Proton Motive Force Flashcards
*Understand the concept of the “chemiosmotic hypothesis” and the ability of the “proton-
motive force” to produce ATP.
Chemiosmotic hypothesis- suggest that electron transport and ATP synthesis are coupled by proton gradient across mitochondrial membrane
The unequal distribution of protons (in gradient) drives the PROTON MOTIVE FORCE (allow ATP synthase to make ATP).
*Understand the reason for and the process of the “glycerol 3-phosphate shuttle”.
Since NADH cannot simply pass through mitochondria by itself (inner mitochondria, not permeable to NADH, NAD+), it’s electrons will use a shuttle to enter mitochondria.
Glycerol 3 phosphate shuttle used for electrons (from cytoplasmic NADH) to enter ETC (Electron transport chain) in MUSCLE
electrons transfer from NADH to FADH2 to Q and then to QH2.
when cytoplasmic NADH uses glycerol shuttle it makes 1.5 ATP since its carried through FAD.
*Understand the reason for and the process of the “malate-aspartate shuttle”.
Malate-aspartate shuttle used in HEART AND LIVER to bring electrons from cytoplasmic NADH to generate mitochondria NADH
Why: oxaloacetate does not readily cross mitochondrial membrane (need malate to cross inner mito, and covert oxalo to aspartate)
malate-aspartate shuttle consist of two membrane transporters, and 4 enzymes.
*Know what the “ATP-ADP translocase” transport protein does.
The ATP-ADP translocase enables exchange of cytoplasmic ADP for mitochondrial ATP.*
ADP must enter mitochondria for ATP to leave.
Translocase powered by proton-motive force.
*When ATP is synthesized, translocase move ATP out of mitochondria; cytoplasm now clutch on to ADP and then eversion occur (flip proton structure down) and ADP enter mitochondrial matrix.
*Understand why there is such a large difference in ATP yield from the complete oxidation
of glucose versus simple glycolysis (table 21.1)
Total of 30 ATP formed by complete combustion of glucose
-26 ATP formed in Oxidative phosphorylation
4 ATP from glycolysis- as metabolism of 1 glucose will create 2 molecules of pyruvate (net of 2 from glucose to pyruvate in glycolysis)
2 ATP from citric acid cycle (succinyl coa)
glucose under goes fermentation (lactate forming), only 2 atp generate per glucose.
*Understand the nature of uncoupling oxidative phosphorylation to produce heat.
If the Electron transport is uncoupled from ATP synthesis, heat is generated in process called non-shivering thermogenesis.
done through uncoupling protein 1 (thermogenin, integral mem protein of inner mitochondria)
uncoupling occurs in mitochondria in brown fat, where uncoupling protein transports protons form intermembrane space to mitochondrial matrix (flow through uncouple protein to matrix)
*Know where the following inhibitors affect the electron-transport chain; rotenone, amytal,
antimycin A, cyanide, azide and carbon monoxide.
Rotenone and AMYTAL block COMPLEX 1 (nadh-q reductase to go to QH2.)
Antimycin A blocks COMPLEX 3 (Q cytochrome c oxidoreductase to go to cytochrome c.)
Cyanide, Azide (N3-) and CO all block COMPLEX 4 (e from CYTC to go to O2.)
- Understand the nature of uncoupling electron transport from ATP synthesis. Why do some
individuals use “2,4-dinitrophenol” as a weight loss drug?
Uncoupling protein will uncouple proton gradient from formation of ATP. It will get rid of gradient and will release heat.
Dinitriphenol- uncoupler, formally used a weight loss drug. not used anymore because it would release a lot of heat in individuals (cause severe hypothermia).
uncoupler seen release a lot of brown fat commonly seen in newborns, descendants who lived in arctic.
Where in the mitochondria do you have lower concentration of H+ ions? higher concentration?
In intermembrane space- higher concentration of H+ ions
IN MATRIX- LOWER amount of H+ ions
What drives the spinning of the motor in ATP synthase?
The stored energy in the proton gradient drives the spinning of the motor.
Which part of mitochondrial membrane is impermeable to most ions? Which one is permeable?
INNER mitochondrial membrane- IMPERMEABLE to most molecules
outer mitochondrial- permeable to small molecules
What drives the synthesis of ATP?
The ATP synthase (motor) drives ATP synthesis.
What is the most common cause of mitochondrial disease?
disruption of complex 1 in ETC
defect in ETC reduces ATP synthesis, and increase amount of ROS, leading to mitochondrial damage
What are the kind of biological processes that proton gradients power?
Proton gradients power HEAT PRODUCTION, ATP SYNTHESIS, also flagellar rotation, active transport, NADPH synthesis
What are factors that inhibit Oxidative phosphorylation?
Blockers of ETC:
- inhibit ETC prevents oxidative phosphorylation, by inhibiting formation of proton-motive force.
- inhibit ATP synthase by inhibiting proton flow prevents Electron transport.
Uncouplers CARRY PROTONS across mitochondrial membrane:
- The ETC functions, but ATP synthesis does not occur because the proton gradient can never form.
- inhibition of ATP-ADP translocase prevents oxidative phosphorylation.
