Lecture 31 Flashcards
What is the electron transport chain? How are the complexes arranged?
The electron transport chain is organised as a series of complexes, between which mobile carriers carry electrons. These complexes float around the inner membrane, if the right ones collide with each other thing will happen.
How do electrons move in the ETC, what occurs in the complex 1 start and what does the pathway end in?
The movement of electrons through the ETC involves carriers undergoing a series of redox reactions as they move between the complexes. In complex 1, NADH is oxidised to NAD+ via a series of carriers, this pumps out 4 protons for each NADH oxidised (from matrix to intermembrane space, not the same protons from NADH) and coenzyme Q recieves the electrons. Coenzyme Q then transports the electrons to complex III via the Q cycle to a series of carriers which will then donate the electrons to the peripheral membrane protein Cyt c which then moves to complex IV which then travels to oxygen. Eventually this pathway ends with oxygen becoming reduced to water.
What increases as the electrons move from carrier to carrier? What occurs to the energy?
As the electrons move through the carriers in the ETC some energy is released, the movement is through the reduction potential from lowest (NADH) to highest reduction potential (Oxygen).
What is different about the complex II start and complex I start for the ETC?
In complex II FADH2 is oxidised at complex II, releasing two electrons into the ETC, the electrons then go to co enzyme Q as in the complex I start. No protons are pumped at this one (the only one which doesn’t).
How many protons are pumped out by eaach complex? How much for each main carrier?
Complex III and I pump out 4 protons each, Complex IV pumps out 2. NADH leads to 10 protons pumped, FADH2 leads to 6 protons pumped.
How many electron redox reactions can coenzyme Q undergo? How many does it give to Complex III and what does this mean for cytochrome C?
Coenzyme Q undergoes two-electron redox reactions (both changing C=O groups to -OH), but these can be accepted/released one at a time to complex III, which will then release one electron at a time to cytochrome C).
How many eectrons does cytochrome C provide to complex IV and how does it work? How does complex IV work also?
Cytochrome C is a mainly alpha helix protein which contains a heme group (4Ns to 1 Fe), it carries the electrons via reversible Fe2+/Fe3+ states. It moves along the intermembrane space side of the inner mitochondrial membrane and delivers electrons to complex IV. It delivers one electron at a time and hence two are required to join two protons and one oxygen atom to produce one water (however the overall equation will be 4H+ the 4e- + O2 produces 2H2O). At the same time it also pumps out two protons.
What are examples of molecules which can stop our electron transport chain?
Cyanide can inhibit cyt a3 which is used in complex IV, thereby lowering the ability to reach the terminal electronxide acceptor state. Rotenone inhibits the transfer of e- from complex I to coenzyme Q. Carbon monoxide can bind to the irons of the cytochromes of complex IV.
