Unit 2--Lecture 8 (Fermentation and Respiration) Flashcards
Regenerating NAD+
Glycolysis = 2 NADH
Entner-Doudoroff = 1 NADH & 1 NADPH
TCA = 4 NADH & 1 FADH2
Pentose Phosphate also regenerates reduced NAD(P)H molecules
Two main ways to regenerate NAD+
Organic: fermentation
Inorganic: Respiration
Fermentation
Organic
Performed by anaerobic microorganisms
Primary purpose: regenerate NAD
Secondary purpose: generate additional energy
Mixed Acid Fermentation
E. coli
Metabolic flexibility
Dumping electrons vs ATP generation
Produces acetate and ethanol
Some bacteria can do TCA backwards (gets rid of electron)
Redox Potential Energy
Best donors (least electronegative) at top
Best acceptors (most electronegative F/O) at bottom
Electron Transport Systems
Occurs on membranes
Inner membrane of bacteria/archaea (cytoplasmic membrane)
Inner membrane of mitochondria/chloroplasts
The Respiratory ETS
Electrons from NADH –> O2 release energy
—-requires intermediates
—-multiple steps
NADH Oxidase
Quinones
Cytochromes
Flavoproteins
Cofactor
FAD or FMN
Carry 2 protons, 2 electrons
Quinones
Isoprenoid lipids
UQ, MQ, PQ
Carry protons and electrons
Iron Sulfur Proteins
Electron carrier only
Cytochromes
Iron + heme
Electron carriers only
Mitochondrial Respiratory ETS
4 Complexes
I: e- from NADH to Coenzyme Q
II: e- from FADH2 to Coenzyme Q
III: Coenzyme Q to Cytochrome C
IV: Cytochrome C to O2 (aa3)
Driving protons out of cytoplasm
NADH = 10 H+ out
FADH2 = 6 H+ out
E. coli Respiratory ETS
NDH-1 pumps 4 protons and 2 electrons
NDH-2 pumps 0
Cytochrome bo pumps 1 proton and 1 electron
Cytochrome bd pumps 0
NDH-1 —> Q —> Cytochrome bo
Proton Motive Force (PMF)
PMF used directly for cell activities:
Creates ATP
—-ATP synthase at cell membrane
Drives flagellar rotation
—-motors at base of flagella
Pushes ions into, out of cell
—-Symport: same direction as proton movement
—-Antiport: opposite direction
Proton Potential Creates ATP
F1 F0 ATP synthase makes ATP
Protons enter the F0 subunit and cause it to rotate
F0 rotation drives the
F1 subunit shaft
Synthesizes ATP from ADP + Pi
KNOW FOR EXAM
ATPase: 3 H+ in = 1 ATP
NADH: 10 H+ out = 3 ATP
FADH2: 6 H+ out = 2 ATP
Glycolysis & Fermentation:
1 glucose
—> 2 lactose
2 ATP
Glycolysis & PDH & TCA
glucose
—> 2 pyruvate
2 NADH
2 ATP
—> A-CoA
2 CO2
2 NADH
—> 4 CO2
6 NADH
2 FADH2
2 ATP
Totals:
4 ATP
10 NADH = 30 ATP
2 FADH2 = 4 ATP
6 CO2
————————–
38 ATP (max)
Anaerobic Respiration
Environment lacks oxygen
Use other terminal electron acceptors
—-nitrogen compounds
—-sulfur compounds
—-metals (manganese, iron)
Lithotrophy
Many materials donate electrons if a better acceptor is present
Nitrogen
Sulfur
Iron (or even hydrogen)
Methanogensis
Hydrogen donates electron
CO2 can accept electrons
High CO2 concentrations drive reaction
Important anaerobic reaction
Phototrophy
Bacteriorhodopsin absorbs light
Excites electrons
Return to ground state
Releases energy
Generates proton gradient
Chlorophyll absorbs light
Different chlorophylls absorb wavelengths
Determines where an organism can grow
—-purple bacteria
—-green bacteria
—-cyanobacteria
—-plant chloroplasts
Purple Bacteria/Reactions
Reactions:
—-ADP + Pi –> ATP in presence of light
—-Able to make tons of ATP
—-Still need to generate NADH
—-Bacteriochlorophyll is not a good enough donor, must use reverse electron transport
Light Harvesting:
—-Found in cell membrane
—-Bacteriochlorophyll-protein-carotenoid complex
—-Antennae complex closely associated with the reaction center
—-Cell membrane highly invaginated to increase surface area
Green Sulfur ET, Reactions, Light Harvesting
Electron Transport:
—-reduce Fe/S centers
—-instead of quinones
Reactions:
—-no reverse electron transport
—-use inorganic sulfur
—-generate ATP and NADH
—-H2S + NAD + ADP + Pi –> S + NADH + H + ATP
Light Harvesting:
—-bacteriochlorophyll c, d, or e
—-protein and carotenoid
—-localized in chromosomes
Oxygenic Photosynthesis
Plant-like photosynthetic apparatus
Alternatively, plants are bacteria-like
Performed by the cyanobacteria (formerly blue green algae)
Extremely important to life on earth
Cyanobacteria and Algae
Found in the chloroplast or bacterial membrane
Two photosystems
Purple + Green
Non-cyclic electron flow
Water is oxidized to O2
