Metabolism cont’d

Carbohydrate Catabolism

Carbohydrate Catabolism cont’d

Summary of Carbohydrate Catabolism

TCA Cycle (Krebs Cycle) 2 acetyl-CoA groups are oxidized in the Krebs cycle for each glucose molecule (1 six-carbon glucose is oxidized to two 3 carbon pyruvic acid molecules, each of which is decarboxylated to produce an acetyl-CoA molecule).  Electrons are picked up by NAD+ and FAD for the electron transport chain. From one molecule of glucose, oxidation in the Krebs cycle produces 6 molecules of NADH, 2 molecules of FADH2, and 2 molecules of ATP. Decarboxylation produces 6 molecules of CO2.

TCA Cycle (Krebs Cycle)

Electron Transport Chain As electrons are passed from carrier to carrier in the chain, they decrease in energy and some of the energy lost is harnessed to make ATP

Summary In aerobic prokaryotes, 38 ATP molecules can be produced form complete oxidation of a glucose molecule in glycolysis, the Krebs cycle, and the electron transport chain.   In eukaryotes, 36 or 38 ATP molecules are produced from complete oxidation of a glucose molecule (in some tissues 2 ATP are required to shuttle the 2 electrons from the NADH produced in glycolysis across the mitochondrial membrane to the electron transport chain, in others there is no energy cost and 38 ATP are gained per mole of glucose).

Summary of Respiration Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen O2 Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycle operates under anaerobic condition

Anaerobic Respiration Electron acceptors other than oxygen are used i.e.: Inorganic oxygen containing molecules such as Nitrate (NO3-), Sulfate (SO42-), Ferric iron (FE3+), Carbonate (CO32-) and Perchlorate (ClO4-) Less energy is released Permits microorganisms to respire in anoxic environments

Fermentation Any spoilage of food by microorganisms (general use) Any process that produces alcoholic beverages or acidic dairy products (general use) Any large scale microbial process occurring with or without air (common definition used in industry)

Fermentation cont’d Scientific definition Release of energy from organic molecules Does not require oxygen Does not use the Krebs cycle of Electron transport chain Uses organic molecule as the final electron acceptor

Types of Fermentation

Fermentations By Naturally-Occurring Organisms PRODUCT APPLICATION ORGANISM Bacitracin Antiobiotic Bacillus subtilis (bacterium) Chloramphenicol Streptomyces venezuelae (bacterium) Citric acid Food flavoring Aspergillus niger (fungus) Erythromycin Antibiotic Streptomyces erythaeus (bacterium) Invertase Candy Saccharomyces cerevisiae (fungi) Lactase Digestive aid Escherichia coli (bacterium) Neomycin Streptomyces fradiae (bacterium) Pectinase Fruit juice Penicillin Penicillium notatum (fungus) Riboflavin Vitamin Ashbya gossypii (fungus) Streptomycin Streptomyces griseus (bacterium) Subtilisins Laundry detergent Tetracycline Streptomyces aureofaciens (bacterium)

Fermentations By Genetically Engineered Organisms PRODUCT APPLICATION ORGANISM B. growth hormone Milk production(cows) Escherichia coli (E. coli) Cellulase Cellulose E. coli H. growth hormone Growth deficiencies E.coli Human insulin Diabetics Monoclonal antibodies Therapeutics Mammalian cell culture Ice-minus Prevents ice on plants Pseudomonas syringae Sno-max Makes snow t-PA Blood clots Tumor necrosis factor Dissolves tumor cells

Fermentation Alcohol fermentation: Produces ethanol and CO2 Lactic acid fermentation: Produces lactic acid -homolactic fermentation: Produces lactic acid only -heterolactic fermentation: Produces lactic acid and other compounds

Final Electron Acceptor Electron carriers Final electron acceptor Oxygen O2 Aerobic respiration Other inorganic molecules (NO3-), (SO42), (FE3+), (CO32-) & (ClO4-) Anaerobic respiration Organic molecules Pyruvic acid Fermentation