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CHAPTER 6 : BIOSYNTHESIS AND REGULATION - Coggle Diagram
CHAPTER 6 : BIOSYNTHESIS AND REGULATION
RESPIRATION
using reducing power (NADH, FADH2)
generates by glycolysis, transition step & TCA cycle
called chemiosmotic theory
ELECTRON TRANSPORT CHAIN
membrane embedded electron carries
prokaryotes : in cytoplasmic membrane
eukaryotes : in inner mitochondrial membrane
creates electrochemical gradient
prokaryotes can also power transporters, flagella
pass electron sequentially, eject protons in process
energy gradually released
release coupled to ejection of protons
components of an electron transport chain
Quinones : lipid soluble molecules & move freely, can transfer electrons between complexes
Cytochromes : contain heme, molecule with iron atom at center & several types
Flavoproteins : proteins to which a flavin is attached & FAD, other flavins synthesized from riboflavin
general mechanisms of proton ejection
some carriers accept only hydrogen atoms
spatial arranegement in membrane shuttles proton to outside of membrane
when hydrogen carriers accepts electron from electron carrier, it picks up proton from inside cell / mitochondrial matrix
when hydrogen carrier passes electrons to electron carrier, protons released to outside of cell / intermembrane space of mitochondria
net effect is movement of protons across membrane
establishes concentration gradient
driven by energy released during electron transfer
electron transport chain of mitochondria
COMPLEX I (NADH DEHYDROGENASE COMPLEX)
accepts electrons NADH, transfer to ubiquinone
pumps 4 protons
COMPLEX II (SUCCINATE DEHYDROGENASE COMPLEX)
accepts electrons from TCA cycle via FADH2 "downstream" of those carried by NADH
transfer electrons to ubiquinone
COMPLEX III (CYTOCHROME BC1 COMPLEX)
accepts electrons from ubiquinone from COMPLEX I / COMPLEX II
4 protons pumped, electrons transferred to cytochrome c
COMPLEX IV ( CYTOCHROME C OXIDASE COMPLEX)
accepts electrons from cytochrome c, pumps 2 protons
terminal oxidoreductase, meaning transfer electrons to terminal electron acceptor (O2)
electron tranpsort chain of prokaryotes
TERMENDOUS VARIATION : even single species can have several alternate carriers
E. coli serves as example of versatility of prokaryotes
AEROBIC RESPIRATION IN E COLI
succinate dehydrogenous equivalent to complex II of mitochondria
can produce several alternatives to optimally use different energy sources, including H2
lack equivalents of complex III or cytochrome c
can use 2 different NADH dehydrogenous
ANAEROBIC RESPIRATION IN E COLI
harvests less energy than aerobic resporation
some components different
can synthesize terminal oxidoreductase that uses nitrate as terminal electron acceptor
sulfate - reducers use sulfate as terminal electron acceptor
CHEMOLITHROTROPHS
prokaryotes unique in ability to use reduced inorganic compounds a source of energy
CARBON FIXATION
in photosynthetic organisms : light independent reactions
consumes lots of ATP , reducing power
calvin cycle most commonly used
three essential stages
incorporation of CO2 into organic compounds
reduction of resulting molecule
regeneration of starting compound
six " turns" of cycle : net gain of one fructose-6-phosphate
FERMENTATION
fermentation used when respiration not an option
E. coli facultative anaerobe
aerrobic respiration, anaerobic respiration and fermentation
Streptococcus pneumoniae
fermentation only option
ATP - generating reactions are only those of glycolysis
additional steps consume excess reducing power : regenerate NAD+
fermentation end products varied, helpful in identification, commercially useful
ehanol
butyric acid
propionic acid
2,3 - Butanediol
mixed acids
PHOTOSYNTHESIS
plants, algae, several groups of bacteria
can be considered in two distinct stages
light reactions (light-dependent reactions) : capture energy and convert it to ATP
dark reactions (light -independent reactions) : use ATP to synthesize organic compounds & involves carbon fixation
many variations found in approaches
oxygenic and anoxygenic