1. Ch 5 Microbial Metabolism

2. Student Learning Outcomes:
Differentiate between, anabolism, and catabolism.
Identify the components of an enzyme and describe the mechanism of enzymatic action.
List the factors that influence enzymatic activity.
Explain what is meant by oxidation–reduction.
Describe the chemical reactions of glycolysis.
Explain the products of the Krebs cycle.
Describe the chemiosmotic model for ATP generation.
Compare and contrast aerobic and anaerobic respiration.
Describe the chemical reactions and some products of fermentation.
Categorize the various nutritional patterns among organisms according to energy and carbon source.

3. Catabolic and Anabolic Reactions
Metabolism: The sum of all chemical reactions in an organism
Catabolism: Provides energy and building blocks for anabolism.
Anabolism: Uses energy and building blocks to build large molecules

4. Role of ATP in Coupling Reactions
A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell. Metabolic pathways are determined by enzymes, which are encoded by genes.
Fig 5.1

5. Collision Theory
states that chemical reactions (formation or breakage of bonds) can occur when atoms, ions, and molecules collide
Activation energy is needed for most chemical reactions
Reaction rate depends on frequency of collisions with enough energy to bring about a reaction.
Reaction rate can be increased by enzymes or by increasing temperature or pressure

6. Enzymes lower Activation Energy
Compare to Fig 5.2

7. Enzymes Biological catalysts; specific; not used up in that reaction
Fig 5.3
Enzymes
Biological catalysts; specific; not used up in that reaction
Composition of Holoenzyme: Apoenzyme plus cofactor; or apoenzyme plus coenzyme (NAD+, NADP+, FAD)
Naming of enzymes (see Table 5.1): Oxidoreductases (e.g.: Lactate dehydrogenase and Cytochrome oxidase); ligases, hydrolases etc.

8. Mechanism of Enzymatic Action
Compare to Fig 5.4

9. Factors Influencing Enzyme Activity
Enzymes can be denatured by temperature and pH
Figure 5.6

10. These graphs indicate that optimum enzyme activity will occur at:
25 oC and pH 7.0.
25 oC and pH 5.0.
37 oC and pH 7.0.
37 oC and pH 5.0.
45 oC and pH 7.0.

11. Factors Influencing Enzyme Activity: Substrate concentration
Figure 5.5c

12. Noncompetitive – allosteric inhibitors Competitive inhibitorsvs
Fig 5.7

13. Sulfa drugs

14. Feedback Inhibition
Also known as end- product inhibition Controls amount of substance produced by a cell Mechanism is allosteric inhibition
Fig 5.8

15. Energy Production: Oxidation-Reduction Reactions
Redox reaction = oxidation reaction paired with reduction reaction.
Oxidation = removal of e-
Reduction = gain of e-
Fig 5.9

16. Oxidation-Reduction cont.
In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.
Fig 5.10

17. Phosphorylation: The Generation of ATP
Substrate level phosphorylation: transfer of a high-energy PO4– to ADP.
Oxidative phosphorylation: transfer of electrons from one compound to another is used to generate ATP by chemiosmosis.

18. Metabolic Pathways of Energy Production: COH Catabolism
Cellular respiration
Aerobic respiration
Anaerobic respiration
Fermentation
The three steps of aerobic respiration
Glycolysis (oxidation of _____ to ______)
Krebs cycle (oxidation of acetyl CoA to ___)
Oxidative phosphorylation (e- transport chain)

19. Glycolysis Generates small amount of ATP (how many?)
Multi – step breakdown of glucose into pyruvate
Generates
small amount of ATP (how many?)
small amount of reducing power – (?)
Alternative pathways: Pentose phosphate and Entner-Doudoroff

20. The Steps of Glycolysis
Compare to
Fig. 5.12

21. Krebs Cycle Other names?
Preparatory (Transition) step generates acetyl-CoA from pyruvate (decarboxylation)
Acetyl group of acetyl-CoA enters TCA cycle
Generates ATP and reducing power
Generates precursor metabolites

22. Krebs Cycle
Compare to Fig 5.13

23. Electron Transport Chain
Formed by series of electron carriers (cytochromes) located in ___________
Oxidation/Reduction reactions. Electron carriers (reducing power) from glycolysis and TCA cycle transfer their electrons to the electron transport chain
Generates proton gradient or proton motive force (pmf)
In chemiosmosis, pmf generates energy via oxidative phosphorylation

24. Electron Transport and the Chemiosmotic Generation of ATP
See Textbook Animations
Fig. 5.16

25. Overview of Respiration and Fermentation
Foundation Figure
Fig 5.11

26. Also review Fig 5.17

27. Anaerobic Respiration
Inorganic molecule is final electron acceptor, e.g.:
NO3-
SO42-
ATP yield lower than in aerobic respiration because only part of Krebs cycle operates under anaerobic conditions.

28. Fermentation Scientific definition:
Any spoilage of food by microorganisms (general use)
Any process that produces alcoholic beverages or acidic dairy products (general use)
Any large-scale microbial process occurring with or without air (common definition used in industry)
Scientific definition:
Uses an organic molecule as the final electron acceptor
Does not use the Krebs cycle or ETC
Energy yield low
Diversity of end products: _____________________
(see Table 5.4)

29. The Relationship of Fermentation to Glycolysis
Not in book.
However, compare to Fig 5.18

30. Location of Carbohydrate Catabolism
Pathway
Eukaryote
Prokaryote
Glycolysis
Preparatory step
Krebs cycle
ETC

31. Energy produced from complete oxidation of one glucose molecule using aerobic respiration
Pathway
ATP Produced
NADH Produced
FADH2 Produced
Glycolysis
Preparatory step
Krebs cycle
Total

32. By Substrate-Level Phosphorylation By Oxidative Phosphorylation
ATP produced from complete oxidation of one glucose using aerobic respiration
Pathway
By Substrate-Level Phosphorylation
By Oxidative Phosphorylation
From NADH
From FADH
Glycolysis
Intermediate step
Krebs cycle
Total

33. Catabolism of Other Compounds
Polysaccharides and disaccharides
Amylases for digestion of ___________ (very common)
Cellulase for digestion of __________ (only bacteria and fungi have this enzyme)
Disaccharidases
Lipid catabolism not covered

34. Protein Catabolism Protein Amino acids Organic acid
Extracellular proteases
Krebs cycle
Deamination, decarboxylation, dehydrogenation, desulfurylation
Organic acid
Decarboxylation

35. Biochemical Tests and Bacterial Identification: Fermentation Tests
Different species produce different enzymes  test detects enzyme Mannitol Fermentation:

36. Metabolic Diversity among Organisms
Energy source: Phototrophs vs. Chemotrophs
Principal carbon source: Autotrophs vs. Heterotrophs
Chemoheterotrophs use organic compound as energy source and carbon source. Most medically important bacteria.
Saprophytes vs. parasites

37. Anabolic Pathways From Photosyntheis on not covered, except for
Protein biosynthesis (see Ch 8)
Definition of chemoheterotroph
the end