biochem exam 3 - oxidative phosphorylation -

unfortunately knowt glitched before I could finish metabolism on the other one so this is oxidative phosphorylation sorry buddies!

cellular respiration removes _____ to generate ____

high-energy electrons from carbon fuel molecules to generate ATP

The citrate cycle

removal of high-energy electrons from carbon fuels as NADH and FADH2

Oxidative phosphorylation

electrons reduce O2 to generate a proton gradient, which is used to synthesize ATP

chemiosmotic theory

the movement of protons across the membrane down their concentration gradient to generate ATP 

1. reduced substrate (fuel) donates E-

2. electron carriers pump H+ out as electrons flow to O2

3. energy of e- flow is stored as electrochemical potential 

4. ATP synthase uses electrochemical potential to synthesize ATP 

electron transport

electrons flow from electron donors (low reduction potential (bad E- acceptor)) to O2 (large reduction potential)

what is the final electron acceptor in the ETC

O2

ETC coupling

downhill exergonic electron flow is coupled to teh uphill transport of H+ across the inner mitochondrial membrane

Protein components of the ETC

H+ gradient is initiated by outward pumping of H+ from the mitochondrial matrix by complexes 1, 111, 1V

what is another name for the ATP synthase complex

complex 5

what does the ATP synthase complex do

inward flow of H+ through ATP synthase accomplished ATP synthesis 

3H+ results in 1 ATP 

Path of electrons from NADH in the ETC

electrons from NADH enter at complex 1, then flow to coenzyme Q, complex III, and complex IV

a total of 10 H+ are translocated

1- 4 H+ 

3- 4 H+ 

4- 2 H+

path of electrons from FADH2

enter at complex II, then flow to coenzyme Q, complex III, and complex IV. 

a total of 6 H+ are translocated

3- 4 H+

2_ 2 H+

complex I: NADH-ubiquinone oxidoreductase

NADH is oxidized in the matrix

the flow of 2 electrons is facilitated by the sequential arrangement of electron carriers

Energy from electron transfer is used to translocate 4 H+ into inter membrane space 

coenzyme Q is reduced to form QH2

complex II_ succinate dehydrogenase

TCA cycle enzyme 

catalyzes oxidation-reduction of succinate to fumarate 

coupled redox reaction generates FADH2

reduces coenzyme Q to QH2

moves 2 e- NO movement of H+

coenzyme Q

acts as the mobile electron carrier and transports electrons from complexes I and II to complex III

what is Ubiquinone reduced to 

Ubiquinone (Q) is reduced to ubiquinol (Qh2) 

complex III: Ubiquinone-cytochrome c oxioreductase

accepts electrons from QH2

reduces cytochrome c

translocates 4 H to inter membrane space 

cytochrome C

small protein in inter membrane that carries H+ from III to IV

complex IV: Cytochrome c oxidase

accepts 2 electrons total, one at a time

cytochrome c is oxidized, while oxygen is reduced water

2 H+ are translocated across the membrane for every oxygen atom reduced to H2O

site of generation of ROS

ROS

reactive oxygen species, that comes from complexes I and III

Proton Motive Force

the energy of electron transfer conserved in a proton gradient 

PMF (delta P) = Chemical gradient (delta pH) + charge gradient (delta epsilon) 

respirasome

sight of cellular respiration

the super complex containing complexes I, III, and IV. 

complex 2 is generally found free-floating within the membrane 

ATP synthase structure

made of two large structural components (FO *not zero, oh) and F1

Fo (a,b,c)

has a H+ channel embedded in the mitochondrial membrane

for rotary, ATP synthase of different organisms can have different number of carbon subunits (8-12) 

F1 (a3, b3, y, epsilon,)

has the catalytic sites and protrudes into the matrix 

ADP + P to ATP happens in b subunits, not alpha 

3 functional units of ATP synthase

Stator

Headpiece

Rotor

Stator of ATP synthase

two half proton channels in a subunits. 

immobile stabilizing arm made of b, d, h, and OSCP 

H+ channels in subunit a 

headpiece of ATP synthase

a3, b3

site of ATP synthesis 

3 active sites, one on each B subunit

where ADP turns to ATP 

rotor

y, e, subunits,

c subunit ring made up of 10ish subunits

y subunit connects F1 and Fo

Proton flow around C ring

H+ enter the half-channel from the inter membrane space → bind to a glue or asp residue on one of the c subunits → leave the c subunit through the matrix half-channel 

the proton motive force powers rotation of the c ring 

rotation of the c ring powers movement of the y subunit, which in turn alters the conformation of the b-subunits

3 diff conformation of the b subunit

O: open (empty, no substrate)

L: loose (captured substrate, but not yet formed product) 

T: tight (synthesized ATP)

how far does the b subunits have to turn

120 degrees, with every 120 degree turn, b subunit conformation changes from L → T → O →L

in yeast how many h required for a 120 turn

3 H+ required for a 120 degree turn

How much ATp from 1 NADH

2.5 ATP

how much atp from 2 FADH

1.5 ATP

how much atp for aerobic conditions total

32 ATP

how many atp for anaerobic conditions

2 ATP

Cellular defense strategies against oxidative damage by ROS

superoxide dismutase scavenges superoxide radicals by catalyzing their conversion into hydrogen peroxide and molecular oxygen 

catalase catalyzes the disputation of hydrogen peroxide into water and molecular oxygen

both are ubiquitous and efficient! both perform their reactions at near the diffusion limited rate