1. An Introduction to Microbial Metabolism Chapter 8

2. energy The capacity to do work or cause change
Kinetic energy is actively performing work, Potential energy is stored (ability to perform work based on location/arrangement)
1st law of thermodynamics – energy conservation
Endergonic reactions – consume energy
Exergonic reactions – release energy

3. Endergonic:
X + Y + energy  Z
Exergonic:
X + Y  Z + energy

4. Energy conversions
Cell takes PE of chemicals (in electrons/bonds) and eventually converts them to cellular work (KE)
Endergonic/exergonic reactions are usually coupled so that the energy can either be used immediately or stored (ATP) for later use

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

7. 2 types of metabolism _________________ - biosynthesis
building complex molecules from simple ones
requires energy (ATP) - endergonic
_________________ - degradation
breaking down complex molecules into simple ones
generates energy (stored as ATP) - exergonic
Example - glycolysis

9. Enzymes Needed to keep pace (speed up reactions)
Reaction involves either breaking a molecule apart or brining one together
Catalyze reactions without becoming products or being consumed in the reaction
Act upon ______________ to form _________________
Lower _________________ so reaction rate increases

13. Enzyme-substrate interactions – lock and key fit
Active site
“Induced fit”

14. 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

17. How enzymes work: example - sucrase

18. Role of coenzyme:
Transfer functional group from one substrate to another

19. Control of enzyme activity
_________________ inhibition – substance that resembles normal substrate competes with substrate for active site
_________________ inhibition – enzymes are regulated by the binding of molecules other than the substrate on the active site
Enzyme _____________– inhibits at the genetic level by controlling synthesis of key enzymes
Enzyme _____________– enzymes are made only when suitable substrates are present

21. Enzyme repression

22. Enzyme induction

23. Things that affect enzymes
Temperature, pH, pressure
Enzymes have optimal T and pH for activity
Can be denatured by extreme temperatures or pH (changes protein structure)

25. Roles of enzymes: Pathogenesis
Produced by pathogenic microbes--make microbe a better pathogen (evade host response, destroy host tissues)
Examples:
Hemolytic enzymes (hemolysins)
Elastase, collagenase (destroy connective tissue)
Lecithinase C (destroys cells)
Penicillinase (inactivates penicillin – antibiotic resistance)
Note: names end in -________

26. Types of enzymes (location, quantity)
_______enzymes – transported extracellularly, where they break down large food molecules or harmful chemicals; cellulase, amylase, penicillinase
________enzymes – retained intracellularly & function there
_________________– always present regardless of substrate concentration (glycolysis enzymes)
_________________– produced in presence of substrate, prevents cell from wasting resources

27. Figure 8.6 Types of enzymes27 27

28. Figure 8.7 Constitutive and regulated enzymes28 28

29. Types of reactions catalyzed by enzymes
Synthesis or _________________ reactions – _________________ reactions to form covalent bonds between smaller substrate molecules, require ATP, release one molecule of water for each bond
_________________ reactions– _________________ reactions that break down substrates into small molecules, requires the input of water

30. Figure 8.8 Enzyme-catalyzed synthesis and hydrolysis reactions30

31. Transfer reactions by enzymes
Aminotransferases – convert one type of amino acid to another by transferring an amino group
Phosphotransferases – transfer phosphate groups, involved in energy transfer
Methyltransferases – move methyl groups from one molecule to another
Decarboxylases – remove carbon dioxide from organic acids
Oxidation-reduction (redox)reactions – transfer of electrons (may involve _________________ )

32. REDOX reactions
The process by which electrons are transferred between atoms is called an oxidation/reduction reaction (redox) – we can track movement of e- by following H transfers
_________________ = loses e- (donor becomes oxidized; reducing agent)
_________________ = gains e- (acceptor becomes reduced; oxidizing agent)
Occurs as a paired reaction
“LEO says GER” or “OIL RIG”

33. Cellular respiration is one big redox reaction!
Redox reactions involve electron transfers
O I L R I G
(Oxidation is Losing; Reduction is Gaining)

34. Redox reactions Involve electron transfers (energy transfers)
always occur in pairs
electron donor + electron acceptor = redox pair
process salvages electrons & their energy.
released energy can be captured to _________________ ADP or another compound

35. Electron donor + Electron acceptor
Redox reactions
Electron donor + Electron acceptor
NOTE: electron transfers involve a hydrogen atom (proton + electron)
= ____________________ and involves an electron carrier

36. REMEMBER: Cellular respiration is one big _________________ !

37. Metabolic Pathways 37 37

38. Electron carriers
Redox reactions
resemble __________ that are loaded and unloaded with electrons and hydrogen
most carriers are __________, NAD, FAD, NADP, coenzyme A & compounds of the respiratory chain
donor
shuttle
acceptor

39. NAD reduction (carries 2 e- )
Redox reactions

40. Electron carriers – coupled reaction

41. Overview of cell respiration – electrons are removed from glucose and eventually used to make ATP
_____________________________

42. NADH
1/2
The path that electrons take on their way down from glucose to oxygen involves many stops
(from food via NADH)
Energy for
synthesis of
2 H
2 e
Electron transport chain
2 e
1/2
2 H
Figure 6.6

43. ATP – the energy shuttle
3 part molecule consisting of
adenine – a nitrogenous base
ribose – a 5-carbon sugar
3 phosphate groups
_________________ _________________ _________________

44. _____________ of glucose by ATP
How does ATP “give” energy?
ATP transfers energy to compounds that are going to be catabolized (or going to do work) by donating the high energy phosphate
_____________ of glucose by ATP

45. How is ATP regenerated? ATP used for Energy must be regenerated (ADP + Pi)
substrate-level phosphorylation
oxidative phosphorylation
photophosphorylation

46. 1. substrate-level phosphorylation

47. Other ways of making ATP
2. Oxidative phosphorylation: Used by aerobes. series of redox reactions (electron transport system). Involves chemiosmosis.
3. Photophosphorylation – used in photosynthetic organsims. Driven by sunlight (series of reactions).