Lecture 9: Metabolism Flashcards
Most organisms we will study are in what group?
chemoheterotrophs
chemoheterotrophs
Organisms that use organic carbon compounds
as sources of both carbon and energy
What category do all pathogens and many well categorized bacteria fall into?
chemoheterotrophs
saprophyte
an organism that uses dead
organic material for nutrients
parasite
an organism that feeds of living organic matter
Metabolic pathways for energy storage
- glycolysis (Embden Meyerhoff Pathway)
- photosynthesis
- cellular respiration
alternatives to glycolysis in bacteria
- pentose phosphate pathway
- Entner Doudroff pathway
photosynthesis
conversion of incident light into ATP
- two pathways: cyclic and non-cyclic
Cellular respiration
- aerobic respiration (Krebs cycle)
- anaerobic respiration: uses a different terminal electron acceptor (sulfate or nitrate)
Non-photosynthetic metabolism (aerobic and anaerobic)
Respiration is the
aerobic process
Fermentation is the
anaerobic process
Glycolysis pathway to pyruvate differences between respiration and fermentation
it is the same in both
What are all metabolic pathways regulated by?
enzymes
How many stages in glycolysis?
2
- preparatory stage
- conversion to pyruvate
Preparatory stage of glycolysis
The preparatory
stage is enzymatic
processing of
glucose
The addition of
phosphate groups
costs the cell energy
in the form of ATP
Glycolysis - conversion to pyruvate: step occurrence, net gain, and what the products do
- in this
set of steps, all
reactions occur
twice
Net gain from
glycolysis is 2
molecules of ATP
and 2 molecules
of NADH which
can donate electrons in the electron transport chain
Pentose phosphate pathway anaerobic or aerobic?
either
What is pentose phosphate pathway important for?
important in biosynthesis as well
what can pentose phosphate pathway operate in tandem with?
glycolytic
What do the early steps of pentose phosphate pathway produce?
NADPH + H+ (energy)
What do the later steps of pentose phosphate pathway do?
Later steps shunt to
biosynthesis or TCA
cycle
Entner-Doudoroff
- Similar role to
Embden-Meyerhof
glycolysis
Instead of using 2
ATP, uses 1 ATP in 6
carbon stages
Key intermediate
KDPG 2-keto-3-deoxy-
6-phosphogluconate
Found mainly in some
G- as substitute for
glycolysis
Why do we care about Entner-Doudoroff pathway
the key intermediate allows us to tell specific bacteria apart, just by their use of KDPG (because a lot of bacteria all look the same)
Fermentation
- anaerobic
- pyruvate degraded to form organic end products (like ethanol)
- general mechanism is widespread in bacteria
- makes food, chemicals, and medicine
What does chemiosmosis use and what for?
Use electrons to generate proton gradient
What does chemiosmosis allow for?
Allow protons to flow across membrane, use
ATPase running backwards to generate ATP
Where does chemiosmosis happen?
- cellular membrane in bacteria
- inner membrane of mitochondria (alpha proteobacteria)
What is the point of proton motive force?
Goal of this system is
to create a proton
gradient
What is going on in proton motive force?
(protons are pumped across the membrane coupled to oxidation of carriers (NADH, NADPH, FADH2)
- protons flow through F1F0 ATPase
- 2 or 3 H+ yields 1 ATP
Best electron acceptors
- oxygen (the best e- acceptor)
-> allows many starting materials
What alternative e- acceptor is useful in anaerobic niche?
TEA
-> but not as high energy
Electron transport in different bacteria
E. coli:
Use NADH, FADH2
Uses at least 5 cytochromes
Oxygen as terminal electron acceptor
Uses different cytochromes depending on PO2
Fairly inefficient, gets ~1.3 ATP per Oxygen
molecule (P/O) ratio
Paracoccus denitrificans:
- Can grow
heterotrophically
or autotrophically
Autotrophy- uses
H2, CO2, NO2
NO2 is terminal
electron acceptor
anaerobically
Reduced to N2
How to study ETC
- P/O ratio describes efficiency of aerobic respiration (ATP produced per O2)
- proton motive force can be studied using uncouplers (ionophore)
- molecules that interfere with gradient or inhibit..)
