Bacterial aerobic respiration

Bacterial aerobic respiration

1. BACTERIAL AEROBIC RESPIRATION

2. INTRODUCTION Oxygen serves as the terminal electron acceptor for the electron-transport chain in aerobic respiration The aerobic respiration in bacteria typically occurs in three principal stages Glycolysis Krebs cycle E lectron transport chain

3. Overview of bacterial aerobic respiration

4. Glycolysis F irst stage in carbohydrate catabolism O xidation of glucose to pyruvic acid L ocated in the cytoplasmic matrix of prokaryotes and eukaryotes A lso called the Embden -Meyerhof pathway D oes not require oxygen; it can occur whether oxygen is present or not T wo molecules of ATP are produced C onsists of two basic stages; preparatory stage and energy-conserving stage

5. An outline of the reactions of glycolysis Preparatory stage Energy-conserving stage

6. Alternatives to Glycolysis The Pentose Phosphate Pathway A lso called the hexose monophosphate pathway O ccurs in the cytosol of the cell No ATP is directly consumed or produced in the cycle O perate either aerobically or anaerobically Bacteria that use the pentose phosphate pathway include Bacillus subtilis , E . coli, Leuconostoc mesenteroides and Enterococcus faecalis

7. Irreversible oxidative reactions Reversible non-oxidative reactions The Pentose Phosphate Pathway

8. The Entner-Doudoroff Pathway T he most common route for the conversion of hexoses to pyruvate G enerally found in Pseudomonas, Rhizobium, Azotobacter , Agrobacterium and Enterococcus faecalis

9. The Entner-Doudoroff Pathway

10. Krebs cycle Also called the tricarboxylic acid (TCA) cycle or citric acid cycle Large amount of energy stored in acetyl CoA is released step by step Oxidative decarboxylation of pyruvate Pyruvate is converted to acetyl CoA and CO 2 It is not part of the Krebs cycle, but is a major source of acetyl CoA NAD + is reduced to NADH Acetyl-CoA arises from the catabolism of many lipids, carbohydrates and amino acids

11. The complete cycle appears to be functional in many aerobic bacteria, free-living protozoa, and most algae and fungi T he facultative anaerobe E. coli does not use the full Krebs cycle under anaerobic conditions or when the glucose concentration is high but does at other times O ne of Krebs cycle’s major functions is to provide carbon skeletons for biosynthesis

12. The Krebs cycle

13. The Electron Transport Chain C onsists of a sequence of carrier molecules that are capable of oxidation and reduction E lectrons are passed through the chain S tepwise release of energy Which is used to drive the chemiosmotic generation of ATP The final oxidation is irreversible In eukaryotic cells - the electron transport chain is contained in the inner membrane of mitochondria I n prokaryotic cells - it is found in the plasma membrane

14. Glucose metabolism and the electron transport chain of bacteria

15. There are three classes of carrier molecules in electron transport chains Flavoproteins C ontain flavin , a coenzyme derived from riboflavin (vitamin B 2 ) C apable of performing alternating oxidations and reductions One important flavin coenzyme is flavin mononucleotide (FMN)

16. Cytochromes P roteins with an iron-containing group ( heme ) Capable of existing alternately as a reduced form (Fe 2+ ) and an oxidized form (Fe 3+ ) The cytochromes involved in electron transport chains include cytochrome b ( cyt b), cytochrome c 1 ( cyt c 1 ), cytochrome c ( cyt c), cytochrome a ( cyt a), and cytochrome a3 ( cyt a 3 ) Ubiquinones , or coenzyme Q small non-protein carriers

17. An electron transport chain

18. The Chemiosmotic Mechanism of ATP Generation Chemiosmosis - the mechanism of ATP synthesis using the electron transport chain The movement of materials across membranes from areas of high concentration to areas of low concentration; this diffusion yields energy E nergy released is used to synthesize ATP

19. Electron transport and the chemiosmotic generation of ATP

20. Source ATP yield (Method) Glycolysis Oxidation of glucose to pyruvate 2 ATP (substrate level phosphorylation) Production of 2NADH 6 ATP (oxidative phosphorylation in electron transport chain) Preparatory step Formation of acetyl CoA produces 2 NADH 6 ATP (oxidative phosphorylation in electron transport chain) Krebs cycle Oxidation of succinyl CoA to succinate 2 GTP (equivalent of ATP; substrate level phosphorylation) Production of 6 NADH 18 ATP (oxidative phosphorylation in electron transport chain Production of 2FADH 4 ATP (oxidative phosphorylation in electron transport chain) Total: 38 ATP ATP yield during prokaryotic aerobic respiration of one glucose molecule

21. THANKS