Mitochondrial synthesis of ATP Flashcards
How many weeks’ worth of stored energy do we have on average?
4-6 weeks
How much ATP do you use every day?
Your body weight’s worth
How much of the energy in food is converted to ATP?
50%
What is the size limit for passage of molecules across OUTER mitochondiral membrane?
5000 da (Daltons)
What are the folds in the inner membrane of mitochondria called?
christae
Why is the inner membrane of mitochondria such a good electrical insulator?
capable of maintaining large ionic and electrical gradients
What are the two spaces in mitochondria called?
Matrix and intermembrane space
What is contained in the Matrix space?
contains wide range of enzymes – Krebs cycle, fatty acid oxidation, urea cycle (in liver)
high concentrations of substrates, cofactors & ions
contains mitochondrial DNA, RNA & ribosomes (these resemble bacterial components) though few mitochondrial proteins are coded on mitochondrial DNA
What is in the intermembrane space?
has metabolite & ion concentrations similar to cytosol
contains cytochrome c (electron carrier)
Where are mitochondrial proteins coded for?
In the nucleus of the cell
What is the link reaction?
Pyruvate dehydrogenase catalyses conversion to acetyl CoA
What is vitamin B1?
Thiamine
What is Wernicke-Korsakoff syndrome?
Lack of thiamine seen in alcoholics
neuro/cardio symptoms
Why is pyruvate dehydrogenase a key ‘decision point’ in metabolism?
Acetyl CoA cannot be converted back to glucose in humans
Conversion of pyruvate to acetyl CoA commits the C atoms of glucose to energy production or lipid synthesis
What are the main 2 stages of the Krebs cycle?
Synthesis of 6-C compound (citrate) which then loses 2 C as CO2 to become 4-C compound (succinyl CoA)
Oxidation of 4-C compound to regenerate oxaloacetate and initiate another round of the cycle
What are the main outputs of the Krebs cycle?
Reduced coenzymes NADH & FADH2 – electron carriers
CO2 – waste product
1 GTP = 1 ATP
What are the 3 key enzymes in the Krebs cycle?
citrate synthase
isocitrate dehydrogenase
α-ketoglutarate dehydrogenase
Why do patients with type 1 diabetes synthesise ketones?
In the absence of insulin, fatty acids are mobilised from adipose tissue and oxidised to acetyl CoA – acetyl CoA levels HIGH
But lack of oxaloacetate prevents acetyl CoA from entering the Krebs cycle
So ketones are synthesised instead
What two processes is oxidative phosphorylation made up of?
Electron Transport (oxidation)
ATP synthesis (phosphorylation)
What membrane proteins make up the electron transport chain?
Complexes I to IV
ubiquinone
cytochrome c
How does cyanide work?
Cyanide inhibits transfer of electrons from complex IV to oxygen
What happens to the energy released by electron transfer across complexes?
used to pump H+ ions into intermembrane space
For each pair of electrons from NADH, how many electrons are translocated?
10
This creates a large proton gradient across the well insulated inner membrane
What happens when the H+ ions move back down the concentration gradient into the mitochondrial matrix?
H+ ions flow through ATPase enzyme and help create ATP from ADP and Pi.
How many ATPs synthesised for pair of electrons from NADH?
2.5 ATPs
How many protons are required to synthesise 1 molecule of ATP?
4
Why won’t ATP synthesis work if electron transport isn’t working?
lack of reduced substrates or more commonly lack of oxygen - there is no proton gradient to drive ATPase enzyme
Why does electron transport stop if ATP synthesis is blocked?
Proton gradient builds up to the level where the complexes have insufficient energy to pump more protons across the membrane
(gradient too large)
Energy cannot be released from the electron carriers, so they can’t accept any more electrons
How do uncouplers work?
Weak acids, associarte with protons in intermembrane space and help prevent gradient from reaching stage where carriers can’t accept more electrons
What is the function of uncoupling in humans?
generate heat in newborns - non-shivering thermogenesis
