Bioenergetics 5: Electron Transport Chain Flashcards
Where is ETC in eukaryote vs bacteria
The mitochondrial inner membrane vs in the cell membrane of the bacteria
What is a respirasome
Its a supercomplex made of complex 1,3 and 4 all together- example of hand on mechanism where e are passed along to the one next to it. It has cytochrome and Q10.
How do electrons flow from NADH to Q in complex 1
NADH binds, electrons transferred to FMN (flavin mononucleotide), then through a wire of Fe-s complexes by process of electron tunneling.
The e eventually go to Q10 where it is reduced and carries the e- away.
How do electrons flow from FADH2 to Q in complex 2 (succinate)
As Succinate is oxidised to Fumarate, the electrons reduce FAD making FADH and then they are passed down the Fe-S complexes and then a haeme group which passes them to Q10 to reduce it. Q10 leaves
Whats difference in energy of NADH vs FADH2 and what does this mean for pumping
NADH has 1.135 V whereas FADH2 has 0.815 or redox potential. As a result complex 2 cannot pump H+ across the membrane. However C2 is faster than C1, due to smaller size and is more abundant in rats needing energy.
How does complex 1 physically pump protons (structure) and how many H+ per NADH
This flow of electrons changes the conformation of the transmembrane helices in the foot. The orientation of these helix gates changes to face the matrix where H+ bind to amino acids. Removal of Q means that means the helix gates go back to original conformation and pushes the H+ against the proton gradient. (matrix to intermembrane space)
It pumps 4 H+ per NADH.
What is electron tunneling
It is the transfer of electrons where electrons skip from successive irons across miniature distances that are highly conserved.
What is Q (10/0) Co enzyme Q what does it do, what forms does it exist in
Ubiquinone is a lipid soluble (not a protein) co enyzme. They carry 2 electrons and 2 hydrogens on the ketone groups to become the alcohol ubiquinol. Or they can only carry 1 H+ + e to be semiquinone
Describe the overall structure of complex 1 and where parts of it may have derived from
Structure looks like a boot. The shin part containing the FMN may have evolved from primitive dehydrogenase. The bottom pumping part may have derived from Na+/H+ pumps.
Describe the overall structure of complex 2 and where parts of it may have derived from
The top of it is the Succinate dehydrogenase containing the FAD.
Describe the role of Complex 3
Complex 3 receives 1 electron donated Ubiquinol oxidising to Semiquinone. As this happens, 2H+ are deposited in the intermembrane space. This electron is given to one cytochome c. The semiquinone is held in Complex 3 that interacts with haeme/iron complexes in complex 3. The semiquinone is further oxidised, and its electron is taken by another cytochrome c in a cyclic reaction. This causes 2 H+ from matrix to be dragged to the intermembrane space .
How many protons transferred by Complex 3 and where do they come from. How many electrons have been transferred per ubiquinone tho
2 from reduced QH2 and 2 from the matrix so 4 transferred in total. Only 2 electrons from the original ubiquinone though
What is cytochrome c
A protein electron carrier with a haeme in it. It only carries one electron. Found on the outer surface of the intermembrane space of all aerobic organisms.
What happens at complex 4 (Cytochrome c oxidase)
As 2 Cytochromes come in, O2 comes in and its pulled apart to separate O atoms. The Cytochrome cs are oxidised and its electron are used to pull 2 H+ to O to make H2O.
How does complex 4 pump protons, and how many pumped per electrons
The shape of the protein faces the matrix when it is oxidised and then when it has electrons transferred to it, it causes a conformational change that makes it face the Ims and deposit some H+, which pushes H+ through. It pumps 2 H+ per 2 electrons flowing through.
