1. 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 Catabolic reactions - degrade molecules to create smaller molecules and energy Anabolic reactions - synthesize molecules for cell maintenance, growth and reproduction

2. Fig 10.1 Anabolism and catabolism

3. Prentice Hall c2002Chapter 103 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)

4. Fig 10.2 Forms of metabolic pathways Linear Cyclic

5. Metabolic Pathways Are Regulated Metabolism is highly regulated 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

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)

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

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

9. Fig 10.5 Overview of catabolic pathways

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, FADH 2, QH 2 )

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

12. Fig 10.7 Hydrolysis of ATP

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

14. Energy source of phosphoanhydrides (1) Electrostatic repulsion among negatively charged oxygens of phosphoanhydrides of ATP (2) Solvation of products (ADP and P i ) or (AMP and PP i ) is better than solvation of reactant ATP (3) Products are more stable than reactants There are more delocalized electrons on ADP, P i or AMP, PP i than on ATP

15. Enzymatic reactions often require ATP energy to drive reactions

16. Reduced Coenzymes Conserve Energy from Biological Oxidations 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 A red + B ox A ox + B red

17. Fig 10.1 Anabolism and catabolism Glucose CO 2 ATP

18. Catabolism of glucose via glycolysis and the citric acid cycle NADH, FADH 2 NADH

19. Table 11.1

20. Fig 10.5 Overview of catabolic pathways READ CHAPTER 11