This document provides an overview of microbial metabolism. It discusses the two types of metabolism - anabolism and catabolism. Anabolism involves building complex molecules from simple ones and requires energy, while catabolism breaks down complex molecules into simple ones and generates energy. Key metabolic pathways like glycolysis, the tricarboxylic acid cycle, and the electron transport chain are described. Aerobic respiration and fermentation are compared in terms of the pathways and molecules involved as well as ATP yield. Control mechanisms of enzyme activity like feedback inhibition and induction are also summarized.

1. PowerPoint to accompany
Foundations in Microbiology
Fifth Edition
Talaro
Chapter
8
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Microbial Metabolism: The Chemical
Crossroads of Life
Chapter 8

3. Metabolism
The sum total of all chemical
reactions & physical workings
occurring in a cell

4. 2 types of metabolism
• Anabolism - biosynthesis
– building complex molecules from simple ones
– requires energy (ATP)
• Catabolism - degradation
– breaking down complex molecules into simple
ones
– generates energy (ATP)
4

5. 5

6. 6

7. 7

8. Enzyme structure
• Simple enzymes – consist of protein alone
• Conjugated enzymes or holoenzymes –
contain protein and nonprotein molecules
– apoenzyme –protein portion
– cofactors – nonprotein portion
• metallic cofactors – iron, copper, magnesium
• coenzymes -organic molecules - vitamins
8

9. 9

10. Enzyme-substrate interactions
10

11. • Exoenzymes – transported extracellularly,
where they break down large food
molecules or harmful chemicals; cellulase,
amylase, penicillinase
• Endoenzymes – retained intracellularly &
function there
11

12. 12

13. • Constitutive enzymes – always present,
always produced in equal amounts or at
equal rates, regardless of amount of
substrate; enzymes involved in glucose
metabolism
• Induced enzymes – not constantly present,
produced only when substrate is present,
prevents cell from wasting resources
13

14. 14

15. • Synthesis or condensation reactions –
anabolic reactions to form covalent bonds
between smaller substrate molecules,
require ATP, release one molecule of water
for each bond
• Hydrolysis reactions– catabolic reactions
that break down substrates into small
molecules, requires the input of water
15

16. 16

17. Transfer reactions by enzymes
1. Oxidation-reduction reactions – transfer of
electrons
2. Aminotransferases – convert one type of amino
acid to another by transferring an amino group
3. Phosphotransferases – transfer phosphate groups,
involved in energy transfer
4. Methyltransferases – move methyl groups from
one molecule to another
5. Decarboxylases – remove carbon dioxide from
organic acids
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18. Metabolic pathways
18

19. Control of enzyme activity
1. Competitive inhibition – substance that
resembles normal substrate competes with
substrate for active site
2. Feedback inhibition – concentration of product at
the end of a pathway blocks the action of a key
enzyme
3. Feedback repression – inhibits at the genetic
level by controlling synthesis of key enzymes
4. Enzyme induction – enzymes are made only
when suitable substrates are present
19

20. Competitive inhibition
20

21. Energy –capacity to do work or
cause change
• Endergonic reactions – consume energy
• Exergonic reactions – release energy
21

22. Redox reactions
• always occur in pairs
• There is an electron donor and electron
acceptor which constitute a redox pair
• The process salvages electrons & their
energy.
• released energy can be captured to
phosphorylate ADP or another compound
22

23. Electron carriers
• resemble shuttles that are loaded and
unloaded with electrons and hydrogen
• most carriers are coenzymes, NAD, FAD,
NADP, coenzyme A & compounds of the
respiratory chain
23

24. NAD reduction
24

25. Electron carriers
25

26. ATP
• 3 part molecule consisting of
– adenine – a nitrogenous base
– ribose – a 5-carbon sugar
– 3 phosphate groups
• Removal of the terminal phosphate releases
energy
26

27. ATP
27

28. Phosphorylation of glucose by
ATP
28

29. Formation of ATP
1. substrate-level phosphorylation
2. oxidative phosphorylation
3. photophosphorylation
29

30. substrate-level phosphorylation
30

31. Catabolism of glucose
1. Glycolysis
2. Tricarboxylic acid cycle, Kreb’s cycle
3. Respiratory chain, electron transport
31

32. Metabolic strategies
Pathways Final e-
involved acceptor ATP yield
Aerobic Glycolysis, O2 38
respiration TCA, ET
Anaerobic Glycolysis, NO3-, So4-2, variable
respiration TCA, ET CO3-3
Fermentation Glycolysis Organic 2
molecules
32

33. Overview of aerobic respiration
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34. Overview of aerobic respiration
• Glycolysis – glucose (6C) is oxidized and
split into 2 molecules of pyruvic acid (3C)
• TCA – processes pyruvic acid and
generates 3 CO2 molecules
• Electron transport chain – accepts electrons
NADH & FADH, generates energy through
sequential redox reactions called oxidative
phosphorylation
34

35. Glycolysis
35

36. TCA cycle
36

37. Electron transport system
37

38. Chemiosmosis
38

39. Fermentation
• Incomplete oxidation of glucose or other
carbohydrates in the absence of oxygen
• Uses organic compounds as terminal electron
acceptors
• Yields a small amount of ATP
• Production of ethyl alcohol by yeasts acting on
glucose
• Formation of acid, gas & other products by the
action of various bacteria on pyruvic acid
39

40. Fermentation
40

41. Products of fermentation
41

42. • Many pathways of metabolism are bi-directional
or amphibolic
• Metabolites can serve as building blocks or
sources of energy
– Pyruvic acid can be converted into amino acids through
amination
– Amino acids can be converted into energy sources
through deamination
– Glyceraldehyde-3-phosphate can be converted into
precursors for amino acids, carbohydrates and fats
42

43. 43

44. 44