Catabolism on chemoorganotrphs Flashcards
3 ways biology generates ATP
-substrate level phosphrylation
-oxidative phosphorlyation
-photophosphorylations
substrate level phosphrylation
-ATP generated as a product of a metabolic reaction
-exergonic rxn - use excess energy to make ATP
oxidative phosphorylation
-energy from electron transfer generate a proton motor force, which is used to generate ATP
photophosphorylation
-energy captured from light is used to generate proton motive which is used to generate ATP
catabolism of glucose
-for many chemoorganotrophs, sugars like glucose are a preferred energy source. They carry out the net reaction above in a series oxidation reactions
-many other organic compounds can also be used to generate enrgy, often using overlapping pathways
-many other sugars can be used too
glycolysis
-glucose broken down to two pyruvate molecules over several steps
-found in all domains of life
-quick way to produce energy from glucose also feeds into CAC
-does not require O2
-can be followed by either respiration or fermentation
glycolysis photo
glycolysis overall net reaction
citric acid cycle
-step 1- pyruvate converted to acetyl COA, Acetyl COA then enters the CAC
-sugars and other organic molecules can feed into the CAC
-cycle not just for catabolic purposes also provides key metabolic intermediates used anabolic reaction
-not just found in aerobic chemotrophs
-takes place in mitochondria in eukaryotes
citric acid cycle photo
citric acid cycle overall
CAC and redox imbalance
-CAC did not solve our redox imbalance from glycolysis it made it worse
-the electron transport chanin and respiration is how this is solved
electron transport chain
-cytoplasmic membrane (inner mitochondrial membrane for eukaryotes)
-redox baalnce restored and eNAD+ (electron carrier) regenerated
-electrons passed down a series of electron carriers with increasingly positive reduction potentials until a final electron acceptor is reduced
-P+ pumped out of cell to generate proton motive force
-O2 is terminal electron acceptor
electron transfer in ETC
-from lower reduction potential carriers to higher reduction potential carriers and then to a final electron acceptor
-final electron acceptor gets used up, so you need a continous source to keep this going
iron sulfur proteins
-key electron carrier
-metal cofactors used by many different proteins involved in electron transfer
-ETC comlexes often contains multiple Fe/S cluster
-oxidation state and reduction potential varies depending on nature and cluster of protein
quinones
-key electron carrier
-not protein - small molecule that move within membrane
-accept 2 electrons transfer to next carrier in chain
-often serve to link Fe/S proteins to cytochromes
cytochromes
-cytochromes are proteins that contain heme prosthetic groups
-different proteins/different heme groups, different reduction potentials
-ETC compelxes often contain multiple cytochromes-typically the last stop before terminal acceptor
electron transport chain paracoccus dentrificans
complexes
multiple proteins
-can include proton pumps that couple energetically favourable electron transfer to proton pumping
where can electrons enter in the ETC in paracoccus dentrificans example
-this specific can enter at complex I or Complex II
-complex one starts with NADH and pumps 4 p+ per 2e- to generate more energy
-complex II starts with FADH2, pumps fewer protons
-from either complex I or II, quinone is reduces and passes electrons on to complex III
hoe many protons pumped from NADH to H2O in ETC paracoccus example
-10 protons per NADH
ATP synthase
-proton motive force to ATP
-protons flow back along their gradient-generates mechanical energy
-mechanical energy then used to power the phosphorylation of ADP–> ATP
-approx 3.3 H pumped needed to generate 1 ATP
-reversible, ATP hydrolysis ca generate PMF
how many ATP per NADH
3
metabolic flexibility of chemoorganotrophs
-chemoorgannotroph have preferred energy source but can use a variety of other molecules such as fatty acids –> acetyl CoA and AA converted to entry pounts to CAC
-many possible terminal electron acceptors
-some microbes have the ability to use multiple different terminal electron acceptors
Ecoli aerobic and anaerobic respiration
-facultative anaerobe
-can do respiration, anaerobic respiration and fermentation
-can assemble different electron transport chains
-under aerobic conditions conditions can respire using nitrite or DMSO
-nitrate respiration is less efficient as it puumps fewer protons than with O2
fermentation
-chemotrophic metabolism without use of an external electron acceptor
-anaerobic
-substrate level phosphorylation can be used to generate ATP
-Redox balance achieved by excretion of reduced fermentation products
Lactic Acid fermentation
ethanol fermentation
Diversity of fermentation
-microbes can fermenet a wide range of organic compounds (AA, Fatty acids, purines and pyrimdines)
-a range of other fermentation products can be made
-generate energy rich molecule that can be hydrolyzed to produce ATP, donate electrons to reduce a metabolite and excrete it to obtain redox balance
-fermentation can vary from last report option to the sole source of energy
beer
-ethanol generated by yeast alcoholic fermnatation used to make alcoholic beverages
-The CO2 generated by alcoholic fermentation used to make dough rise
-the CO2 can also be used to naturally carbonate beer
