Lecture 22 Flashcards
what does the electron transport do
makes a proton gradient across the inner membrane
what does the mitochondria convert reduction potentials too
proton gradient then into ATP
protons per complex 1, 3,4
1- 4
Q-4
4-2
what does electron microscopy suggest about the complexes
they are “supercomplexes” referred to as a respirasome
what is coupled with the proton gradient
ATP synthesis
E- cant flow if the pH gradient is what
too steep
what to chemical uncouplers do?
dissipate the proton gradient
ex: 2,4 DNP
FCCP
CCCP
DNP (dinitrophenol)
• Powerful “slimming” drug • >100,000 people treated in 1930’s • Converts fat directly into heat. • Very narrow therapeutic window. • Slight overdose causes catstrophic loss of energy in the body. – Excessive sweating, extreme thirst, cataracts, irreversible damage to heart, liver, lungs. – Ultimately paralysis, death. • First drug to be banned by FDA – 1938.
what inhibits the ATP synthase
oligomycin and venturicidin
How much ATP is made?
- Every NADH that enters complex I yields about 2.5 ATP
- Every FADH2 that enters complex II yields about 1.5 ATP
These numbers can change depending on how UNCOUPLEDthe mitochondria are.
Mitochondrial uncoupling
• Brown Fat generates heat
– Hibernating animals.
– Newborn infants.
– Lots of mitochondria in fat tissue makes it brown.
How is the energy in the proton gradient
captured to make ATP?
**AT.P Synthase **
Like an electric motor, ATP synthase.
stationary parts and rotating parts
γ-subunit
coiled-coil inserts into the central cavity of the α3β3 complex γ-subunit coiled-coil is asymmetric
Stator + αβ-subunits
do not rotate
what drives the rxn
Protonation and Re-ionization of a
glutamate in c-ring subunits
• The c-ring rotates next to the a-subunit
• The a-subunit & c-ring provide a path for H+ to
cross the membrane
• 2 half-channels in the a-subunit & glu residues in c-ring subunits
what drives the conformational changes
Rotation of the γ-subunit drives Conforma@onal Changes in the αβ subunits Interconvert between Tight, Loose, and Open conformations
how many atps does one full rotation of y subunit produce?
3
The β-subunits are the catalytic subunits.
Substrate binding sites are at the α/β subunit interface
The γ-subunit rotates, the αβ-subunits do not.
ATP Synthase: The movie
As it rotates, the asymmetry of γ-subunit coiled-coil
drives sequential conformational changes in the α3β3 complex between Tight, Loose, and Open conforma@ons, synthesizing ATP from ADP and Pi
The γ-subunit is tightly coupled to the c-ring. A path for protons across the membrane is provided by channels in the a-subunit and the protona@on and reionization of glutamate residues in the c-ring subunits.
The ATP synthase is BIG, it dimerizes and helps fold?
cristae
How much ATP is made
- How many protons pumped per NADH?
- 10 protons
- How many protons per ATP synthase cycle?
- 8 protons / 3 ATP = ~2.7 protons / ATP
- for 10 protons (1 NADH) expect even more ATP
• Co-transport systems that move ADP & Pi into the mitochondrial matrix and ATP out use some of the energy stored in the proton gradient
experimental atp produced
Every NADH that enters complex I yields about 2.5 ATP
Every FADH2 that enters complex II yields about 1.5 ATP
Glucose to lactate yields ATP
Glucose to CO2 yields ATP
2 ATP
32 ATP
Pyruvate to Acetyl CoA
(per mole pyruvate)
ATP, NADH, FADH2?
ATP= 0 NADH= 1 FADH2= 0
citric acid cycle (per mole pyruvate)
ATP, NADH, FADH2?
ATP= 1 NADH= 3 FADH2= 1
Total/mole pyruvate
ATP, NADH, FADH2?
ATP= 1 NADH= 4 FADH2= 1
Total/mole glucose mitochondria
ATP, NADH, FADH2?
ATP= 2 NADH= 8 FADH2= 2
Glycolysis (per mole glucose) cytoplasm
ATP, NADH, FADH2?
ATP= 2 NADH= 2 FADH2= 0
ATP, NADH, FADH2?
ATP= 0 NADH= 1 FADH2= 0
Overall total/mole glucose
ATP= 4 NADH= 10 FADH2= 2
Key concepts for Oxidative Phosphorylation
- Respiratory chain pumps protons across the inner mitochondrial membrane.
- Uncouplers and inhibitors of ATP synthase can influence oxygen consumption.
- ATP synthase functions as a rotary motor with three active sites and a ring that moves as it binds and releases protons.
