Microbial Metabolic diversity Flashcards
What are organic compounds called
Heterotrophs
What are inorganic compounds called
Autotrophs
What is an inorganic source of electrons called
Litho
What is an organic source of electrons
Organo
What is catabolism
Breaking down of molecules
What is anabolism
Synthesis of molecules
Where do Phototrophs get their electrons
Use light as an energy source to reduce compounds then use these as electron donor
Where do chemolithotrophs get their electrons
Inorganic molecules
Where do Chemoorganotrophs get their electrons
Organic molecules
What are the electron acceptors
Respiration
Fermentation
What is the final electron acceptor
Oxygen
What happens as you move down the ETC
Reduction potential increases
What is energy conserved as in the electron transfer system
Transmembrane PMF which is used for ATP in ATP synthesis
When is a reaction possible
When Gibbs free energy is from low to high reduction potential
What is the eqn for Gibbs free energy
-nF(delta)E
n = number of electrons F = Faraday constant
What are the 2 energy sources that underpin metabolism
NADH, NADPH and FADH2
ATP
The energy generated during
Electron transfer generates a proton
gradient that drives ATP synthesis
What are four compounds which can be used as a source of electrons
Carbohydrates
Lipids
Peptides
Aromatic compounds
What are the 2 key metabolites produced during glucose metabolism
Acetyl-CoA
Pyruvate
What are the 3 major metabolic types
Aerobic - O2 available
Anaerobic - Alternative Electron acceptor
Fermentation - No alternative
What does electron transport occur through
Quinones and iron-sulfur proteins
Why is anoxygenic respiration important
to exploit a wide range of ecological niches
What is dentrification
The process in which nitrates are converted into oxygen
How is Acetate used in methanogensis
CH3-COO- + H+ -> CH4 + CO2
How is methanol used in methanogenesis
4CH3OH -> 3CH4 + CO2 + 2H2O
What differentiates anaeobic respiration from fermentation
Anerobic uses inorganic molecules other than O2 as an electron acceptor via a membrane bound respiratory chain
ATP produced by oxidative phosphorylation via the PMF)
Fermentation uses organic molecules as electron receptors without the ETC
ATP produced by substrate-level phosphorylation in the cytoplasm
What are key features of fermentation
Occurs under anaerobic conditions when no electron acceptor is available
ATP is NOT produced by oxidative phosphorylation but Substrate Level Phosphorylation (SLP).
Fermentation energy yields are low; cells grow more slowly than when they respire.
What is the major source of electrons in chemolithotrophs
Can extract electrons from many compounds to power metabolism
Hydrogen –> hydrogenotrophic
What are the important properties of Chemolithotrophs
Most chemolithotrophs use CO2 as a carbon source to produce organic molecules via Calvin cycle, reverse TCA cycle (reverse Krebs)
They can also use more complex molecules (acetate)
To fix carbon, they require NADH
This requires the consumption of H+ for a reverse electron flow process
What is hydrogenotrophy
Using hydrogen (H2) as an electron donor
H2 is a excellent electron donor thatcan use a wide range of acceptors
Hydrogenotrophs are can use a wide range of electron acceptors
When is oxygen seen as an electron acceptor
In the formation of Water
When is So4 2- seen as an electron receptor
In the formation of water and HS-
When is CO2 seen as an electron acceptor
In the formation of water and methane
When can iron be oxidised to Fe3+
At low pHs
When does Fe3+ become ferric hydroxide
As the pH gets lower
What is the electron acceptor in iron oxidation
Nitrates as well as oxygen
When does nitrification occur
Aerobic conditions
When does Anamox occur
Anaerobic conditions
When is sulfur oxidation used
Acid-producing microbes for biomining
Oxidize sulfide of iron and copper (FeCuS2, Cu2S)
the oxidation of Cu+ and acid production dissolves
the metal from the rocks
What photosystems are used in photsynthesis (Oxygenic)
Anoxygenic
PS1 and PS2
Br, PS1 and PS2
What is bacteriorhodopsin
An abundant light-driven proton pump in archaea membranes
Covalently attached retinal to redoxin
Upon light exposure, pigment can trigger a movement of electrons
Pulls out a proton from the structure which is replaced by the environment
The movement of protons generates a gradient used to produce ATP
What are the features of cyanobacteria
Photosynthetic, No chloroplasts, Sometimes no thylakoids, ancestor of the chloroplast
How do cyanobacteria photosynthesis
Light captured by photosystems –> channel energy to reaction center –> Contain several pigments which use at various wavelengths (chlorphyll, carotenoids and bilins)
Oxygenic pathway: light provides energy to strip e- from H2O, yielding H+, the electrons flow is used to pump protons outside the cell and reduce NADP+, the H+ gradient is used to generate ATP and the NADPH and ATP are used to fix CO2 (make glucose)
What do green sulfur bacteria used for energy
Anoxygenic photosynthesis
What is the process of anoxygenic photosynthesis
Light is captured by antenna complexes in organelles called chlorosomes, Photon energy is transferred to the PSI reaction centre
PSI donates an electron to the ETC
Electron transport pumps protons outside the cell and reduce NADP+ via ferredoxin the H+ gradient is used to generate ATP
PSI receives electrons from inorganic sulfur derivatives (H2, H2S)
How do purple bacteria photosynthesise
Anoxygenically
- Light is captured by antenna complexes in organelles called chromatophores
Same process as Green sulfur bacteria but uses cyclic ETC and Cyclic photophosphorylation. The electron flow is also reversed
- Photon energy is transferred to the PSII reaction centre
What are good electron donors
They have negative reduction potential
What is produced in anaerobic respiration
Lactic acid or ethanol and ATP molecules.
