cell energy Flashcards
substrate level phosphorylation
conversion of ADP to ATP using a phosphate from a phosphorylated immediate
the latter being one of the substrates of the reaction
- involves phosphoryl group transfer to ADP
- transferred to ATP from a compound that is hydrolysed
mitochondria structure
sub-cellular organelles
found in cytoplasm of all eukaryotic cells
surrounded by a double membrane
inner
outer
matrix
inter-membrane space
inner membrane of mitochondria
folds called cristae
covered in elementary particles (bumps)
permeable to limited compounds
eg urea and glycerol
specific carrier proteins for others
enzymes for electron transport in membrane
outer membrane
smooth, freely permeable to small molecules
salts, sugars, ATP and NAD
matrix
fluid filled
contains enzymes for TCA cycle and B oxidation
contains mitochondrial DNA and RNA
inter membrane space
fluid filled
site of oxidative phosphorylation
oxidative phosphorylation
generation of ATP from ADP and inorganic phosphate via electron transport chain
what is the electron transport chain?
composed of a number of hydrogen and electron carriers
each carrier successively reduced and the oxidised as H or electrons passed between them
hydrogen carriers
coenzymes
coenzyme Q
flavin adenine dinucleotide
flavin mononucleotide
nicotinamide adenine dinucleotide
electron carriers
cytochromes
cyta
cyta3
cytb
cytc
cytc1
respiratory chain in etc
NADH
flavin mononucleotide
coenzyme Q
cytb
cytc1
cytc
cyta+a3
O2
what does the chemiosmotic hypothesis of mitchell depend on?
membrane impermeable to protons and other inorganic ions
but protons can be transferred across
chemiosmotic hypothesis of mitchell
protons move from matrix to inter membrane space
creates a proton gradient that needs to be dissipated
- done through transport of protons via ATP synthase back into matrix
ATP synthase synthesises ATP from ADP and inorganic phosphate
= ATP and water
protons gradient drives ATP synthesis via ATP synthase
generates energy to synthesise ATP
ATP synthase
require 3 protons to be transported through per ATP made
= 3 ATP per NADH
= 2 ATP per FADH
why is 3 ATP an overestimate?
protons used to transport ADP into matrix for phosphorylation
sometimes ATP used o transport NADH from cytoplasm into mitochondria
more likely net gain of 2.5NAD/1.5FAD
inhibitors of oxidative phosphorylation
antimycin A
cyanide and carbon monoxide
oligomycin
how does antimycin A inhibit oxidative phosphorylation?
antibiotic
inhibits etc at complex 3
used as an antibiotic as acts as a poison to bacteria
how does cyanide and carbon monoxide inhibit oxidative phosphorylation?
poisons
prevent final stage of etc by inhibiting cytochrome oxidase
how does oligomycin inhibit oxidative phosphorylation?
antibiotic
inhibits link between etc and phosphorylation of ADP to ATP synthase
used as an antibiotic as acts as a poison to bacteria
electron transport chain complex 1
NADH-CoQ reductase complex
flavin mononucleotide
NADH transfers 2 electrons to FMN
reduced to FMNH2
- accompanied by uptake of 2 H+ from matrix
FMNH2 transfers electrons to FeS clusters
- ferric reduced to ferrous due to accepted electrons
ferrous transfers electrons to CoQ
- CoQ reduced to CoQH2 - ubiquinol
delta g = 69.6kj/mol
enough to create ATP
- energy used to pimp 4 protons from matrix to space
electron transport chain - complex 3
CoQH2 cytochrome c reductase complex
3 cytochromes
- cytochrome b562
- cytochrome b556
- cytochrome c1
CoQH2 passes electrons to heme group of cytb
- reduces Fe3+ to Fe2+
cytb Fe2+ transfers its electrons to FeS cluster 3 complex
Fe2+ transfer electrons to heme group of cytc1
cytc 1 Fe2+ oxidised as it transfers electrons to heme group of cytc
electron transport chain - complex 4
cytochrome c oxidase
cytc Fe2+ transfers electrons to cyta
- reduces Cu2+ to Cu+
cyta transfers electrons from Cu+ to its heme group
cyta transfers electrons from heme group to cyta3
- reduces Cu2+ to Cu+
cyta transfers electrons via Cu+ to its heme group
electrons transferred from cyta3 heme group to oxygen
= water
= enough energy to pump 2 more protons across to space
electron transport chain - complex 2
succinate-CoQ reductase complex
succinate oxidised
= fumarate
catalysed by succinate dehydrogenase
- releases electrons which generate FADH2
FADH transfers electrons to the FeS cluster
- reduces Fe3+ to Fe2+
Fe2+S transfers electrons to CoQ
- reduces CoQ to CoQH2 - ubiquinol
etc for NADH and FADH
NADH = complex 1,3,4
FADH = complex 1,2,3,4
