what are the processes of organotrophic metabolism
- aerobic respiration
- anaerobic respiration
- fermentation
what is organotrophic metabolism
- a wide diversity of substrates are used by organotrophs to conserve energy
- glycolytic pathways and the TCA cycle
what is glycolysis
- variants of the pathway exist depending on the carbohydrate substrate and the needs of the organism -> EM, ED, PPP
- (ATP) energy is invested early in the pathway to synthesize low energy phosphate molecules so that more energy can be obtained later
- different yields of energy conserved and reducing power depending on the variant
what is the TCA cycle
- Key Pathway for Energy conservation, Generation of reducing power and synthesis of precursors in most respiring organotrophs
- provides important precursors for anabolism
- NADH/FADH2 is used to produce additional ATP using the electron transport change during aerobic and anaerobic respiration
what are some precursors produced by TCA cycle
- acetyl-CoA produces fatty acids, lipids
- oxaloacetate produces amino acids, nucleotides
- succinyl-CoA produces porphyrins, heme group
- alpha ketoglutarate produces glutamate, glutamine, other amino acids
what is fermentation
- does not involve the use of a terminal electron acceptor
-> no ETC
-> does not use TCA cycle for production of NADH - some organisms are obligate fermenters (Clostridium spp.)and some ferment in the absence of terminal electron acceptors (E.coli)
what is the major challenge for fermenters and the solution
- major challenge for fermenters is achieving redox balance
-> they must get rid of the electrons from the oxidation of organic matter (need to reoxidize NADH to NAD+) -> TEA plays this role in respiration - solution = an endogenous electron acceptor is typically used (product of their metabolism)
what are the requirements of fermentation and the process
- conserve energy
- reoxidize NADH
process:
1. uptake of organic compound
2. produce energy rich compound
3. undergo substrate level phosphorylation to produce oxidized compound
4. fermentation of product and regeneration of NAD+ by donating electron from NADH to oxidized compound
What are the fundamental differences between fermentation and respiration
fermentation:
- no external electron acceptor is used
- organic compounds act as both electron acceptor and donor
- ATP is typically generated by substrate level phosphorylation
- often named after the main products formed
ex. butanediol fermentation, homolactic fermentation
respiration :
- external electron acceptors are used
- ATP is generated by oxidative phosphorylation (role of electron transport chain and proton motive force)
- often named after the electron acceptor or main product used
ex. aerobic respiration, sulfate reduction
what are some other chemoorganotrophic substrates
- carbohydrates
- lipids
- proteins
- amino acids
- nucleotides
- hydrocarbons including methane, pesticides, Pharmaceuticals, cellulose
-> biotechnological potential (hydrocarbon degrading marine bacteria)
what is methane oxidation
- methanotrophs oxidize methane to CO2
- oxygen is the terminal electron acceptor
- key enzyme = methane monooxygenase (MMO)
- formaldehyde can be oxidized completely to CO2 or used in biosynthesis
- due to structure of electron transport chain they can only take in methane not glucose
- electron transport generates proton motive force
