Lecture 4 Flashcards
what are the 2 groups that is used to classify metabolism of microorganisms?
- o2 requirement
2. source of energy, electrons and C
what are the 3 groups of microorganisms based on o2 requirement?
- aerobes: requires o2 for growth
- anaerobes: o2 not needed
- facultative aerobe: o2 not required but enhances growth rate
classes of microorganisms based on energy sources?
- chemoorganotrophs: energy sources are organic chemicals
- chemolithotrophs: energy sources are inorganic chemicals
- phototrophs: light
classes of microorganisms based on C sources?
- heterotroph: C from organic chemicals
2. autotrophs: C from Co2
when does fermentation occur?
when nothing can act as the final electron acceptor
doesn’t use ETC
what are the 2 pathways in anaerobic conditions?
- fermentation
2. anaerobic respiration
what is used as the final electron acceptor in anaerobic resp? how do they compared to o2 in energy yield? (redox tower)
something other than O2
if molecule is higher in redox tower than o2 = can produce less ATP = less efficient
if molecule is lower in redox tower = can produce even more energy than o2
(usually toxic = rarely found)
what are denitrifying bacteria?
- when N is used as final electron acceptor in anaerobic conditions
- nitrate (NO3-) becomes Dinitrogen (N2)
how much H+ is pumped out in nitrate based anaerobic resp vs oxidative?
nitrate based: 6H+
oxidative: 8H+
[?]
sulfate reduction vs nitrate in ATP production?
sulfate is higher than nitrate in redox tower = generates less ATP
2 types ofsulfate and sulfur reduction rxns
- desulfuromonas:
- terminal e- acceptor: sulfur (rotten egg smell)
- e- donors: acetate, ethanol - desulfovibrio:
- terminal e- acceptor: sulfate or sulfite
- e- donor: organic or inorganic compounds
2 groups of phototrophs?
- photoautotrophs:
- uses Co2 as C source
- needs environment with lots of light - photoheterotrophs
- uses organic compounds as C source
- lives in environment with less light
light energy = used to generate a pmf
what is oxygenic and anoxygenic photosynthesis?
oxygenic: electrons are taken from H2O (H2o is oxidized to O2)
anoxygenic: doesn’t produce o2. source of electrons are sulfides = produces sulfate)
role of LH1 and LH2?
funnels light energy to the reaction center where the reaction occurs
what pigments participate in the photosynthesis reaction?
only the pigments in the reaction center
ie P680, P700, P840
primary role of carotenoids?
what happens when there is too much bright light?
protect system against bright light
too much light = too much energy = produces toxic forms of o2 = harmful to organism
function of phycobilins?
forms complexes with proteins that are main light harvesting systems = gives another peak of absorbance to the complex
found in microorganisms with very little light environment = allows more production of ATP
site of photosynthesis in plants and algae?
chlorophyll in the chloroplast
describe the pmf across the thylakoid membrane
H+ pumped to interthylakoid space
inside becomes positive and acidic
stroma becomes alkaline and negative
photosynthesis site in bacteria?
pigments are inetegrated in internal membranes
either cytoplasmic, intracytoplasmic, thylakoid membranes or chlorosome
what is the best photosystem to capture light at low intensity??
chlorosome (in green sulfur and green nonsulfur bacteria in deep aquatic habitats)
has antennae systems that transfer light to the RC
describe photosynthesis in purple bacteria
anoxygenic photosynthesis:
needs electron source to reduce NAD+, but P870* does not have enough energy to produce NADH
NADH is produced by reverse electron flow
- energy is supplied by pmf
- electrons are transferred to NADH dehydrogenase (complex 1)
what is the goal of reverse electron flow
to reduce NAD+ to NADH by using energy from pmf when there is not enough light energy
less efficient in producing ATP
describe cyclic photophosphorylation
light is funnelled to the RC > RC is good electron acceptor when in resting state > RC is energized when it receives light > electrons are pushed down the redox tower which allows energy to be harvested > electron goes back to first state > RC is ready to accept another electron
