L11 - Carbon Cycling Flashcards
Why are microorganisms important for biogeochemical cycles?
they can get energy from a large variety of chemical reactions, both aerobic and anaerobic, range of metabolisms, important in cycling various nutrients (C, N, S)
What are the earth’s major carbon reservoirs?
includes atmosphere, land, oceans, sediments, rocks and biomass. larger proportion in rocks and sediment (stable) and less in labile cpomounts , fossil fuels and ocean. lots in the earth’s crust
What are some parameters in understanding the cycling of elements?
reservoir size
turnover time (speed at which carbon gets cycled)
How is CO2 transported around the cycle
- CO2 in atmosphere moves around a lot(most rapidly transferred carbon reservoir)
- CO2 is fixed through photosynthetic plants, microbes, marine CO2 fixation
- is returned to the atmosphere by organisms and use of fossil fuel reservoir
- a large proportion of CO2 released is decomposed by microbes which breaks down organic matter
Phototrophic organisms are the foundation of the carbon cycle. What are oxygenic phototrophs and How do you divide oxygenic phototrophic organisms into 2 groups?
they use CO2 to make O2
- plants dominate organisms of terrestrial environment
- microorganisms dominate aquatic environment
What is methane, how potent is it and how is it released?
CH4, per molecule more potent than CO2, major product of aerobic decomposition
What are the oxidation states of carbon in CO2 and CH4
CO2 +4, CH4 -4
What is methanogenesis and methanotrophy
Methanogenesis is the process by which certain microbes, called methanogens, produce methane gas as a byproduct in oxygen-free environments. Methanotrophy is the process by which certain bacteria use methane as their energy source, converting it into carbon dioxide.
What is the significance of methane hydrates?
- high levels of methane under high pressure and low temp
- methane trapped bottom of ocean/permafrost as methane hydrates
- can absorb and release methane gas and drives warming
- fuels deep-sea ecosystems called cold seeps
How is C and N cycle coupled?
primary production (CO2 to organic carbon)
- low organic C = low nitrogen fixation, feeds back and reduce amount for C that can be fixed
What is methanogenesis?
carbon cycling in anoxic environments. methanogens reduce CO2 to CH4 with H2 as an electron donor
What does syntrophs do?
methanogens team up with syntrophs as partners to supply them with necessary substrates (hydrogens)
What is syntrophy?
process whereby 2 or more microorganisms degrade a substance neither can degrade alone. mostly secondary fermentations. important for anoxic portion of carbon cycle.
What is syntrophy based on?
interspecies hydrogen transfer. one partner produces H2 and the other consumes the H2
How is ethanol fermentation and methanogenesis coupled? who provides the hydrogen and is gibbs positive overall?
ethanol fermentation produces the H2 and methanogenesis uses teh H2. overall gibbs is negative so spontaneous
Where else can you find methanogenesis processes?
linked to other microbial reactions where complex polymers from cells through hydrolysis. fermentation and production of acetate
Where is methanogenic archaea found?
GI tract of eukarya from mammals to protists
_______ methanogens can consume ____ generated from ____ fermentation
endosymbiotic methanogens can consume H2 generated from glucose fermentation
which releases more CH4? biotic or abiotic processes
biotic
How is methane produced by ruminants?
byproduct of digestion of plant matter. plant is hard to break down so in their body there is a compartment with microbes that aid in the breakdown of plant. they make a lot of methane during this process
What is acetogenesis? How does it relate to methanogenesis?
- H2 consuming process competing with methanogenesis in some environments
- occurs in termite hindgut
- methanogenesis is more energetically favourable
- acetogens can ferment glucose and methoxylated aromatic compounds (methanogens can’t)
- dietary supplements to favour acetogenesis so less problematic
How did LUCA fit into the chemo-autotrophic ecosystem?
photosynthesis was missing so recycling of C was photochemical without biological input
