Mitochondrial synthesis of ATP Flashcards
what is the approximate concentration of ATP in cells
6mM
what is the turnover of ATP per day?
75kg/day
how much of the energy from food produces ATP?
around 1/2
what is the permeability of the outer membrane of mitochondria to substances?
freely permeable if
what is characteristic of the inner mitochondrial membrane?
cristae!
what does the inner membrane of mitochondria control?
entry/ exit of molecules
what sort of insulator is the inner membrane of mitochondria?
electrical insulator
by controlling movement of ions
what types of transporters are within the inner membrane of mitchondria?
more protein than lipid transporters
what is the concentration of metabolites and ions like in the intermembrane space of mitochondria?
similar to cytosol
what substances are found within the matrix of mitochondria?
lots of enzymes
high concentration of substrates, cofactors, ions
mitochondrial DNA, RNA, ribosomes (most proteins encoded on nuclear DNA)
where does the link reaction occur?
matrix of mitchondria
what happens to pyruvate in the link reaction?
becomes acetyl coA
what is the key decision point of the link reaction and why?
pyruvate dehydrogenase
what inhibits the link reaction?
high energy levels so high ratio of NADH: NAD and high ratio of ATP: ADP and high levels of acCOa
what happens to NAD in the link reaction?
reduced to NADH
which cofactor is required for pyruvate dehydrogenase?
B1/ thiamin
what does B1/thiamin deficiency result in?
neurological problems/ cardiovascular symptoms
in alcohol addicts –> Wernicke Korsakoff syndrome
where does the krebs/ citric acid cycle take place?
mitochondria matrix
what activates pyruvate dehydrogenase enzyme?
high levels of Ca signalling sudden demand for energy
which 3 enzymes are key to the krebs cycle?
citrate synthese, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase
what happens during stage 1 of the krebs cycle?
acetyl coA –> 6C citrate –> 4C succinyl coA + 2CO2
how many CO2 molecules are released in the 1st stage of the krebs cycle?
2 CO2
what happens during the 2nd stage of the krebs cycle?
oxidation of 4C compound –> oxaloacetate
what are the products of the krebs cycle?
3NADH, FADH2, 2CO2, GTP,
what percentage of cellular ATP is produced in mitochondria under aerobic conditions?
95%
what does the concentration of intermediates in the krebs cycle depend on?
other reactions in the cell
what are intermediates in the krebs cycle exchanged for?
other metabolic pathways
which pathways may use krebs cycle intermediates as building blocks?
anabolic/ synthetic pathways
why does ketone synthesis occur in DMT1?
glycolysis inhibited, low pyruvate
oxaloacetate and malate removed from the krebs cycle to be used in gluconeogenesis
fatty acids oxidised for energy –> XS acteyl CoA because of lack of oxaloacetate therefore broken down into ketones –> ketoacidosis
which 2 processes are tightly coupled in oxidative phosphorylation?
electron transport and ATP synthesis
what happens during electron transport?
oxidation
what happens during ATP synthesis?
phosphorylation
what does the electron transport create?
proton gradient
what does ATP synthesis require?
proton gradient
which 2 cofactors are involved in electron transport?
NADH and FADH2
what supplies energy to electron transport?
electrons
what supplies energy to ATP synthesis (in oxidative phosphorylation?
proton gradient
how many complexes are involved in electron transport?
4 (I, II, III, IV)
which complexes are transmembrane?
I, III, IV
what are the 2 other electron carriers in the membrane needed for electron transport?
ubiquinone, cytochrome C
which complex does NADH give an H to?
complex I
which complex does FADH2 give H to?
complex II
what is the final electron acceptor of the electron transport chain?
oxygen
what happens to oxygen in the electron transport chain?
combines with electrons and 2 protons –> water
where does cyanide inhibit electron transport?
blocks the reduction of oxygen to water
where does oxidative phosphorylation occur in the mitochondria?
across the inner mitochondrial membrane (well insulated membrane)
where is the concentration of H lower in mitochondria?
in the matrix
which complexes translocate H across the membrane?
I, III, IV
which direction are H ions translocated?
from matrix into intermembrane space
how many H are translocated per NADH?
4
why does FADH2 cause fewer H to be translocated?
it releases electrons into the electron transport chain later than NADH
What does the F0F1 ATPase do?
synthesises ATP
What is the name of the antiporter that transports ADP and ATP?
adenine nucleotide transporter
Which other transporters exists in addition to F0F1ATPase and adenine nucleotide transporter?
Pi and H
how many H move through ATPase?
3
why does the movement of H down the conc gradient cause ATP to be produced?
it causes physical movement pushing the proteins around like a motor
which direction does ATP move through the antiporter and why?
matrix into intermembrane space so ATP can be released and used!
Why does one H move through the transporter as one Pi moves into the matrix?
to maintain electroneutrality as Pi is negatively charged
why can ATP synthesis not occur without electron transport?
electron transport required to set up the proton gradient
why might there be a problem with ATPase?
lack of ADP
why might electron transport be inhibited?
lack of oxygen or reduced cofactor substrates
why does a problem with ATPase stop electron transport?
H concentration builds up in intermembrane space so H can move down concentration gradient through complexes
how many H move across the inner mitochondrial membrane to the matrix per 1 ATP synthesised?
4 (3 through synthase 1 through H transporter)
what are uncouplers?
weak acids
what happens in uncoupling?
uncouple oxidation from phosphorylation
what effect do uncouplers have on the H gradient?
dissipates
what happens to electron transport and ATP synthesis?
electron transport can continue but ATP synthesis inhibited
which natural uncoupler protein exists in mitochondria in brown adipose tissue?
thermogenin
what is energy released as in brown adipose tissue?
heat
what activates thermogenin in brown adipose tissue?
decrease in core body temp, increase in NA released, increase in fatty acids in cytosol, activates thermogenin
