6-bisphosphate What 2 molecules are formed from the cleavage of 1,6-phosphate? glyceraldehyde 3-phosphate dihydroxyacetone phosphate What enzyme catalyzes the cleavage of fructose 1,6-bisphosphate? aldolase A List 1 inhibitor and 2 activators of PFK-1 ATP AMP, fructose 2,6-bisphosphate What enzyme catalyzes phosphorylation of glyceraldehyde 3- phosphate? What is unique about this reaction? glyceraldehyde 3-phosphate dehydrogenase Pi is used; not ATP What enzyme catalyzes the reaction from 1,3-bisphosphoglycerate to 2,3-bisphosphoglycerate? mutase What enzyme catalyzes the reaction from 1,3-bisphosphogycerate to 3-phosphoglycerate? phosphoglyerate kinase
What enzyme catalyzes the reaction from 2,3-bisphosphoglycerate to 3-phosphoglycerate? phosphatase Phosphoglycerate mutase catalyzes which reaction? 3-phosphoglycerate to 2-phosphoglycerate Enolase catalyzes which reaction? 2-phosphoglycerate to phosphoenolpyruvate What enzyme catalyzes the formation of pyruvate from phosphoenolpyruvate? What type of regulation is under? allosteric glucokinase What enzymes (3) are affected by insulin and glucagon? phosphofructokinase Why does insulin stimulate hepatic glycolysis (2)? glucose-6-p initially directed towards glycogenesis acetyl-coa can be used as a precursor for fatty acid synthesis What enzyme converts pyruvate to lactate? lactate dehydrogenase What is disulfiram used in? alcohol aversion therapy What type of enzymes are particularly susceptible to arsenite poisoning? Give 2 examples enzymes that use lipoic acid as cofactor (PDH, a- ketoglutarate dehydrogenase) How does arsenate cause problems with glycolysis? competes for Pi-binding sites on enzymes, producing unstable arsenate esters At what stage of glycolysis does arsenate cause problems? How is this significant? glyceraldehyde 3 phosphate --> 1,3-bisphosphoglycerate 1 less ATP formed What enzyme of glycolysis is affected by iodoacetate? Where does it bind and how strongly? glyceraldehyde 3-P dehydrogenase cysteine residue (irreversible) In order, name the glycolysis enzymes hexokinase phosphoglucose isomerase phosphofructokinase Aldolase A triose phosphate isomerase glyeraldehyde-3-phosphate dehydrogenase phosphoglycerate mutase enolase High Profile People Act Too Glamorous, Picture Posing Every Place What is the mechanism behind fluoride? Inhibition of enolase