Module 3: oxidative phosphorylation

Question 1

Under aerobic conditions, what process is the primary source of ATP in the cell?

Answer 1

Oxidative phosphorylation

Question 2

where does oxidative phosphorylation occur?

Answer 2

inner mitochondrial membrane

Question 3

How do eletrons enter the electron transport chain?

Answer 3

Electrons enter via electron carriers NADH and FAHD2.
1. NADH enter ETC at complex 1, electrons move down chain releasing energy. (NADH –> NAD+)
2. FADH2 enters at complex 2, electrons move down chain releasing energy. (FADH2 –> FADH)

Question 4

How is the proton gradient formed?

Answer 4

As complexes undergo redox reactions, free energy released is used by complex 1,3, & 4 to pump a proton from the matrix to the intermembrane space. this generates a pH and electrochemical gradient (proton-motive force)

Question 5

What is oxidative phosphorylation?

Answer 5

production of ATP from ADP and Pi driven by free energy produced by electron transport in ETC
- flow of electrons doesn’t directly result in ATP synthesis

Pi= inorganic phosphate

Question 6

What is chemiosmotic hypothesis?

Answer 6

Protons transferred to intermembrane space re-enter the mitochondrial matrix through a channel in ATP synthase, driving ATP synthesis.

Question 7

What is the structure of ATP synthase?

Answer 7

6 domained protein embedded in inner mitochondrial membrane. contains a ring of peptides formed in membrane and a catalytic domain in matrix.
- has 3 active sites:
1. trapping ADP and Pi
2. ATP synthesis
3. ATP release and ADP and Pi binding

Question 8

What is the function of ATP synthase?

describe how it works

Answer 8

• The active sites move between 3 conformations, driven by proton motive force
• Gamma subunit turns “points” at subunit undergoing catalysis
• proton enters from intermembrane space binds to Glu in subunit c making it neutral
• rotates clockwise 9 steps before releasing into matrix
• ADP + Pi –> ATP