The document summarizes the stages of aerobic respiration in bacteria. It begins with glycolysis which produces pyruvic acid and ATP without oxygen. The Krebs cycle then converts pyruvate into carbon dioxide while producing more ATP and NADH. Finally, the electron transport chain uses the NADH to power ATP synthesis via chemiosmosis. Overall, the aerobic respiration of one glucose molecule yields 38 ATP.

2.  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
 Electron transport chain

3. Overview of bacterial aerobic respiration

4.  First stage in carbohydrate catabolism
 Oxidation of glucose to pyruvic acid
 Located in the cytoplasmic matrix of prokaryotes and eukaryotes
 Also called the Embden-Meyerhof pathway
 Does not require oxygen; it can occur whether oxygen is present
or not
 Two molecules of ATP are produced
 Consists of two basic stages; preparatory stage and energy-
conserving stage

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

6. The Pentose Phosphate Pathway
 Also called the hexose monophosphate pathway
 Occurs in the cytosol of the cell
 No ATP is directly consumed or produced in the cycle
 Operate 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 most common route for the conversion of hexoses to
pyruvate
 Generally found in Pseudomonas, Rhizobium, Azotobacter,
Agrobacterium and Enterococcus faecalis

9. The Entner-Doudoroff Pathway

10.  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 CO2
 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
 The 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
 One of Krebs cycle’s major functions is to provide carbon
skeletons for biosynthesis

12. The Krebs cycle

13.  Consists of a sequence of carrier molecules that are capable of
oxidation and reduction
 Electrons are passed through the chain
 Stepwise 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
 In 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
 Contain flavin, a coenzyme derived from riboflavin (vitamin B2)
 Capable of performing alternating oxidations and reductions
 One important flavin coenzyme is flavin mononucleotide
(FMN)

16. Cytochromes
 Proteins with an iron-containing group (heme)
 Capable of existing alternately as a reduced form (Fe2+) and an
oxidized form (Fe3+)
 The cytochromes involved in electron transport chains include
cytochrome b (cyt b), cytochrome c1 (cyt c1), cytochrome c
(cyt c), cytochrome a (cyt a), and cytochrome a3 (cyt a3)
Ubiquinones, or coenzyme Q
 small non-protein carriers

17. An electron transport chain

18.  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
 Energy 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