Where does ATP synthase derive energy to produce ETC

• outer membrane has pores that many compounds can pass thru (except proteins)
• inner membrane encloses matrix
• space btw two membranes is intramembrane space
• inner membrane is very impermeable (only NH3 and CO2 can diffuse thru while everything else needs a transporter)
  • needs lots of protein

NADH + H + 1/2O2 → energy (in small packets) + NAD + H2O

• NADH dehydrogenase (flavoprotein-FMN that can accept H from NADH)
• cytochromes (a, a3, b, c, c1)- they can undergo oxidation and reduction that is freely reversible
• CoQ
• non heme iron proteins (Fe-S clusters)

ALLOWS FOR ENERGY TO BERELEASED IN SMALLER PACKETS!!!!!

ALL HAVE DIFFERENT REDOX POTENTIALS

• three Fe-S clusters
  • one with two Fe and two S
  • another with four Fe and four S
• two of the three clusters have Fe coordinated to protein via thiol gropu of Cys and inorganic sulfur
• if you trate with acid, the Fe and S will be released

• undergo redox rxn via one electron at a time or a pair of electrons at a time
• very hydrophobic
• freely soluble in inner mitochondrial membrane
  • can move around in the lipid portion of the membrane
• called ubiquinone

Describe complex 1 of ETC

• called NADH-CoQ oxidoreductase 
• contents (46 different proteins)
  • NADH dehydrogenase (flavoprotein)
  • many Fe-S cluster proteins
• function- pass electrons of NADH to CoQ
• NADH binding site located on matrix side of inner mitochondrial membrane
  • cytosolic NADH cant interact with complex I

• transmembrane dimer within inner mitochondrial membrane
• contents
  • cyc c1- peripheral protein associated with IM membrane on inner membrane space side
  • cyc b
  • Fe/S cluster proteins
• function- pass electrons from CoQ-H2 to cyc c
• called CoQ-cyc c oxidoreductase

• transmembrane protein
• contents
  • cyc a
  • cyc a3 (binding site for oxygen)- unlike other globin proteins, has "top" of Fe bond that is never occupied (ligand not sitting on top)
  • two Cu centers
• function- pass four electrons from reduced cyc c to molecular oxygen to form two molecules of water
• called cytochrome oxidase
• oxygen binding site on matrix side of membrane

• transmembrane
• contents
  • F1- the head
    • 3 alpha (do not move)
    • 3 beta (do not move)- have binding units for synthesis of ATP
    • gamma (shaft in btw alpha, beta)
    • delta
    • epsilon
  • F0- the body
    • a protein (proton pump)
    • b2 protein
    • c protein (8-10 proteins that make up a circle)
      • in the center of each c protein is Asp
      • acts as a rodor
      • binds to epsilon and gamma units and spins with c as the rotor
• alpha, beta, delta, b2, a subunits anchored to inner mitochondrial matrix

• uses energy generated from oxidation of NADH and the reduced flavins to drive synthesis of ATP from ADP and P
• F1 contains ATP synthase activity

Where do we make most of our ATP within the mitochondria

• make the ATP in the matrix, so we need a way to get it out to the cytosol (ATP/ADP translocase)

• very abundant in inner mitochnodrial membrane
• acts as antiport (ATP is moved out of matrix, ADP moved into matrix)
  • need to do as antiport

• membrane bound enzyme complex
• binding sites on matrix side
• pass electrons from succinate to CoQ
• called succinate dehydrogenase
  • make fumarate from succinate
  • creates FADH2
  • passes electrons to Fe/S cluster
  • Fe/S cluster will pass electrons to CoQ

• membrane bound enzyme complex
• function- pass electrons from fatty acyl-CoA to CoQ
• first enzyme in beta oxidation
• mech of action
  • fatty acyl CoA produce fatty enoyl CoA
  • creates FADH2
  • goes to electron transfering flavoprotein
  • transfer to Fe-S cluster to transfer electrons to CoQ

• associated with inner mit. membrane
• attached to cytosolic side of membrane
• function- pass electrons from GP from CoQ
• mechanism of action
  • alpha glycerol phosphate goes to DHAP
  • creates FADH2
  • pass directly to CoQ

Mechanism of action of uncoupling

UCP 1 (thermogenin)

UCP 2

UCP 3

With each complex, how many protons are pumped for every one NADH

• I- four protons
• II- two protons
• III- four protons

cyanide

rotenone

• translocase slow down
• decrease ADP in mit, so ATP synthase slows down (no proton pumping)
• H's are not pumped into cytosol, so NADH/NAD ratio increase
• shuts down dehydrogenases

• energy status of cell (ratio of ATP/ADP)
• availability of substrates
  • oxygen can be rate limiting in times of exercise

• all the complexes have their active portions reduced
• this leads to slow down/shut down (electron back up)
• this means you cant pump protons
• ATP production will eventually slow down because we cant maintain the gradient
• Net result: go into anaerobic conditions

• binds to cyc a3 when the Fe is in the +3 oxidation state
• clinical app.- treat by oxidizing Hb to Fe 3+ to sacrifice some Hb so complex IV in ETC can keep working

• block translocase

• eliminate complex I
  • increases in NADH\

• they prevent a lot of the hydrogen produced by ETC from going through complex, and it basically disipates the gradient so that energy can be used as heat
• allowing ATP production