Methanogenesis

Question 1

Methanogenesis

Answer 1

methane synthesis

Question 2

Is methanogenesis aerobic or anaeorbic

Answer 2

Strictly anaerobic process

NO oxygen

Question 3

Rumen methanogens in cows are so active a cow can belch how much methane

Answer 3

belch 200-400 L of methane/day!

Question 4

methanogenesis in Euryarchaeota

Answer 4

Generate methane from H2 and CO2 or short-chain organic compounds (ex. formate, acetate, methanol )
Fermentation products from other organisms

Question 5

methanogenesis in Bathyarchaeota

Answer 5

Encode all methanogenic enzymes and cofactors

Question 6

Practical importance of methanogenesis

Answer 6

Energy source (produce methane (CH4) from organic waste)

Question 7

environmental problem of methanogenesis

Answer 7

Methane is potent greenhouse gas

Absorbs infrared radiation (promotes global warming)

Question 8

6 steps of the methanogenesis process

Answer 8

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

Question 9

6 steps of the methanogenesis process

figure 20.14

Answer 9

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

Question 10

What is used in methanogenesis when Formyl group transferred to H4MPT and dehydrated

Answer 10

H4MPT = tetrahydromethanopterin (One carbon carrier)

Question 11

What happens in methanogenesis when Methyl group transferred to coenzyme M (CoM)

Answer 11

Na+ translocates across membrane

Generates sodium motive force to drive ATP synthase

Question 12

What happens when Methyl group reduced to methane (CH4) in methanogenesis

Answer 12

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)

Question 13

What helps regeneration of two coenzymes in last step of methanogenesis

Answer 13

Heterodisulfide reductase oxidizes CoM-S-S-CoB and reduces ferredoxin

Question 14

Archaeons are not known to incorporate (fix) carbon dioxide.

Answer 14

false

Question 15

Methanogens may contribute to the greenhouse effect and global warming due to methane production.

Answer 15

True

Question 16

Methanogens can live only in \_\_\_\_\_\_\_\_ environments.
A) aerobic
B) anaerobic
C) microaerophilic
D) All of the choices are correct.

Answer 16

B) anaerobic

Question 17

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

Answer 17

A) obligate anaerobes that produce methane

Question 18

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

Answer 18

D) electron transport to generate proton motive force

Question 19

Which of the following is currently the largest group of cultured Archaea?
A) Extreme halophiles
B) Methanogens
C) Extreme thermophiles
D) Sulfate reducers

Answer 19

B) Methanogens

Question 20

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.

Answer 20

D) All of the choices are correct.

Question 21

Autotrophy has been observed among the \_\_\_\_\_\_\_\_.
A) methanogens
B) extreme thermophiles
C) cyanobacteria
D) All of the choices are correct.

Answer 21

D) All of the choices are correct.

Question 22

Which of the following do methanogens not use to form methane?
A) Carbon dioxide
B) Formate
C) Acetate
D) Phosphate

Answer 22

Phosphate

Question 23

Some methanogenic Archaea are capable of fixing nitrogen.

Answer 23

True