Bacterial Aerobic Respiration L13 Flashcards
what is the terminal electron acceptor
in aerobic respiration oxygen is used as terminal electron acceptor in electron transport chain
what are the pathways in aerobic respiration
glycolysis
Krebs cycle/citric acid cycle (CAC)/tricarboxylic acid cycle(TCA)
oxidative phosphorylation via electron transport chain
what is the net result of aerobic respiration
all C atoms in glucose are converted to carbon dioxide
38 ATP molecules from one molecule of glucose
where does glycolysis and TCA cycle occur in bacteria
in bacteria glycolysis and the TCA cycle occur in the cytoplasm
what happens to the electrons after glycolysis and TCA cycle
electrons are picked up from intermediates of glycolysis and TCA cycle by NAD /FAD
what produces NADH
conversion of pyruvic acid to acetyl CoA
what does NADH and FADH2 do
NADH or FADH2 take the electrons to the electron transport chain
what creates the most ATP
Most ATP is generated by the chemi-osmotic potential generated as part of electron transport = oxidative phosphorylation
what reactions in glycolysis use ATP
glucose in cell and prepared we start to consume ATP – preparatory reactions use ATP
what happens in stage 2 glycolysis
+2 ATP
+1 NADH
-1 Pi
what is the structure of glucose at the start of the reaction
glucose –> glucose-6-phosphate
what is formed at the end of glycolysis
pyruvate 3 carbon atoms
what is produced in the TCA cycle
3 carbon dioxide
4 NADH
FADH
GTP
what happens in the TCA cycle
pyruvate enters lose COA = acetyl Coa
Lose c if lose a CO2
Join cycle with a4 c
Lose two more carbon round cycle
how does the electron transport system allow energy conservation
production of the proton motive force which is used to synthesise ATP
what is oxidative phosphorylation
electrons ——————->O2
ADP–>ATP
electron flow - proton motive force
what is a classic experiment to show bacteria can grow under a range of different atmospheric conditions
Bacteria are inoculated at low cell density (not visible) into soft agar
Poured into test tubes and incubated to allow growth
agar becomes opaque = growth
Cells evenly distributed in the tube wont move around as embedded in agar
what happens if oxygen is the terminal electron acceptor - patterns of growth in test tube
growth at top where oxygen is
what happens if bacteria grows all through the tube
doesn’t require oxygen for growth
what do patterns reveal - growth of bacteria in test tubes
ability of bacteria to adapt to different levels of oxygen present in their environment
how does the bacterial electron transport chain differ to mitochondria
Bacterial electron transport chains are usually shorter than those in mitochondria
how do the bacterial electron transport chains vary
contain different cytochromes
also contain branches allowing alternative routes of electron flow
what are the cytochromes
CytO
CytD
what is CytO
better at pumping out hydrogen levels, but limited as not as good at finding oxygen
high aeration, fast growth
what is CytD
better at scavenging oxygen when low
low aeration, stationary phase growth
what is NADH
electron donor
what is ubiquinone
(Q) connects NADH dehydrogenase to branches I and II
what happens in electron transport
Electrons pumped out – energise, membrane
Electron go from cytochrome B to O
On other side B B D
Different options of which cytochromes will form complexes
Change depending on the conditions
why does the system change between CtyO and CytD
System I (Cyt D) is better at scavenging oxygen when concentrations are low but is less efficient at pumping out H+ ions System II (Cyt O) is better at pumping out H+ ions but requires higher oxygen concentrations to function Different systems used to optimise energy production depending on the external environment
what is ArcB
transcription regulator
what does the transcription regulator do
senses the levels of O2 and switches from low affinity to high affinity cytochromes
will pickup phosphate and autophosphorylate in response to lower [O2 ]
Transfers phosphate to cytoplasmic ArcA which can regulate gene expression
cytochrome O
cyoABCDE
cytochrome D
cydAB
where is ArcB
in the membrane
what happens in regulation of gene expression by redox-sensitive Arc
- High [O2] ArcB predominates – cyo O made from cyoABCDE
- [O2] drops, ArcB-P formed;
- ArcA-P down regulates cyoABCDE
- ArcA-P induces cydAB
what is the response of further growth patterns
responses are bacteria making different cytochromes
what is a way we can classify bacteria according to growth pattern
bacteria can grow under different atmospheric conditions
what is a strict aerobe
cant grow without oxygen
growth at top of test tube only
example of a strict aerobe
pseudomonas spp.
what is a facultative anaerobe
grows fastest with oxygen but can grow without
growth most at top of test tube and spreads down
what is an example of a facultative anaerobe
Enterobacteriaceae (e.g. Escherichia coli);
has to live in the environment and in the GI tract
what is a microaerophile
requires lower oxygen than atmospheric growth
growth only under the ‘agar’ at top of the test tube
example of a microaerophile
campylobacter
Intestinal pathogen capable of surviving in the environment
what is aerotolerant anaerobe
grows best anaerobically but tolerates oxygen evolved before oxygen around
growth throughout test tube
examples of aerotolerant anaerobe
Lactobacillus & Streptococcus
used in fermentations (cheese & yoghurt)
what is a strict anaerobe
requires O2 to be absent
growth only at the bottom of the test tube
examples of strict anaerobe
Clostridium spp. in soil
C. tetani in deep wounds
C. perfringens causing GI infections
Methanogens in GI tract
what is a canophile
grows best with raised carbon dioxide levels
microaerophiles and aerotolerant anaerobes
