Methanogenesis Flashcards
Methanogenesis
methane synthesis
Is methanogenesis aerobic or anaeorbic
Strictly anaerobic process
NO oxygen
Rumen methanogens in cows are so active a cow can belch how much methane
belch 200-400 L of methane/day!
methanogenesis in Euryarchaeota
Generate methane from H2 and CO2 or short-chain organic compounds (ex. formate, acetate, methanol )
Fermentation products from other organisms
methanogenesis in Bathyarchaeota
Encode all methanogenic enzymes and cofactors
Practical importance of methanogenesis
Energy source (produce methane (CH4) from organic waste)
environmental problem of methanogenesis
Methane is potent greenhouse gas
Absorbs infrared radiation (promotes global warming)
6 steps of the methanogenesis process
1) CO2 reduced to formate
2) Formyl group transferred to H4MPT and dehydrated
3) Dehydrated formyl group (=HC-) reduced to methyl level (-CH3) in two-step process
4) Methyl group transferred to coenzyme M (CoM)
5) Methyl group reduced to methane (CH4)
6) Regeneration of two coenzymes
6 steps of the methanogenesis process
figure 20.14
1) CO2 reduced to formate
2) Formyl group transferred to H4MPT and dehydrated
3) Dehydrated formyl group (=HC-) reduced to methyl level (-CH3) in two-step process
4) Methyl group transferred to coenzyme M (CoM)
5) Methyl group reduced to methane (CH4)
6) Regeneration of two coenzymes
What is used in methanogenesis when Formyl group transferred to H4MPT and dehydrated
H4MPT = tetrahydromethanopterin (One carbon carrier)
What happens in methanogenesis when Methyl group transferred to coenzyme M (CoM)
Na+ translocates across membrane
Generates sodium motive force to drive ATP synthase
What happens when Methyl group reduced to methane (CH4) in methanogenesis
Catalyzed by F430-containing methyl-coenzyme M reductase (MCR)
H2 = electron donor; 2 H+ released
Products: Methane and disulfide of the two cofactors (CoM-S-S-CoB)
What helps regeneration of two coenzymes in last step of methanogenesis
Heterodisulfide reductase oxidizes CoM-S-S-CoB and reduces ferredoxin
Archaeons are not known to incorporate (fix) carbon dioxide.
false
Methanogens may contribute to the greenhouse effect and global warming due to methane production.
True
Methanogens can live only in \_\_\_\_\_\_\_\_ environments. A) aerobic B) anaerobic C) microaerophilic D) All of the choices are correct.
B) anaerobic
Methanogenic Archaea are ________.
A) obligate anaerobes that produce methane
B) obligate anaerobes that consume methane
C) obligate aerobes that produce methane
D) obligate aerobes that consume methane
A) obligate anaerobes that produce methane
Methanogens link ATP synthesis to methanogenesis by ________.
A) substrate-level phosphorylation
B) the reverse TCA cycle
C) the use of bacteriorhodopsin
D) electron transport to generate proton motive force
D) electron transport to generate proton motive force
Which of the following is currently the largest group of cultured Archaea? A) Extreme halophiles B) Methanogens C) Extreme thermophiles D) Sulfate reducers
B) Methanogens
Substrates used by methanogens include H2 and CO2 as well as short-chain organic compounds such as \_\_\_\_\_\_\_\_. A) formate B) acetate C) methanol D) All of the choices are correct.
D) All of the choices are correct.
Autotrophy has been observed among the \_\_\_\_\_\_\_\_. A) methanogens B) extreme thermophiles C) cyanobacteria D) All of the choices are correct.
D) All of the choices are correct.
Which of the following do methanogens not use to form methane? A) Carbon dioxide B) Formate C) Acetate D) Phosphate
Phosphate
Some methanogenic Archaea are capable of fixing nitrogen.
True
