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Metabolism Is the Sum of Cellular Reactions

Metabolism Is the Sum of Cellular Reactions. Metabolism - the entire network of chemical reactions carried out by living cells Metabolites - small molecule intermediates in the degradation and synthesis of polymers

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Metabolism Is the Sum of Cellular Reactions

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  1. Metabolism Is the Sum of Cellular Reactions • Metabolism - the entire network of chemicalreactions carried out by living cells • Metabolites - small molecule intermediates in the degradation and synthesis of polymers • Catabolic reactions - degrademolecules to create smaller molecules and energy • Anabolic reactions - synthesize molecules for cell maintenance, growth and reproduction Chapter 10

  2. Fig 10.1 Anabolism and catabolism Chapter 10

  3. Common themes of organisms 1. Organisms or cells maintain specific internal concentrations of inorganic ions, metabolites and enzymes 2. Organisms extract energy from external sources to drive energy-consuming reactions 3. Organisms grow and reproduce according to instructions encoded in the genetic material 4. Organisms respond to environmental influences 5. Cells are not static, and cell components are continually synthesized and degraded (i.e. undergo turnover) Chapter 10

  4. Fig 10.2 Forms of metabolic pathways Linear Cyclic Chapter 10

  5. Metabolic Pathways Are Regulated • Metabolism is highlyregulated to permit organisms to respond to changing conditions • Most pathways are irreversible • Flux - flow of material through a metabolic pathway. Flux depends upon: (1) Supply of substrates (2) Removal of products (3) Pathway enzyme activities Chapter 10

  6. Feedback inhibition • Product of a pathway controls the rate of its own synthesis by inhibiting an early step (usually the first “committed” step (unique to the pathway) Chapter 10

  7. Feed-forward activation • Metabolite early in the pathway activates an enzyme further down the pathway Chapter 10

  8. Major Pathways in Cells • Metabolic fuels • Three major nutrients consumed by mammals: • (1) Carbohydrates - provide energy(2) Proteins - provide amino acids for protein synthesis and some energy(3) Fats - triacylglycerols provide energy and also lipids for membrane synthesis Chapter 10

  9. Fig 10.5 • Overview of catabolic pathways Chapter 10

  10. Catabolism produces compounds for energy utilization • Three types of compounds are produced that mediate the release of energy • (1) Acetyl CoA (2 carbon units for metabolism) • (2) Nucleoside triphosphates (ATP or GTP) • (3) Reduced coenzymes (NADH, FADH2, QH2) Chapter 10

  11. The Free Energy of ATP • Energy from oxidation of metabolic fuels is largely recovered in the form of ATP Chapter 10

  12. Fig 10.7 • Hydrolysis of ATP Chapter 10

  13. ATP is an “energy-rich” compound • A large amount of energy is released in the hydrolysis of the phosphoanhydridebonds of ATP (and UTP, GTP, CTP) • All nucleoside phosphates have nearly equal standard free energies of hydrolysis Chapter 10

  14. Energy source of phosphoanhydrides (1) Electrostaticrepulsion among negatively charged oxygens of phosphoanhydrides of ATP (2) Solvationofproducts (ADP and Pi) or (AMP and PPi) is better than solvation of reactant ATP (3) Productsaremorestablethanreactants There are more delocalized electrons on ADP, Pi or AMP, PPi than on ATP Chapter 10

  15. Enzymatic reactions often require ATP energy to drive reactions Chapter 10

  16. Amino acids, monosaccharides and lipids are oxidized in the catabolic pathways • Oxidizing agent - accepts electrons, is reduced • Reducing agent - loses electrons, is oxidized • Oxidation of one molecule must be coupled with the reduction of another molecule • Ared + Box Aox + Bred Reduced Coenzymes Conserve Energy from Biological Oxidations Chapter 10

  17. Fig 10.1 Anabolism and catabolism Glucose ATP CO2 Chapter 10

  18. Fig 11.1 • Catabolism of glucose via glycolysis and the citric acid cycle NADH NADH, FADH2 Chapter 10

  19. Table 11.1 Chapter 10

  20. Fig 10.5 • Overview of catabolic pathways READ CHAPTER 11 Chapter 10

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