PMB 112 Final Review
How to measure antimicrobial activity? - ANS-Make a very dilute suspension of the
pathogen in growth medium and aliquot equal volumes into a series of culture tubes.
Add increasing concentrations of the antibiotic to the tubes, from ~1 μg/ml to ~1 mg/ml.
Allow all cultures to grow overnight. The tube with the lowest concentration of antibiotic
in which there was NO GROWTH of the bacteria represents the MIC.
MIC: minimal inhibitory concentration
lowest concentration of an agent that completely inhibits growth
What is biosignature? - ANS-Characteristics:
Specific organic molecules found in sedimentary rock
Dated by the age of the rock formations in which they are found
Molecules are known to be formed only by microbes
--
EX: hopanoids: cholesterol structure on the membrane of bacteria that can be highly
specific
What are metabolites options for obtaining energy? - ANS-
What are two types of phototrophy based on different light utilizing molecule? -
ANS-Rhodopsin:
Containing retinal
only photoheterotrophs
No photoautotrophs
Creating proton motor force
--
Photosynthetic reaction centers (RCs) with chlorophyll
All photoautotrophs and some photoheterotrophs
Creating proton motor force
What is the photoautotroph reactions - ANS-Light reaction:
,light energy to chemical energy and reducing power
Dark reaction:
chemical energy and reducing power reduce Co2 to organic compounds (CO2 fixation)
What is the reaction of photosynthesis? - ANS-CO2 electron acceptor
Electron donor:
oxygenic photosynthesis - water
anoxygenic photosynthesis - H2S and other reduced chemical
Which bacterias perform anoxygenic photosynthesis? - ANS-Purple bacteria, green
sulfur bacteria, heliobacteria
Anoxygenic VS. Oxygenic photosynthesis - ANS-Defined by whether or not the process
produce oxygen
Light energy is used for proton gradient for ATP synthase
What are difference between chlorphyll a and bacteriochlorophyll a - ANS-All
photoautotrophs use RC with chlorophyll
Both porphyrins, similar to heme
c pigments associated with photosynthetic membranes usinig phytol group (similar to
bactoprenol)
Two types of photosynthetic reaction center - ANS-Type 1 : photosystem 1 (Q type)
Fe/S cluster as electron acceptor
Type 2 photosystem 2 (Fe-S type)
Quinone as acceptor
Function:
Both generating PMF and reducing power
What are the principles of photosynthetic Electron transport - ANS-1. Light energy
excite special chlorophyll in the reaction center
2. Electron flow downhill with more positive E0
,3. Electron transport is coupled to proton translocation -> generate PMF
4. First electron acceptor with E0 greater than NAD+. reverse electron flow occur at the
expense of generating NADH
What is the electron flow in anoxygenic photosynthesis looks like? - ANS-P870 absorb
lights and convert to excited states P870*
Better electron donor and thus donates an electron to next acceptor
Proton is pumped out by Q pool to create PMF
When electron are drawn off an electron from another source need to re-reduce p870
How does anoxygenic photosynthesis generate PMF and reducing power? - ANS-Cyclic
electron flow -> PMF
Reverse electron flow -> reducing power
how does cyclic eletron transport generating PMF? - ANS-The light generated proton
gradient is used for ATP synthase
Comparison of electron transport in anoxygenic phototrophs - ANS-Purple bacteria:
reverse electron flow generate NADH
Green sulfur and heliobacteria:
Fe/S cluster is the first stable electron accetor that could directly reduce to Fd (E donor
for CO2 fixation)
or could re-reduced by other electron donor like H2 or H2S
What does oxygenic photosynthesis use? - ANS-Combination of Q type and Fe/S type
RC
What is the process of Z scheme oxygenic photosynthesis - ANS-PHOTO I
------
Light energy excites P680 -> p680*
Expel an electron and reduce ph
, Reduce mobile PQ pool to Cyt bf --> releasing proton to periplasm creating PMF
Proton pumped again when Cyt bf pass electron to PC, proton is in P700
PHOTO2
-------
P700 to P700*
Reduce FeS protein to Fd
What are the two ways electron on Fd could go on? - ANS-1) Travel to Fp and reduce
NAD+ to NADH
- noncyclic photophosphorylation
- both PMF and reducing power
2) Electorn on Fd return to cyt bf and travel back trough PS1 using more light energy
- cyclic photophosphoylation
- only PMF no reducing power
How does P680 and P700 back to ground state? - ANS-p700 - electron from
plastocyanin
p680 - electron from splitting of water (happening in oxygen evolving complex)
Where is the photosynthetic apparatus located? - ANS-Specialized membrane system
1) Thalakoid membrane for cyanobacteria
2) Chlorosomes for green sulfur bacteria
What are three classes of light harvesting pigments/ - ANS-Chlorophylls
- synthesized by tetrapyrrole pathway
Phycobilins
- synthesized by tetrapyrrole pathway
Carotenoids
What is the absorption spectra of chlorophyll and why? - ANS-energetic niches
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