1. ESSENTIAL CONCEPTS OF METABOLISM
CHAPTER 5

2. Metabolism Anabolism Small molecules joined by bonds Energy required
Catabolism
Bonds broken,
Energy released

3. Microbial Metabolism Autotrophy versus heterotrophy
Chemo- versus Photo-

4. Energy Capture
Electron Transfer
Redox Reactions

5. Enzymes Control Metabolic Pathways
Proteins
Catalysts
Activation Energy lowered
Apoenzyme
Holoenzyme
Active Site

6. Apoenzyme versus Holoenzyme
Coenzyme
Cofactor
Holoenzyme

7. Enzyme/Substrate Complex – a highly specific binding event which allows new product(s) to be formed.

8. Enzyme Inhibition
Competitive

9. Enzyme Inhibition
Noncompetitive
Allosteric site
Feedback Inhibition

10. Reaction Rate Influences
Temperature pH

11. Effect of Enzyme Concentration

12. Effect of Substrate Concentration
Product Concentration – Often a regulatory role

13. Carbohydrate Catabolism
Universal First Step – Glycolysis Pathway
Overall reaction:
Glucose + 2 ATP + 2ADP + 2 Pi + 2 NAD Pyruvate + 4 ATP + 2NADH*
Low Energy Yield in terms of ATP (2 ATP)
*NADH molecules carry large quantities of energy
Not always available to the cell

14. Glycolytic Pathway Each step is a separate enzymatic reaction

15. High Energy Electron-Carrying Coenzymes
Nicotinamide Adenine Dinucleotide
NAD+ + H+ + 2e– NADH
Flavin Adenine Dinucleotide
FAD + 2H+ + 2e– FADH2

16. Fermentation Follows Glycolysis in some microbes Anaerobic process
Substrate : 2 Pyruvate molecules per glucose
End products of reduction:
Acids (Lactobacillus)
Alcohols (Saccharomyces)
Re-oxidizes 2 NADH to allow NAD+ usage in glycolysis
No ATP created during fermentation

17. Acid/Alcohol Fermentation Pathways

18. Aerobic Respiration
Alternative to Fermentation possessed by some microbes
Aerobic process
2 Pathways combined
Krebs Cycle
Electron Transport Chain

19. Krebs Cycle Needs Acetyl Coenzyme A
Preparatory Step:
2 Pyruvate + 2 NAD+ + 2 CoenzymeA CO Acetyl CoA + 2 NADH

20. Krebs Cycle Pathway
Krebs Cycle oxidizes remaining organic carbon molecules to CO2
Oxidative Phosphorylation (Electron Transport Chain) harnesses the energy within reduced NADH and FADH2
Allows extraction of energy from NADH and other high energy electron carriers

21. Krebs Cycle Oxidation Substrates:
2 Acetyl CoA per original glucose molecule
2 GDP (ADP equivalents)
6 NAD+
2 FAD
Products:
4 CO2
2 GTP (ATP equivalents)
6 NADH
2 FADH2

22. Electron Transport Chain
Redox
Electrons from NADH and FADH2
Electron Carriers
Flavoproteins
Cytochromes
Ubiquinones
Terminal electron Acceptor
Oxygen atom
Reduced to water

23. Electron Transport Chain (ETC) Energy Yields

24. Electron Transport Chain - Molecular Events

25. Chemiosmosis

26. Energy Yields Glycolysis: 2 ATP Substrate level phosphorylation
Krebs Cycle: 2 ATP
Electron Transport Chain: 34 ATP
10 NADH yield 30 ATP
2 FADH2 yield 4 ATP
Oxidative phosphorylation
Aerobic Respiration total: 36 ATP
Glycolysis + Aerobic Respiration total: 38 ATP

28. Anaerobic Respiration
Respiration Pathway (Krebs Cycle + ETC) using inorganic terminal e– acceptors other than O2
Energy yield is less than Aerobic Respiration but greater than fermentation

29. Fat Catabolism Glycerol Enters glycolysis Fatty Acids
Beta oxidation creates Acetyl coA
Enters the Krebs cycle

30. Protein Catabolism Protein hydrolysis Deamination NH2 group is lost
Carbon skeleton usage
Krebs cycle
Some to glycolysis

31. Photosynthesis (1)
Light dependent reactions - Photophosphorylation

32. Photosynthesis (2) Light independent reactions Carbon fixation
ATP provides energy to link carbon atoms into glucose molecules
Water conservation is an issue for many plants

33. Energy Usage Biosynthesis (Anabolism) Membrane Transport Motility
Bioluminescence