BGM1002/L23 Oxidative Phosphorylation Flashcards
Why is oxygen required for oxidative phosphorylation?
To release energy from electron carriers NADH and FADH2
How many NADH and FADH2 are generated from each citric acid cycle?
3 NADH
1 FADH2
What is generated from NADH, FADH2 and O2 during oxidative phosphorylation?
Water
In which direction are protons pumped in oxidative phosphorylation?
Through membrane into matrix
What 2 ionisation states does iron switch between in molecules?
Fe2+ and Fe3+
What common feature exists between each step in oxidative phosphorylation?
Energy is released
What is electron motive force?
Pumping of protons from the mitochondrial matrix into the cytosol
What is proton motive force?
Movement of protons from the cytosol into the mitochondrial matrix down a concentration gradient, generating ATP
What occurs in step 1 of oxidative phosphorylation? (4)
Transfer of 2 high-potential electrons from NADH to FMN
Electrons from FMNH2 are transferred to Fe-S clusters
Electrons from Fe-S shuttled to coenzyme Q
2 chemical H+ removed from matrix
What complex is involved in step 1 of oxidative phosphorylation?
Complex 1
NADH-Q oxidoreductase
What is the overall proton transfer in step 1 of oxidative phosphorylation?
+4H+ in space
-6H+ in matrix
What enzyme is involved in step 2 of oxidative phosphorylation?
Complex II
Coenzyme Q
What is coenzyme Q also known as?
Ubiquinone
What occurs during step 2 of oxidative phosphorylation? (2)
Q carries electrons from NADH and FADH2
Coenzyme diffuses rapidly within inner mitochondrial membrane
What is the overall charge transfer in step 2 of oxidative phosphorylation?
+2e- in membrane
-6H+ in matrix
What enzyme is involved in step 3 of oxidative phosphorylation?
Complex III
Q-cytochrome c oxidoreductase
What occurs during step 3 of oxidative phosphorylation? (1)
Electrons transferred from QH2 to oxidised cytochrome c (Q-cycle)
What is the overall charge transfer during step 3 of oxidative phosphorylation?
2H+ removed from matrix
4H+ released to intermembrane space
What protein is involved in step 4 of oxidative phosphorylation?
Cytochrome c
Describe the structure of cytochrome c.
Small soluble protein
Contains c-type haem
Describe the function of cytochrome c.
Carries 1 electron from Q-cytochrome c oxidoreductase to cytochrome c oxidase
What is the overall charge transfer in step 4 of oxidative phosphorylation?
+8H+ in space
+4e- in membrane
-12H+ in membrane
What enzyme is involved in step 5 of oxidative phosphorylation?
Cytochrome c oxidase
What occurs during step 5 of oxidative phosphorylation? (3)
4e- from cytochrome c are transferred to O2
4H+ from matrix complete reduction of O2 to H2O
4 more H+ pumped across membrane to intermembrane space
What is the overall charge transfer in step 5 of oxidative phosphorylation?
+12H+ in space
-16H+ in matrix
Give 3 external factors that may affect oxidative phosphorylation.
Carbon monoxide
Cyanide
Salicylate
Mitochondrial defects
How is a proton pump initially driven?
Proton binding to an aspartate group
How does carbon monoxide affect oxidative phosphorylation?
High affinity for Hb reduces oxygen getting to cells
Binds to cytochrome-oxidase complex
How does cyanide affect oxidative phosphorylation?
Binds to Complex IV (cytochrome c oxidase) and blocks step 5
How does salicylate affect oxidative phosphorylation?
Forms pores in mitochondrial inner membrane
Protons pass through without generating ATP
