3.5 Flashcards
net equation - glycolysis through CAC
C6H12O6 + 6O2 + 10NAD+ + 2FAD + 4ADP + 4Pi —> 6CO2 + 10NADH + 2FADH2 + 4ATP + 10H+
electron transport chain/ATP synthesis
responsible for the bulk of ATP production
NADH and FADH2
key electron carriers in redox reactions
most of glucose’s energy is transferred in electrons to NADH and FADH2
oxidation of NADH
oxidation of NADH to NAD+ is highly exergonic
energy released as electrons from NADH and FADH2 are passed along the respiratory chain
electron energy release
in a series of reactions, each releases a small amount of energy that can be used to power an endergonic reaction
energy released from e- transfers is used to actively transport protons into the intermembrane space
exergonic e- transfers is coupled with endergonic H+ transfers
H+ transport
creates an electrochemical gradient across the inner membrane
[H+] innerspace > [H+] matrix
electrochemical gradient
potential energy (proton motive force)
enzyme complexes
four enzymes complexes (I, II, III, IV) are integral proteins contained redox centers
NADH –> complex I –> Q –> complex III –> cyt c –> complex IV
FADH2 –> complex II –> Q –> complex III –> complex IV
mobile electron carriers
shuttle electrons between the immobile large membrane proteins in the electron transport chain
ubiquinone (coenzyme Q)
cytochrome C
CoQ
small nonpolar molecule
lipid soluble
in inner mitochondrial membrane
cytochrome C
small soluble/peripheral protein
water soluble
in the intermembrane space
contains prosthetic enzymes
O2 (ETC)
acts as the final electron acceptor
complex IV
-accepts electrons from cyt c
-passes electrons to O2 in active site
catalyzes the reduction of O2 to H2O
O2 + 4H+ + 4e- –> 2H2O
pH
measure of the total proton concentration in solution
pH = -log[H+]
[H+] = 10^-pH
chemiosmosis
diffusion of protons back across the membrane is coupled to ATP synthesis by ATP synthase
oxidative phosphorylation
ATP synthesis is catalyzed by ATP synthase via reoxidation of electron carriers in the presence of O2
ATP synthase
acts as a molecular motor
is the same in all living organisms
Fo unit: transmembrane channel for H+ diffusion (due to proton motive force)
F1 unit: catalytic subunit for ATP synthesis and a rotor
couples the diffusion of H+ with the formation of ATP
converts the potential energy to kinetic, causing the rotor to rotate
energy created with NADH/FADH2
difference in initial electron energy between NADH and FADH2 results in different number of ATP produced
a pair of electrons from NADH produces ~2.5 ATP
a pair of electrons from FADH2 produces ~1.5 ATP
product of ETC
C6H12O6 + 6O2 –> 6CO2 + 6H2O + 32 ATP
28 ATP from ETC
Why is O2 used as an electron acceptor?
it is the best electron acceptor due to its high electronegativity
a large difference between the potential energy of NADH and O2 electrons generates a large proton motive force for ATP production
prokaryotic ETC
some prokaryotes use alternate electron acceptors under anaerobic conditions
