Week 7 Flashcards
Energy Production: Chemoorganotrophs
Glucose: glycolysis, entner doudoroff
lipids: C.A.C
proteins: enter from glycolysis or C.A.C
ETC and PMF
High ATP
Anaerobic Respiration
Occurs both oxic and anoxic
oxic = O2 terminal electron acceptor
Respiration of e. coli
No complex III, conserves less energy, exch 8 H+ for every 2 electrons
No O2 and nitrate: used nitrate reductase as terminal reductase, less energy, 6 H+
Chemolithotrophy
Inorganic chems as electron donors, begins w/ oxidation of inorganic electron donor, electrons enter ETC.
ex. H2S, H2, Fe, NH4
Who depends on oxidative phosphorylation and what’s the gain?
Both chemoorgano (heterotrophs) and chemolitho (autotrophs, CO2 CS) Aerobic or anaerobic. Difference is source of cellular carbon. Chemolitho use reverse electron transport
Energy Production: Chemolitho
Biogeochemical cycling
1. oxidize hydrogen
2. oxidize NH4 to nitrate
3. sulfur oxidizing microbes
CO2 = macromolecules
NADH reducing power
Chemolitho reducing power
NADH is reducing power
Obtained by:
1. directly from inorganic molecule
2. from reverse electron flow in ETC
H2 Oxidizing Bacteria
Membrane hydrogenase involved in energy generation
Cytoplasmic hydrogenase provides reducing power directly from inorganic molecule
Nitrifying bacteria
Nitrogen cycling via nitrification
Req 2 diff genera
Oxidize NH4 in two steps aerobically
1. Nitrosomonas
2. Nitrobacter
Nitrobacter in ETC
When atp needed: forward etc and creation of pmf
reducing power NADH from reverse ETC
Sulfur-oxidizing bacteria
Insoluble, ext. sulfur attach themselves to crystals to oxidize elemental sulfur via membrane/periplasmic proteins
Oxidize H2S, elemental sulfur (S0) and thiosulfate (S2O3) to sulfate
Sulfur oxidizing bac, how are energy rich compounds synthesized?
- oxidative phosphorylation
- substrate-level phosphorylation
APS reductase
Energy Production: Phototrophy
E from light trapped and converted to chem energy (ATP, NADH, NADPH)
Typically also Autotrophs
2 Part Process for photoautotrophy:
- Light reactions: capture light with pigments and convert to ATP (phototroph)
- Dark reactions: ATP used to reduce CO2 and synthesize cell constituents (autotroph)
Phototrophic Pigments
Organisms must produce some form of chlorophyll (or bacteriochloro) to be photosynthetic
Chlorophyll related to porophyrins, single Mg atom to 4 planar rings, diff func groups = diff chlorophyll
Chlorophyll light absorption
Mid 600s nm and low 400 nm, green light transmitted. Different chlorophylls = diff absorption spectra
What chlorophylls do cyanobacteria, prochlorophytes, and anoxygenic phototrophs produce?
CB: chlorophyll a
PCP: chlorophyll a and b
AOXP: bacteriochlorophylls
Where is chlorophyll located in eukaryotes and prokaryotes?
Eukaryotes: thylakoids
Prokaryotes: No chloroplasts, diff systems include: cytoplasmic membrane, membrane invagination, chlorosomes, thylakoid membranes
Carotenoids;
Where? What do they do?
Firmly embedded into phototrophic membranes
Absorb diff wavelengths of light, yellow, red, brown, or green. absorb blue light.
Can also act to protect bacteria from oxidizing sunlight.
Phycobiliproteins;
Where? What do they do?
In CyB + red algae, tetrapyrroles bound to proteins, form aggregates called phycobilisomes, allow cell to grow at low light
How is chlorophyll and accessory pigments arranged?
Arrays called antennas; large surface area to maximize photon capture
Where is captured light transferred?
To reaction centres, conversion of light to ATP
What is the Photosystem?
antenna and its associated reaction-centre chlorophyll.
Electron flow to PMF to ATP
Definition of phototrophy and the 3 types
Use of light energy to fuel cellular activity
- Anoxygenic photosynthesis
- Oxygenic
- Rhodopsin-based
All ATP MADE
What does phototrophy generate with light?
PMF.
ATP synthase makes ATP by phosphorylation. Oxygenic or anoxygenic.
Purple bacteria info. Phototrophy.
Anoxygenic. Common in anoxic aquatic environ.
Light into chem energy. PRC.
RC contains photopigments, they absorb light, trans E to PRC, forms PMF that ATP synthesis.
What happens to electrons in purple bacteria?
They are returned. cyclic photo phosphorylation
Phototrophy; What’s required to reduce power? Where does it come from? How?
NADH required to produce cell material.
Can come from variety of e- donors (H2S ex)
Reverse electron transport. (from quinone pool backwards to reduce NAD to NADH)
Examples of mostly obligate anaerobes. E source?
Purple bacteria, Heliobac (G+), acidobac.
E source is something other than H2O. O2 not produced.
Anoxygenic photosystem. What’s involved? e- transport? Held in place?
Photosystem involves bacteriochlorophyll.
Occur in reaction centre
LMH Polypeptides.
Two light reactions?
Photosystem I and II
Oxygenic photo: Atp production?
Non-cyclic or cyclic phosphorylation
What happens in noncyclic electron flow? oxyphoto
PSII becomes active
ATP + NADPH made
What happens in cyclic e- flow?
ATP made
Only PSI active
Bacteriorhodopsin based phototrophy
some arch and bac use rhidopsin
membrane protein which functions as a light driven proton pump
synthesis of atp by pmf and atlases
etc not involved
halobacterium salinarum
halophilic archaea
normally chemoorgano
makes bacteriorhodopsin under high light and low O2
O2 not soluble in high salt environment
phototrophic until o2 level increases
Amphibolic pathways
reaction pathways that utilize roles of both catabolism and anabolism
operate simultaneously, independent
important examples: glycolysis, pentose phosphate pathway, CAC
Metabolism control (3) mechanisms
- transcriptional/translational regulation of enzymes (pos + neg regulators, mrna lifetime)
- metabolic channeling, diff local of enzymes and metabolites, compartmentalization
- post translational regulation, occurs to enzyme after syn
Allosteric regulation
happens with most regulatory enzymes
activity altered by small molecule (effector), bonds non covalently at regulatory site, changes shape of enzyme and alters activity of catalytic site
Covalent modification
reversible on and off switch
addition or removal of a chemical group
advantage is being able to respond to more stimuli in varied and sophisticated ways
Cell can use these to manufacture all of its needs
precursor metabolites
Anabolism
biosynthesis of cellular macromolecules, C and N required
Nitrogen fixation
2 Proteins in complex
Reaction catalyzed by nitrogenase complex
dinitrogenase reductase (rapidly inhibited by O2)
dinitrogenase
Sulfur’s necessities
Syn of amino acids cysteine and methionine. Syn of coenzyme A and biotin.
Sulfur reduction pathway
Sulfate activated by ATP
formation of PAPS intermediate
reduced to sulfite
further reduced to h2s, added to serine to make cysteine
5 CO2 fixation pathways
- calvin cycle
- reverse cac
- hydroxypropionate cycle
- acetyl-coa pathway
- 3 hydroxylpropionate/4-hydroxybutyrate pathway
calvin cycle
most common autotrophic pathway to fix Co2
6 co2 to one molecule glucose
Calvin cycle phases: (3)
- Carboxylation phase
catalyzes co2, 6 carbon to 2 phosglyc - reduction phase, 2atp 2nadph consumed, reverse glycolysis
- regeneration phase, ribulose 1,5 regeneration, another atp consumed
