1. 5
Microbial Metabolism

2. Microbial Metabolism
Metabolism: The sum of the chemical reactions in an organism
Catabolism: The energy-releasing processes
Anabolism: The energy-using processes

3. Microbial Metabolism
Catabolism provides the building blocks and energy for anabolism.
Figure 5.1

4. Metabolic pathways are determined by enzymes.
A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell.
Metabolic pathways are determined by enzymes.
Enzymes are encoded by genes.
PLAY
Animation: Metabolic Pathways (Overview)

5. The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide.
Activation energy is needed to disrupt electronic configurations.
Reaction rate is the 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
Figure 5.2

7. Enzymes Biological catalysts
Specific for a chemical reaction; not used up in that reaction
Apoenzyme: Protein
Cofactor: Nonprotein component
Coenzyme: Organic cofactor
Holoenzyme: Apoenzyme plus cofactor

8. Enzymes
Figure 5.3

9. Important Coenzymes
NAD+
NADP+
FAD
Coenzyme A

10. Enzymes
The turnover number is generally 1-10,000 molecules per second.
PLAY
Animation: Enzyme–Substrate Interactions
Figure 5.4

11. Enzyme Classification
Oxidoreductase: Oxidation-reduction reactions
Transferase: Transfer functional groups
Hydrolase: Hydrolysis
Lyase: Removal of atoms without hydrolysis
Isomerase: Rearrangement of atoms
Ligase: Joining of molecules, uses ATP

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

13. Factors Influencing Enzyme Activity
Temperature
Figure 5.5a

14. Factors Influencing Enzyme ActivitypH
Figure 5.5b

15. Factors Influencing Enzyme Activity
Substrate concentration
Figure 5.5c

16. Factors Influencing Enzyme Activity
Competitive inhibition
Figure 5.7a–b

17. Factors Influencing Enzyme Activity

18. Factors Influencing Enzyme Activity
Noncompetitive inhibition
Figure 5.7a, c

19. Factors Influencing Enzyme Activity
Feedback inhibition
Figure 5.8

20. Ribozymes
RNA that cuts and splices RNA

21. Oxidation-Reduction Oxidation is the removal of electrons.
Reduction is the gain of electrons.
Redox reaction is an oxidation reaction paired with a reduction reaction.
Figure 5.9

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

23. The Generation of ATP
ATP is generated by the phosphorylation of ADP.

24. The Generation of ATP
Substrate-level phosphorylation is the transfer of a high-energy PO4– to ADP.

25. The Generation of ATP
Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.

26. The Generation of ATP
Light causes chlorophyll to give up electrons. Energy released from the transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP.

27. Metabolic Pathways

28. Carbohydrate Catabolism
The breakdown of carbohydrates to release energy
Glycolysis
Krebs cycle
Electron transport chain

29. Glycolysis
The oxidation of glucose to pyruvic acid produces ATP and NADH.
Figure 5.11, step 1

30. Preparatory Stage Two ATPs are used
Glucose is split to form two Glucose-3-phosphate 1 3 4 5
Figure 5.12, step 1

31. Energy-Conserving Stage
Two Glucose-3-phosphate oxidized to two Pyruvic acid
Four ATP produced
Two NADH produced 9
Figure 5.12, step 2

32. Glycolysis
Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+  2 pyruvic acid + 4 ATP + 2 NADH + 2H+
PLAY
Animation: Glycolysis

33. Alternatives to Glycolysis
Pentose phosphate pathway
Uses pentoses and NADPH
Operates with glycolysis
Entner-Doudoroff pathway
Produces NADPH and ATP
Does not involve glycolysis
Pseudomonas, Rhizobium, Agrobacterium

34. Cellular Respiration
Oxidation of molecules liberates electrons for an electron transport chain.
ATP is generated by oxidative phosphorylation.

35. Intermediate Step
Pyruvic acid (from glycolysis) is oxidized and decarboyxlated.
Figure 5.13 (1 of 2)

36. Krebs Cycle Oxidation of acetyl CoA produces NADH and FADH2. PLAY
Animation: Krebs Cycle

37. Krebs Cycle
Figure 5.13 (2 of 2)

38. The Electron Transport Chain
A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain.
Energy released can be used to produce ATP by chemiosmosis.
PLAY
Animation: Electron Transport Chains and Chemiosmosis

39. Figure 5.11

40. Chemiosmosis
Figure 5.16

41. Chemiosmosis
Figure 5.15

42. Respiration
Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).
Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operations under anaerobic conditions.

43. Anaerobic Respiration
Electron acceptor
Products
NO3–
NO2–, N2 + H2O
SO4–
H2S + H2O
CO32 –
CH4 + H2O

44. Pathway
Eukaryote
Prokaryote
Glycolysis
Cytoplasm
Intermediate step
Krebs cycle
Mitochondrial matrix
ETC
Mitochondrial inner membrane
Plasma membrane

45. Energy produced from complete oxidation of one glucose using aerobic respiration.
Pathway
ATP produced
NADH produced
FADH2 produced
Glycolysis 2
Intermediate step
Krebs cycle 6
Total 4 10

46. By substrate-level phosphorylation By oxidative phosphorylation
ATP produced from complete oxidation of one glucose using aerobic respiration.
36 ATPs are produced in eukaryotes.
Pathway
By substrate-level phosphorylation
By oxidative phosphorylation
From NADH
From FADH
Glycolysis 2 6
Intermediate step
Krebs cycle 18 4
Total 30