Metabolism Flashcards
What is the metabolic options for obtaining energy
chemotrophy It is receiving energy for organic or inorganic chemicals Chemoorganotrophs (glucose + O2 -> CO2 + H2O + ATP) Chemolithotrophs (H2 + O2 -> H2O + ATP) Or phototrophy phototrophs (light-> ATP)
Whats the carbon flow and energetics for Chemoorganotrophic organic molecules
- carbon flow of CO2 - Biosynthesis - +O2 for Aerobic respiration - Anaerobic respiration (NO3-, SO4^2- as the electron flow) S for proton motive force to yield ATp and organic e- acceptors used.
Anaerobic respiration
Similar or even same Electron Transport Chain as for aerobic respiration Need alternative electron acceptor include inorganic nitrogen and sulphur, carbon dioxide, and iron compounds
Aerobic ETC in Ecoli
input are 2e- from NADH and FADH2 , O2 and 4H+ Outputs are ATP and H2O uses Complex 1, Complex II (Succinate dehydrogenase) complex III and complex IV (cytochrome C oxidase)
Anaerobic ETC in Ecoli
input are 2e- from NADH and FADH2, NO3- and 2H+ Outputs are ATP NO2- and H2O uses complex 1, complex II (fumarate reductase), menaquinone, complex III and complex IV nitrate reductase
Glycolysis
Two reaction series are linked to energy conservation in chemoorganotrophs - fermentation and respiration Differ in mechanism of ATP synthesis - Fermentation: substrate-level phosphorylation; ATP directly synthesized from an energy-rich intermediate - Respiration: oxidative phosphorylation; ATP produced from proton motive force formed by transport of electrons
Chemo-organotrophy
Metabolism of glucose under aerobic conditions. Stage I Preparatory reactions. Stage II Making of pyruvate and synthesis of ATP by substrate level phosphorylation Stage III The fate of pyruvate
Variations in fermentation end products
The citirc acid cycle
•Citric acid cycle: pathway through which pyruvate is completely oxidized to CO2
–Initial steps (glucose to pyruvate) same as glycolysis
–Per glucose molecule, 6 CO2 molecules released and NADH and FADH generated
–Plays a key role in catabolism and biosynthesis
•Energetics advantage to aerobic respiration
How much ATP is made per glucose in aerobic respiration
what is the carbon flow and energetics of chemolithotophic metabolisms
CO2 -> biosynthesis
NO3- and SO42- are used for electron flow
O2 is given off
S0 used in proton motive force to yeild ATP
Chemolithotrophy - electron flow during Fe 2+ oxidation by the acidophile Acidithiobacillus ferrooxidans
Ferrous iron oxidation begins in the outer membrane where a cytochrome C proteins oxidizes Fe2+ to Fe3+
Electron transferred to periplasmic protein Rusticyanin which then reduces cytochrome c, and this subsequently reduces cytochrome a
Cytochrome a interacts with O2 to form H2O
ATP is synthesized by ATP synthase in the membrane
Autotrophy in Acidothiobacillus ferrooxidans is driven by the Calvin cycle
Energetics and carbon flow on Phototrophic metabolism
- Photo heterotrophy
biosynthesis made from organic compounds
Photoautotrophy
biosynthesis made from CO2
Light->Electron flow->Proton motive force -> ATP
Two types of Phototrophs
Anoygen (purple and green bacteria)
reducing power comes from H2S -> S0 -> SO42-
Oxygenic (cyanobacteria, algae, green plants)
reducing power from H2O-> 1/2O2
both use light to make ATP from ADP
Bacterial photosynthetic membranes
Chlorophylls and associated components of light gathering machinery are located in various membrane structures
Allows production of energised membrane
Varied arrangements
Cell membrane (CM) derived vesicles (purple bacteria)
CM itself (Heliobacteria)
Both CM and physically associated chlorosomes (Green bacteria)
Thylakoid type membranes similar to chloroplasts (cyanobacteria)
whats the electron flow in anoxygenic photosynthesis in purple bacteria
steps in photosynthetic electron flow are much the same as that of respiratory electron flow
For a purple bacterium to grow autotrophically, the formation of ATP is not enough
Reducing power (NADH) is also necessary
Reduced substances such as H2S are oxidized and the electrons eventually end up in the “quinone pool” of the photosynthetic membrane
Whats the arrangement of Protein complexes in the photosynthetic membrane of purple photosynthetic bacterium
the calvin cycle
The Calvin cycle
Named for its discoverer Melvin Calvin
Fixes CO2 into cellular material for autotrophic growth
Requires
NADPH, ATP, ribulose bisphophate carboxylase (RubisCO), and phosphoribulokinase
6 CO2 to 1 molecule of glucose
Green sulfur bacteria use the reverse citric acid cycle to fix CO2
Green non-sulfur bacteria use the hydroxypropionate pathway to fix CO2
