Autotrophy Flashcards
To be a true autotroph
- you have to be able to fix carbon using nonorganic sources of energy
chemotrophs
- get energy from inorganic molecules that have electrons in them.
inorganic chemicals used in autotrophy
- H2
- NH3
- H2S, S, S2O3,
- Fe2+
- H2, CO2, Formate
C. jejuni is not an autotrophic organism because
- it cannot fix carbon
mixotrophs
- microorganisms that can use an inorganic energy source but must rely on organic carbon for biomass.
pathogens
- get H2 from anaerobies
methanogens
- live in anaerobic sediments with H2 evolvers
nitrogen fixers
- H2 is an oblique byproduct of N2 fixation
Nitrosomas
a chemolitotroph that gets energy from the oxidation of ammonia to nitrite
Thiobacillus ferrooxidans
- uses iron and sulfur as its electron donors as oxygen as its acceptor.
Geobacter.
uses ferric iron as the electron acceptor.
two major classes off phototrophs
- halophilic archaea
- photosynthetics
halophilic archaea
- use bacteriorhodopsin to harvest light
photosynthetics
- further broken down into two groups depending on whether they use chlorophyll or bacteriochlorophyll
bacteriorhodopsin
- contains the light sensitive pigment retinal.
retinal mechanism of action
- light activated proton pump
- when light strikes the retinal molecule it undergoes a trans to cis isomerization around carbon 13 and loses the proton
- proton passed through series of aspartate residues that form a channel and finally transferred outside of the membrane
- retinal then isomerize back to the trans form
- generates a PMF to create ATP
The light reaction
- creating energy from light, requires light
- uses chlorophyll
- two forms
two forms light reaction
- anoxygenic (bacteriochlorophyll)
- oxygenic (chlorophyll a)
oxygenic photosynthesis
- uses chlorophyll a
- occurs in plants and cyanobacteria or blue green algae
- uses water as e- donor
- generates O2 and ATP
- generates NAD(P)H directly
- involves mostly noncyclic photophosphorylation
- photosystems I and II
Photosystem II
- contains water splitting enzyme that extracts e- from water
- contains manganese, and uses light to remove electrons one at a time from the water
- 4 e- total released
- e- donated to chlorophyll and are energized by a photon, then enter an ETC that pumps protons against PMF to generate ATP
- at end, the e- has lost much of its energy and is delivered to another chlorophyll molecule at the start of PS II
Photosytem I
- begins with e- at ground state
- e- energized to higher energy level then passed to ferredoxin and are used to reduce NADP to NADPH
Bacteriochlorophyll
- water is not reactant
- Thiorhodaceae uses H2S or other inorganic compound
- Chlorobacteriacea uses H2S or other organic compound
- do not produce O2
- cyclic electron flow
Bacteriochlorophyll mechanism
- electrons excited via a photon and travel through ETC of a quinone pool, and b- and c-type cytochromes
- proton gradient set up through Q cycle mechanism
- e- deposited back at same bacteriochlorophyll molecule it started in
- no reducing power made
- electrons must be replaced by external electron donor.
Anoxygenic
- Anaerobic conditions
- Bacteriochlorophyll
- Electron donor of H2, H2S, So, organics
- energy produced: ATP through cyclic photophosphorylation
Oxygenic
- generates O2
- chlorophyll a
- electron donor of H2O
- energy produced: ATP through noncyclic photophosphorylation
- NAD(P)H directly
Carbon fixation
- Calvin-Benson cycle (autotrophs, plants)
- Acetyl-CoA pathway (methanogens and acetogens)
- Reductive Krebs Cycle (Green-sulfur bacteria)
Calvin Benson Cycle formula
- 6 CO2 + 18 ATP + 12 NADPH = Fructose-6-phosphate + 18 ADP + 12 NADP+ + 17 Pi
Calvin Benson cycle
- Dark Reaction
- most carbons fixed by photosynthetics
- ATP and NADPH produced during light reaction used to reduce CO2 into carbohydrate in dark
Rubisco
- carboxylase - most important for calvin cycle
- oxygenase
