Lecture 13 Metabolism III Flashcards
What are the two types of photosynthesis
Anoxygenic and oxygenic
Anoxygenic harvested energy from light in ocean
Oxygenic evolved from anoxygenic
What is the significance of methanogenisis
Mineralization of organic matter on the subsurface
Major role in digestion process of ruminant animals
Produces biogenic methane gas from coal and oil
Anaerobic digestion to produce biogas from compost, Waste water treatment
How does oxygenic photosynthesis work?
Excites chlorophyll, excites rxn centre’s with PSI AND PSII, decreasing reduction potentials
Cyclic photophosphorylation
Involves PSI and produces ATP
Non-cyclic
Involves production of reducing energy and NADPH
Electrons are donated by H2O to PSII. NADPH is used for co2 fixation
How does anoxygenic photosynthesis work?
Purple non sulfur bacteria
Electron donors: H2S
Don’t have enough reducing potential too low
Reducing power must be generated by PMF
Green non sulfur bacteria
Can directly DIVERT ELECTRONS FROM FAD to NAD
What is reverse electron transport
It’s a a method that’s used by anoxygenic phototrophs and chemolithotrophs to generate reducing power to produce NADPH or fadh2.
Proton gradient provides energy for reverse electron transport
What is methanogenisis?
Produce methane, anaerobic process
Oxidation of h2 coupled with reduction of CO2
Key enzyme: mcr
What is hydrogen oxidation?
Oxidation of H2
H2 is an excellent donor, TEA O2, enzyme is hydrogenase, can transfer electrons directly to NADP
What is the key enzyme of ammonia oxidation?
AMO (ammonia monooxygenase)
What is the specialized organelle in Annamox?
Annamoxosome
Protects the cell from reactive intermediates, where metabolism takes place
What is Anammox?
Anaerobic ammonia oxidation
Oxidation of ammonia coupled nitrite reduction to produce N2
Beneficial process to waste water treatment! Does not require o2
Under what conditions can FE oxidation occur?
Acidic and neutral
Oxygen is the TEA for acidic or nitrate for neutral
What is the electron donor in anammox?
Hydrazine , it’s every electronegative and donates electrons to Fe
Intermediate of metabolism
It’s also used in rocket fuel
Very oxygen sensitive
What are the two different functional types of nitrification ?
Ammonia oxidizing bacteria (AOB)
Nitrogen oxidizing bacteria (NOB)
Which pathway is used by many strict anaerobes including methanogenisis?
Reductive acetyl coA pathway
Which enzymes catalysts the addition of CO2 to RuBP in the Calvin cycle?
Rubisco
What are the phases of the Calvin cycle?
Carboxylation, reduction, regeneration
What is synotrophy?
Metabolic process in which two organisms cooperate to degrade a substance and conserve energy
What is the purpose of the carboxyxomes in the Calvin cycle?
They serve to concentrate co2 in many microbes
What is diazotrophy
Specific type of autotrophy, involves nitrogen fixation to make nitrogen readily available, nitrogen gas to ammonia
Free living cyanobacteria
Nitrogrenase is a key enzyme
-Oxygen sensitive
How do aerobic nitrogen fixers manage?
They physically separate from oxygen rich environments, form cells
Autotrophy C fixation
Assimilation of CO2 into cell material
Overall objective is to convert CO2 to glucose
Pathways: Calvin cycle, reverse TCA, reductive acetyl coA
What happens in carboxylation
Rubisco catalyze the addition of CO2 to RuBP forming 2 PGA
Reduction in Calvin cycle
PGA reduced to bisphosphoglycerate
Regeneration in Calvin cycle
Regeneration of RuBP
Reductive reverse tca cycle
Operates in certain anaerobic bacteria and archaea
Used by many chemolithotrophs
Purpose: carbon fixation in the absence of oxygen
Nadph production
Reductive acteyl coa, energy requirements
In methanogens: no atp required, pmf is used to reduce fd and co2
In bacteria: nadph is used to reduce co2 1 atp is required to generate formyltetrahydrofolate
Interspecies H2 transfer
A process where H2 is transferred from the syntroph to the methanogeni
What does nitrification do?
Two step, oxidation of ammonia (nh4+) to nitrite (no2-) and then to nitrate (no3-)
What do anomoxosomes do?
Protect cells from reactive intermediates like hydrazine (rocket fuel)
Protons accumulate within this organelle —> producing PMF
ATP synthase located on the membrane
Compare Assimilatory (anabolism) vs Dissimilatory (catabolism) reduction
Assimilation
-INPUT OF ENERGY
- reduction of inorganic sources of elements into organic forms for BIOSYNTHESIS
-only enough reduction to satisfy the needs of biosynthesis
Dissimilation
- generation of ENERGY
-reduction of inorganic forms for energy production
- electron accepor gets reduced and excreted (metals, NO3, CO2)
- large amount of electron acceptor used
(Synotrophy) Many fermentations are not thermodynamically feasible… solution?
shift equilibrium, remove the products! low concentration
how? couple it with a favourable one
who? 4H2 + CO2 –> CH4 + 2H2O
-130 kj/mol
makes it exergonic example
removal of the H2 product pulls ethanol fermentation to the right overall exergonic.
Purpose of Anaerobic food webs
drive carbon cycling in both natural and anoxic environments.
hydrolysis –> fermentation –> terminal respiration
methane is the main product of degradation (biogas ferment waste)
