Lecture 3: Microbial Metabolism Flashcards
…
What do we mean by metabolism?
Nutrition leading to energy generation & growth
Catabolism: breakdown of molecules into simple forms. Used for energy generation & supplying building blocks for growth. (Releases energy, some lost as heat)
Anabolism (biosynthesis): construction of complex molecules from simpler ones, energy requiring process
Growth : Anabolism
- requires energy
- breaking & forming chemical bonds releases & uses energy
Catabolism
- generally a gradual breakdown of complex structures
- electrons transferred to generate energy for the cell
- microbes can be classified bases on how they generate energy e.g. chemical reactions or light
Energy & life
- life based on carbon (& N, S, O, H, P etc.)
- energy acquisition by cells is linked to biosynthesis (but is separate)
> …..
Organisms can be described by how they obtain energy & carbon
Helps to understand:
- the role & effect organism has in habitat
- requirements needed for growth & colonisation
- ultimately how ecosystems function
Definitions:
energy
- if microbe generates energy from light: Phototroph
- if microbe generates energy from chemical rearrangement of molecules (organic or inorganic): Chemotroph
Definitions:
*growth**:
- if microbe fixes CO2 as a principal carbon source = Autotroph
- if microbe uses external sources of carbon for biosynthesis = Heterotroph
Mixotroph can do both
Definitions
….
Definitions:
Definitions:
- chemotrophs can use organic or inorganic sources
- organotroph: microbe uses chemical pathways using organic molecules to donate electrons to generate energy, (often used synonymously with CHEMOHETERTROPH)
-
Lithotroph: microbe uses chemical pathways using inorganic molecules to donate electrons to generate energy
…
…
Energy & microbial communities
- understanding metabolic processes helps understand ecosystem functions
- elements must be cycled between species to allow growth (all food webs)
- interdependence between groups of organisms key to survival
E.g. without autotrophy, heterotrophy would convert all C in biomass to CO2 in years
..
Energy & microbial communities
Microbial communities are highly competitive
- compete for resources > directly & indirectly
- survival depends on ability to utilise available resource
> niche partitioning
> ……
KEY MESSAGE
The metabolism / chemical reaction that generates the greatest amount of energy in a given environment will be favoured
…
All about energy
C6H12O6 + 6O2»_space;> 6CO2 + 6H2O
Oxidation of glucose generates energy for the cell.
…
Oxidation-reduction reactions (REDOX)
- movement of an electron from a molecule (oxidation) to another (reduction) - OIL RIG
- some redox reactions carried out by microbes:
…..
Energy defined by thermodynamic laws
- 1) in energy transformations, the total energy remains constant (i.e. energy is not created or destroyed)
- 2) in energy transformations, some energy creates a disorder (entropy) & not work (i.e. systems tend to become more disordered)
3) entropy becomes constant as temp approaches absolute 0
….
All about energy
Energy defined by thermodynamic law
Total energy of a system = Enthalpy (H)
H = G + T x S
G = free energy; T = temperature; S = entropy (disorder) = unusable energy
Gibbs Free Energy Change, ΔG
ΔG = ΔH - TΔS
ΔH = heat transfer released or absorbed (enthalpy)
ΔS = measure of disorder (change in entropy)
T = temp
….
Gibbs Free Energy Change, ΔG
…
