Ch 14.1-14.3 (Book) Flashcards
microbes transfer energy by moving _______
electrons
pathway of electron flow
reduced food molecules –> energy carriers –> membrane protein cytochromes –> oxygen or oxidized minerals
3 major classes of metabolism that use an ETC
organotrophy (organic e- donors)
lithotrophy (inorganic e- donors)
phototrophy (light absorption excites e-)
electron transport system/chain
a series of membrane-soluble carriers
converts energy into an ion/electrochemical potential btw 2 compartments separated by a membrane
what happens in an ETS
e- are accepted from an initial e- donor
the ETS proteins/cofactors act sequentially as e- donors and acceptors to transport the e- to a terminal e- acceptor
proton pumping is coupled to the oxidation-reduction rxns
metabolism using an ETS is classified based on what
the nature of the initial e- donors and terminal e- acceptor
organotroph/chemoorganotroph
organic molecules donate e-
called respiration if a terminal e- acceptor is reduced
lithotrophy/chemolithotrophy
inorganic molecules donate e-
facultative or obligate
phototrophy
light capture by chlorophyll
couple photolysis to CO2 fixation for biomass (absorb light to make ATP and couple to biosynthesis)
reduction potential (E)
tendency of a compound to accept electrons measured in volts or millivolts
a positive deltaE has a _______ deltaG
negative
gain of e- releases energy
redox couple
the oxidized and reduced states of a compound
standard reduction potential Eprime
1M concentration
pH of 7
how are deltaGnotprime and deltaEnotprime related
deltaGnotprime = nFdeltaEnotprime
n = number of e- transferred
F = Faraday’s constant 96.5 kJ/V*mol
calculate E using Enotprime
E = Enotprime - (2.303RT/nF)(log[products]/[reactants])
where is a bacterium’s ETS located, and gram-neg?
cytoplasmic membrane
gram-neg: inner cytoplasmic memb (separates cytoplasm from periplasm)
why isnt the outer membrane of gram-neg used for the ETS?
it is permeable to protons and therefore can’t store energy
where are the ETS proteins in mitochondria?
in the folds of the inner mitochondrial membrane called cristae
separates inner mitochondrial space from the intermembrane space
how were cytochromes named
for their deep colors
in prok where are cytochromes usually found
inside the cell membrane
oxidoreductases
name for ETS proteins b/c they oxidize one substrate and reduce another
ex. cytochromes and non-cytochromes
the sequential transfer of e- from one ETS protein to the next yields _______ for _______ _______
energy, proton pumping
proton motive force
H+ difference and the charge difference across the membrane
drives ATP syn, flagella rotation, nutrient transport
what two things make up a proton potential (delta p)
H+ concentration difference (delta pH)
charge difference (delta Y)
in pathogens what does the proton potential drive
multidrug efflux pumps
resistance to antibiotics
chemiosmotic theory
the energy from e- transfer between membrane proteins is used to pump protons
H+ accumulate outside the membrane
electrical potential (delta Y)
separation of charge
for bacteria: -50 to -150 mV
pH difference (delta pH)
log ratio of external to internal [H+]
if outside pH is 7.5 and inside is 6.5 the delta pH is 1 and the ratio of inside to outside H+ is 10
delta pH of 1 = proton potential of -60mV
what else influences delta p (proton motive force)
presence of other ions like Na or K
metabolic generation of acids from fermentation
can the gradient of other ions drive ATP synthesis?
yes, Na+ gradient in V. cholera has a Na+ dependent ATP synthase
uncoupler
a molecule that uncouples electron transport from ATP synthesis
cell take up both charged and uncharged forms
toxic b/c dissipates proton gradient
what happens in the respiratory ETS system
a series of carrier molecules harvests the reducing potential of e- in steps
classic ex: NADH/FADH2 transfer e- to O2
________ allow small energy transitions
cofactors
cofactors
small molecules that associate with the protein
ex. heme associates with cytochrome c
4 examples of cofactors
heme
FMN - flavin mononucleotide
uniquinone
iron-sulfur complex
quinones special
when reduced, move laterally in the memb. to transfer e-
3 functional componenets of a respiratory ETC
initial substrate oxidoreductase
mobile electron carrier
terminal oxidase
oxidation of NADH and reduction of Q –> QH2 in ETC provides energy to pump _ H+
4
can be 4 Na+ in some organisms
quinone pool
refers to all quinones and quinols
receive 2 e- and 2 H+ and transfer to a reductase
function of terminal oxidase
receive 2 e- from a quinol and transfers them to a terminal e- acceptor
do bacteria have alternate oxidoreductases?
yes, allows them to adapt to envir conditions like low O2
mitochondrial respiration
4 complexes with more subunits than in bacteria
pumps more protons than bacterial ETC
F1F0 ATP synthase
highly conserved complex in bacterial cell memb, mitochondrial inner memb, chloroplast thylakoid memb.
F0 in memb. lets protons in
F1 in cytoplasm makes ATP
how many protons in F0 = 1 ATP from F1
3 H+ = 1 ATP
can F1F0 go in reverse?
yes if ATP is high
which extreme bacteria use a sodium motive force
halophilic
