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Biochemical Pathways of Energy Metabolism
Series of controlled reactions rather than in a single burst.
Carbohydrate Metabolism
Glycolysis – Embden Meyerhoff Pathway
Oxidation of glucose to pyruvic acid, series of 10 reactions, each reaction catalyzed by a different enzyme
Carbohydrate metabolism
Pentose Phosphate Pathway – hexose monophosphate shunt
Operates simultaneously with glycolysis Provides a means for the breakdown of
5 carbon sugars as well as glucose
Carbohydrate Metabolism
EDP is still another pathway for oxidizing glucose to pyruvic acid
Yield 1 ATP
Fermentation of Carbohydrates
Glucose Pyruvic Acid fermentation or respiration
Release energy from sugars or other organic molecules such as amino acids, organic acids, purines and pyrimidines
Does not require oxygen Does not require an electron transport
chain
Fermentation of Carbohydrates
Uses an organic molecule as the final electron acceptor
Fermentation
Products – ethanol and carbon dioxide Brewing and wine making are anaerobic
processes if oxygen is present further oxidation will occur
Respiration
Is an ATP generating process in which chemical compounds are oxidized and the final electron acceptor is almost always an inorganic molecule
Electron transport chain – readily accept electrons from one compound and pass them to another
ATP generated by oxidative phosphorylation
Respiration
Oxidize organic molecules completely to carbon dioxide
ATP yield greater in respiration than in fermentation
Krebs Cycle
As acetyl CoA enters the Krebs cycle, CoA detaches from the acetyl group and then can pick up more acetyl groups for the next Krebs cycle
Series of redox reactions Yield 38 ATP
Protein Catabolism
Require extracellular enzymes – proteases and peptidases
Deaminate amino acids Decarboxylation
Lipid Catabolism
Fats fatty acids + glycerol Requires lipases Convert glycerol into dihydroxyacetone
phosphate Fatty acids catabolized by beta
oxidation
Energy Utilization
Microbes use ATP to provide energy for the transport of substances across plasma membranes
For flagellar motion Biosynthesis of new cell components
Biosynthesis of Polysaccharides
Bacteria synthesize glycogen from adenosine diphosphoglucose – ADPG
Synthesize capsular material
Biosynthesis of Lipids
Microbes synthesize lipids, by uniting glycerol and fatty acids
Structural components of plasma membrane and Gram – cell wall
Lipids serve as storage forms of energy
Biosynthesis of Amino Acids
Required for protein synthesis E. coli – synthesize all the amino acids
they need Other microbes require some preformed
aa from the environment in order to metabolize proteins
Krebs cycle source of precursors for aa
Biosynthesis of Amino Acids
Other sources of precursors are derived from the pentose phosphate pathway and the EDP
AA building blocks for proteins (toxins)
Biosynthesis of Purines & Pyrimidines
Sugars composing nucleotides are derived from either the PPP or the EDP
Aspartic acid, glycine and glutamine play an essential role in the biosynthesis of purines and pyrimidines
The C and N atoms derived from these aa form the backbone of the purines and pyrimidines
Integration of Metabolism
Anabolic and catabolic reactions are integrated through a group of common intermediates
Krebs cycle – operate in both anabolic and catabolic reactions produce intermediates that lead to the synthesis of amino acids, fatty acids and glycerol – amphibolic pathways