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Dual Role of Oxidation in Metabolism: Building Blocks and Energy Source

Explore the metabolic pathways of oxidation and reduction in Mycoplasma pneumoniae, a genome-reduced bacterium, focusing on energy production and simplified biochemical reactions. Learn about essential coenzymes and the significance of redox reactions in cellular processes.

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Dual Role of Oxidation in Metabolism: Building Blocks and Energy Source

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  1. Oxidation has a dual role: building blocks and energy In our high O2 environment: reduced compounds seem more energetic e.g., C: most reduced: CH4 Highly negative DGo’ for oxidation -CH2-CH3 -CH2-CH2-OH -CH2-CH=O -CH2-COOH most oxidized O=C=O Positive/zero DG o’ for oxidation

  2. A metabolic map

  3. A metabolic map

  4. Mycoplasma pneumoniae has a simple structure and reduced metabolism Proteome Organization in a Genome-Reduced Bacterium Kühner, et al., Science 326, 1235 (2009)

  5. The biochemistry of M. pneumoniae is much simpler than that shown earlier.

  6. We will focus on a subset of the pathways in M. pneumoniae, but also add oxidative energy metabolism (citric acid cycle, electron transport system), photosynthesis and a little bit of amino acid metabolism.

  7. ATP provides energy and phosphate

  8. NADH (nicotinamide adenine dinucleotide) carries electrons (reducing power) and energy NADH + H+ --> NAD+ + 2 H+ + 2 e- DGo’ = -62 kJ/mol (Reversed, NAD+ is a useful oxidizing agent, e.g., alcohols -C-OH to aldehydes -CH=O)

  9. FADH2 --> FAD + 2 H+ + 2 e- DGo’ = -0.6 to -17 kJ/mol (FAD is another useful oxidizing agent e.g., -CH2-CH2- --> -CH=CH-)

  10. Coenzyme A (CoA, CoA-SH) carries 2-carbon units + O CH3-C-R O CH3-C-S-CoA + HR

  11. Since animals cannot synthesize most coenzymes, the coenzymes (or their precursors) are vitamins (that is, must be obtained in the diet). Coenzyme A FAD, FMN NAD pyridoxal phosphate

  12. Deficiencies of vitamins and their coenzymes are pathological Deficiency causes: Hypertension Cheliosis Pellagra: Depression photophobia dermatitis confusion dermatitis diarrhea convulsions insanity

  13. Summary • The diverse chemicals in the cell are linked by synthetic and degradative • reactions arranged in pathways. • Redox reactions are essential for synthesis and for applying energy (G). • Various coenzymes are mediators of energy, electron, and carbon-unit • transfers in metabolism (you need to know the essential structures and • reactions of ATP, NAD+/NADH, FAD/FADH2, and CoA).

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