5-4: Chemolithotrophs & Phototrophs Flashcards
What is a chemolithotroph
Get energy from oxidizing inorganic molecule (minerals)
Where are chemolithotrophs found
Anywhere with a source of reduced inorganic compounds
Common electron donors (energy sources) of chemolithotrophs
H2S, H2, Fe2+, NH4
Example of chemolithotrophic microbe
Ralstonia eutropha
Information about Ralstonia eutropha
G (-) in soil, freshwater
Chemolithotroph using H2, CO2, O2
Has two hydrogenase enzymes
What do the hydrogenase enzymes in Ralstonia eutropha do
Split H2 to H+ and donate electrons to produce ATP/NADH
Membrane bound enzyme donates e to quinones in ETC = proton motive force/ATP
Soluble enzyme reduces NAD+ to NADH =reducing power
In phototrophs, ATP is generated by …
Photophosphorylation
What are oxygenic phototrophs? E.g.?
Generate O2 as a biproduct of photosynthesis
e.g. cyanobacteria
What is a phototroph that does not generate O2? Eg?
Anoxygenic phototroph
e.g. green sulfur bacteria
What are antenna pigments in phototrophs
Light-harvesting complexes that capture light energy and transfer to a reaction center
Oxygenic = chlorophylls
Anoxygenic = bacteriochlorophylls
What are photosynthetic reaction centers
Complexes of proteins and pigments where electrons are excited and transferred to ETC
How many bacteriochlorophylls are there? Why are there different ones?
Many, each with different pigmentations/absorption ranges allowing different phototrophs to coexist in same habitat (use different light)
Purple bacteria are what kind of phototroph
Anoxygenic
Photosynthetic reaction center of purple bacteria contains a
Bacteriochlorphyll (P870)
Describe the ETC of purple bacteria
P870 absorbs light E, which goes from weak e donor P870 to strong e donor P870*, which donates e to quinone, enters ETC. ATP synthase makes ATP
Electrons from purple bacteria cycle back to P870 and return it to its original state, this is called
Cyclic photophosphorylation
What is a Q-type reaction center? eg?
Electrons transferred to a quinone
e.g. purple bacteria
If an autotroph lacks an electron donor with a more negative reduction potential than NAD+/NADH how do they generate reducing power
Reverse electron transport - proton motive force used to drive e in opposite direction of ETC = reduce NAD to NADH (takes a lot of E)
The two photocenters of oxygenic phototrophs
Photosystem 1 (PSI, P700, FeS-type)
Photosystem 2 (PSII, P680, Q-type)
What do the chloroplasts thylakoid membranes contain
Photosynthetic reaction centers
who uses the calvin cycle
phototrophic bacteria, chemolithotrophic bacteria, algae, some arachae
What does the calvin cycle do
Fix CO2, convert it to organic molecules
Costs ATP and NADH
Enzyme for carboxylation step in calvin cycle?
RuBisCO
How many carbons go into the calvin cycle, how many are drawn off for biosynthesis
36C in, 6C
Draw out slide 15**
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