L8 bacterial aerobic cellular respiration Flashcards
breakdown of proteins before entering the TCA cycle
protein -> amino acid (using protease)
deamination: NH2 is removed
amino acid is primarily transaminated.
amino group is removed and turned into glutamate
glutamate-> alpha-ketoglutarate (carbon skeleton)
Aketo gets fed into TCA cycle (central pathways)
breakdown of sugars for the TCA cycle
starch-> glucose
glucose gets metabolised by glycolysis -> pyruvate
pyruvate goes into TCA cycle
breakdown of lipids to fatty acids
2 ways
lipid-> fatty acid-> Acetyl CoA -> CoA enter TCA cycle
lipid-> glycerol -> glycolysis
what do the specilised pathways of molecule breakdown do
isolate the conserved carbon backbone so it can go through glycolysis or the TCA cycle
what are the two phases of glycolysis
energy investment phase
energy payoff phase
what happens during the energy investment phase
2 ATP is used to doubly phosphorylate glucose
6C molecule is cleaved into two 3C chains
what happens during the energy pay off phase
the 2, 3C molecules are converted into pyruvate
how many steps and what happens in them during the energy pay off stage
2 steps
4 ADP + 4P -> 4ATP
2NAD+ +4 e + 4H+ -> 2 NADH + 2H+
what is the net yield of pyruvate
2ATP 2 pyruvate 2 H2O 2NADH (6 precursor metabolites)
what would happen to the pyruvate if E.coli was in a anaerobic environment
pyruvate would undergo lactic acid fermentation to produce ATP
what happens to the pyruvate under aerobic conditions
undergoes complete combustion to CO2
through TCA acid
what happens to pyruvate during TCA cycle
converted into acetyl CoA which produces CO2 and NADH
how many precursor metabolites are produced during TCA cycle
4
what does the TCA cycle produce lots of
NADH
what is FADH
electron carrier of slightly lower potential than NADH
what 4 precursor metabolites are produced
acetyl CoA
alpha-ketoglutarate
succinyl-CoA
oxaloacetate
what is used to convert pyruvate to acetyl CoA and what is produced
pyruvate dehydrogenase
1 NADH
why does the TCA cycle only occur in aerobic bacteria
Because the NADH needs to be converted back using an electron transport train in order to keep functioning
what are the products of 1 full cycle of TCA
3 NADH
1 GTP
1 FADH2
what is the yeild from 1 glucose molecule through glycolysis and TCA cycle
10 NADH, 2 FADH2, 2 ATP, 2 GTP
what are the two ways bacteria like E.coli can make ATP
substrate-level phosphorylation (SLP)
oxidative phosphorylation
what is substrate level phosphorylation
makes ATP as a consequence of cytoplasmic reactions (no membrane bound proteins)
-uses cytoplasmic enzymes (pyruvate kinase)
example of substrate level phophorylation
PEP-> pyruvate +ATP using pyruvate kinase
why is
PEP-> pyruvate +ATP using pyruvate kinase
favourable
the energy of cleaving a P from PEP is more negative than ATP
ATP does not have enough energy to phosphorylate PEP
where is another example of substrate level phosphorylation
during the TCA cycle when GDP is turned into GTP
disadvantage of substrate level phosphorylation
low efficiency
limited without regenerating NAD+ (fermentation)
advantages of substrate level phosphorylation
simpler and not limited by electron acceptor
why is OXPHOS so important
recycles all of the NADH and FADH2 from the central pathways
what enzyme is involoved in YCA cycle and electorn transport chain
succinate
what system is used in OXPHOS
electron transport chain
how much more efficient is OXPHOS than SLP
10x more ATP is produced
what are the four major components of the electron transport chain of mitochondria
complex I Complex II: succinate dehydrogenase complex III: cytochrome bc 1 complex IV: cytochrome c oxidase ATP synthase
what is the gst of the electrorn transport chain
oxidises NADH and transport electrons through to pump protons across the membrane
what is the electron transport chain limited by?
availability of an electron acceptor
where do the electrons from the transport chain go?
put onto oxygen hence why it is needed
order the type of respiration from most to least efficient and yield per glucose molecule
aerobic: 38
microaerobic: 15
Anaerobic nitrate: 15
anaerobic fumarate: 12
fermentation Acetyl CoA: 3
why is oxygen the best electron acceptor ?
it has the lowest redox potential/ most far from NAD
features of electron transport chains
a membrane
membrane-bound oxidative protein complexes
Co-factors
membrane-bound reductive protein complexes
role of a membrane in ETC
physical barrier to create conc gradient
role membrane-bound oxidative protein complexes in ETC
liberate electrons from reducing power and MAY pump H+
role of co-factors in ETC
transfer electrons between enzymes
role of membrane bound reductive protein complexes in ETC
finally transfer electrons to terminal electron acceptor MAY pump H+
example of a membrane
cytoplasmic membrane
example of oxidative complex
complex I
takes NADH-> NAD+
does complex I pump protons?
yes
does complex II pump protons
no
what are co factors
transfers electrons between enzymes by being reduced and oxidised
example of a co factor
quinones (ubiquinone + menaquinone)
what are quinones
conjugates between the electron-donating and electron-accepting reaction
example of redcutive protien complex
complex III
complex IV
what do complex II and IV do?
take the ubiquinol (reduced quinone) and oxidise it back to the quinone
which two complexes make up the super complex in TB(mycobacteria) bacteria electron transport chain
III and IV
differences between mitochondrial and bacteria electron transport chain
ndh enzyme
complexx III and IV are a super complex
cyd enzyme
what enzymes in bacteria electron transport chain reduces NADH
complex I
ndh
is ndh a proton pump?
no
what cofactor does bacteria use
menaquinone
which enzymes do the bacteria electron transport chain have that can use oxygen
super complex
cyd
is cyd a proton pump
no
can TB respire without oxygen
no
what happens when TB doesn’t have oxygen
goes into persistance and stops replicating
what happens when you starve E.coli of oxygen
TCA cycle gets shut down
start to reverse the TCA cycle
why does the E.coli TCA cycle operate in reverse under anaerobic conditions
E.coli uses fumerate to produce ATP
what electron acceptors can E.coli use except O2/ use to respire
fumerate nitrite nitrate DSMO TMNO
what does E.coli do when it runs out of electron acceptors
begins fermentation
what is made during fermentation that can be used as an electron donor
formate
what is the key enzyme for aerobic respiration
cytochrome bo
what is the key enzyme for microaerobic respiration
cytochrome bd
what is the key enzyme for anaerobic respiration
nitrate reductase nitrite reducates fumerate reductase DMSO reductase TMAO reductase
what are the key enzymes for fermentation
lactate dehydrogenase
formate hydrogenlyase
