Lecture 13 and 14 Electron Transport Chain and Oxidative Phosphorylation

does the electron transport chain use oxygen

yes

how does the ETC produce ATP

through a gradient and oxidative phosphorylation

where does the ETC take place

in the inner mitochondrial membrane

what are the layers of the mitochondria

the outer layer and the inner layer

what is the outer layer of the mitochondria like

flat

what is the inner layer of the mitochondria like

goes up and down, creates crevices which increase surface area, allows proteins to sit on them

mitochondria anatomy from outside to in

• Outside mitochondria is cytosol

  • Then outer membrane

    • Then inner membrane

      • Then intermembrane space

        • Then mitochondrial matrix

what is the glycerophosphate shuttle

pathway to get the NADH out in the cytosol into the ETC through FADH2

inner membrane between matrix and outer membrane

a highly folded, protein-rich inner membrane separates the mitochondrial matrix from the outer membrane

what are required move reducing equivalents, ADP, and Pi into the mitochondria

transport proteins

where does the ETC occur

inner mitochondrial membrane (folded)

significance of the location of the ETC

it has access to the mitochondrial matrix and the intermembrane space

what makes up the ETC

4 complexes and 2 electron carriers (ubiquinone [Co Q] and Cytochrome C)

what occurs at complex 1

NADH gets oxidized to NAD+, produces electrons and protons → electrons released to Co Q and 4 protons into the intermembrane space (4/NADH)

what occurs at complex 2

FADH (that is produced from succinate → fumarate in TCA) gets oxidized → electrons get released to Co Q, 0 protons produced

what does Co Q do

takes 2 electrons from either complex 1 or 2, transfers them to complex 3 (does not matter where the e- are from)

what does complex 3 do

takes electrons from Co Q and transfers them to cytochrome C → produces 4 protons into the intermembrane space

what does complex 4 do

cytochrome C gives the electrons to complex 4, which gets the electrons to oxygen → oxygen becomes H2O and 2 protons are released into the intermembrane space

what is the final electron acceptor in the ETC

oxygen @ complex 4

what does complex 5 do

ATP synthase is run when there are 10 protons, produces 2.5 ATP when NADH is present, 6 protons from FADH2 produce 1.5 ATP

what is coenzyme Q

one of the most antioxidants because it accepts electrons, you need to accept electrons in this process or otherwise they leak out of the system and interact with the oxygen to produce reactive oxygen species

what can occur in the ETC and oxidative phosphorylation steps in bacteria

once you reach Co Q, the process can go to terminal oxidase or follow the pathway higher organisms do

what are the inhibitors to ETC

naturally occuring toxins that either target complex 1, 3, or 4

what inhibits complex 1

rotenone or amytal → blocking this complex drastically reduces the ability to produce ATP, but the ETC can still happen through complex 2

what inhibits complex 3

antimycin A → negates the ETC because you cannot get to cytochrome C

what inhibits complex 4

cyanide (CN-) → the worst possible cause because it completely shuts down the ETC

what does stigmatellin do

bacterial toxin that blocks a particular site on CoQ which stops it from being able to take on more electrons, shuts down the ETC

free energy of ETC from NADH to O2 can drive the synthesis of

~ 2.5 ATP

how are the electron carriers arranged

• Electron carriers are arranged in the mitochondrial membrane so that electrons travel from complexes I and II via coenzyme Q to complex III, and from there via cytochrome c to complex IV

complex 1 summary

The L-shaped complex I transfers electrons from NADH to CoQ via a series of iron-sulfure clusters and translocates four protons to the intermembrane space

complex 2 summary

Complex II transfers electrons from succinate to the CoQ pool but does not contribute to the transmembrane proton gradient

complex 3 summary

Electrons from complex III are transferred to cytochrome c and two protons are translocated during the operation of the Q cycle in complex III

complex 4 summary

Complex IV accepts electrons from cytochrome c to reduce the O2 to H2O and translocates four protons for every two electrons transferred

protons from the ETC

have the potential to produce ATP

what happens when you have a high H+ gradiant in the intermembrane space

the protons want to go back into the matrix because things move from high to low conc → complex 5

complex 5 overview

not part of the ETC, aka ATP synthase, subunits of complex 5 turn and produce ATP, for every 10 protons → 2.5 ATP produced

overview of the binding change mechanism

3 different conformations in the subunit, the 3 parts can change into all 3 conformations, but at a single point they each are only one, moves counterclockwise

energy to make ATP comes from the H+ gradient, tight conformation is always bound with ATP, each time it rotates, it produces 3 ATP

mechanism of binding change ATP synthase

1. ADP + Pi is added to loose part

2. Energy comes from H+ rotation, allows conformation change 

   1. Tight becomes open, open becomes loose, and loose becomes tight

      1. Everything moves counterclockwise

3. ATP is now bound to open, getting released into the matrix

Loose becomes tight, ADP + Pi → ATP

chemicals and oxidative phorphorylation becoming uncoupled from the ETC

• Chemicals can be introduced to allow H+ to move between the cytosol and matrix

  • Produces no usable ATP

• 2,4-DNP is a weight loss drug that is toxic and uncontrollable

  • It breaks down food but causes a diminish in the amount of ATP

uncoupling in brown adipose tissue generates heat

• Aka the chemiosmotic theory

• Proton gradient keeps animals warm by running H+ through UCP1, generates heat and allows for hibernation

H+ gradient can

• Drive UCP1 to keep an animal warm

• Run ATP synthase to produce ATP