Metabolism Harvesting energy from molecules (catabolism)

1. Metabolism Harvesting energy from molecules (catabolism) Using energy to synthesize molecules and their subunits: synthesis of sugars, amino acids, etc. How do organisms harvest energy?

3. Cells use metabolic pathways to control and use energy released in catabolism Through stepwise metabolic pathways

4. p. 132

5. Enzymes lower activation energy (are catalysts) are specific are proteins (i.e., sensitive to environmental conditions)

6. p. 133

7. What about those electrons? In these reactions, electrons are donated by (removed from) the energy source and transferred to another compound The energy source is oxidized The recipient molecule is reduced Some molecules function in the cell as electron carriers (they are reduced and then oxidized)

8. Major electron carriers NAD+, FAD: participate ultimately in ATP synthesis A terminal electron acceptor is required In aerobes it is oxygen In anaerobes it is something else NADP+ is used in biosynthetic pathways

9. Precursor metabolites Are used in catabolic pathways Can be used in anabolic pathways, too Many microbes can make all cell components (including all amino acids) from precursors (they can grow in minimal medium)

10. p. 135

11. p. 136

12. Glycolysis, Krebs, ETC/OP look familiar Some bacteria use variations on glycolysis (still get pyruvate, but different intermediates are formed) Pentose phosphate pathway can also be used for energy, but is more commonly used to make 5-carbon sugars (where do you find these?)

13. Respiration Lots of reducing power (NADH, FADH2) Terminal electron acceptor required to regen- erate electron carrier (oxygen, nitrate, carbon dioxide or other inorganic molecule) If not available, cells cannot respire Some can ferment instead pyruvate or derivative is used as terminal electron acceptor

14. Why can organism not respire? No terminal electron acceptor is available Some are “obligate fermenters” (can’t use oxygen although they are not killed by it) example: lactic acid bacteria They get their ATP from glycolysis Different organisms have different fermentation pathways

17. These differences can be commercially useful, or can be useful in identification Glycolysis (or variant, producing pyruvate) and Krebs (TCA) cycle are common to respiring cells Prokaryotes: whole process occurs in cytoplasm Eukaryotes: oxidative decarboxylation of pyruvate is required in process of getting into the mitochondrion (where Krebs cycle occurs)

18. glycolysis

19. Krebs cycle

20. Aerobic respiration Electron transport chain (energy from electrons is released; proton gradient is generated Oxidative phosphorylation: proton motive force is used to synthesize ATP

21. In inner mitochondrial membrane

22. In plasma membrane of E. coli

23. Anaerobic respiration is less efficient less energy released in reduction of compounds other than oxygen Different electron carriers Several pathways exist for reducing nitrate

25. What do organisms use for energy? Organotrophs can use many organic molecules besides glucose, if they have the right enzymes Polysaccharides- amylase, cellulase Disaccharides must be converted to mono- saccharides Monosaccharides (like mannose or galactose) must be modified Lipases, proteases

26. Chemolithotrophs can use inorganic substances for energy; many of these are products of anaerobic respiration p. 155

27. Photosynthesis Photosynthetic organisms convert light energy to chemical energy They are the ultimate energy source for everything else Pigments are used to capture light (radiant) energy Generate ATP; also reducing power to fix CO2 and form sugar (C6H12O6)

28. p. 157

29. Prokaryotes tend to be similar in anabolic processes Use ATP Use NADPH for reducing power Have enzymes to make precursors and put them together to form macromolecules Fastidious organism don’t have the enzymes, so macromolecules must be provided Lipids Amino acids Nucleic acids