oxidative phosphorylation Flashcards
How does the cell get NADH into the mitochrondrial matrix in order to be converted into ATP?
- Malate-Aspartate shuttle;
NADH in cytoplasm transfers protons to oxaloacetate to produce malate. A specific malate transporter transports Malate from the cytoplasm into the matrix. In the matrix, malate is then converted back into oxaloacetate so NAD+ is reduced back into NADH.
Oxaloacetate is then converted to Aspartate (using transaminase). Aspartate is then transported out the matrix.
DIAGRAM IN ON
Production of 3 ATP per NADH using this method
This system only works when the tissues are metabolically quiet (e.g liver)
- Glycerol-phosphate shuttle
Used when tissues are metabolically active.
Dihydroxyacetone phosphate is converted into glycerol-3-phosphate (in this process, it converts NADH into NAD+)
Mitochondrial version of glycerol 3- phosphate dehydrogenase converted the G-3-P back into DHA-P. In the process, FAD is converted to FADH2 from the protons released at G-3-P
Ultimately, these protons are transferred onto ubiquinone to make ubiquinol.
2 ATP’s per NADH oxidised
Where is FADH2 made in the mitochondria?
On the inner membrane when the succinate > fumarate happens
Order of oxidation of NADH through the complexes
1 > 3 > 4
Oxidation of NADH (NADH Q reductase) - complex 1
Oxidises NADH (to NAD+ AND H+) and transfers 2 electrons to mobile carrier un
Transfers 4 H+ from matrix to inner mitochondrial membrane
Ubiquinone > ubiquinol
THEREFORE 1 e- results in movement of 2H+ into the IMS
They then go onto complex 3
Oxidation of NADH - Complex 3
Receives 2 electrons from QH2 (ubiquinol) and transfers them to Cytochrome-C in IM space.
In this process, it can move 4 protons across from matrix to IM space.
They then go onto Complex 4
Oxidation of NADH - complex 4
Also called cytochrome oxidase
Transfers 2 electrons from 2 Cytochrome-c proteins to the mitochondrial matrix
In this process, 4H+ are transfered to the matrix (2 of these interact with oxygen to form water)
Oxidation of 1 NADH results in the transfer of approx. ___ H+. __ from complex 1, __ from complex 3, __ from complex 4
approx. 10 H+
4 from Complex 1
4 from complex 3
2 from complex 4
Oxidation of FADH2
Uses complex 2, 3, and 4
Also known as succinate dehydrogenase
Complex 2 in the conversion of succinate to fumarate (fad is reduced to FADH2)
FADH2 to FAD only produces 2 ATP
(4H+ from Complex 3, 2H+ from complex 4)
Why is complex 1 not used for the oxidation of FADH2?
Because fewer protons are transferred to the inner membrane
How is the electrochemical gradient produced by the electron transport pumps used to generate ATP?
Through the ATP synthase pump.
1) Driven by the movement of protons from IM space to Matrix, F0 rotor ring rotates
2) F0 Rotor ring (can move) rotates the central stalk (is stiff)
3) rotation drives formation of ATP
Roughly 3H+ are required per ATP.
Head group is made up of 3a and 3b subunits, they do move but don’t rotate. The b’s bind and make ATP.
What are the 3 different states of the beta subunits of the headgroup on the atp synthase pump? What are their functions?
L = Loose state, binds ADP + Pi
T = Tight state, binds ATP
O = Open state, binds ADP or ATP loosely (allows dissociation).
Process of the rotation stuff to make ATP (in ON)
- ADP + pi have access to binding site on O. then rotates.
- Loose binding on L then rotates
- Goes to tight binding, forcing ADP + Pi close together. Next rotation results in formation of ATP
- Rotation again, converts tight binding site to open conformation that’ll release the ATP. unbinding requires energy
How many ATP’s per 1 NADH?
3
How does ATP get out of the matrix to get into cytoplasmic space?
Specific transporter (ATP-ADP translocase)
ATP can only leave matrix if it’s replaced by an ADP and vice versa
How many ATP’s per FADH2
2
