Oxidative Phosphorylation

Question 1

Describe oxidative phosphorylation and the ETC.

Answer 1

• occurs in the inner mitochondrial membrane (impermeable to small ions (H, Na and K) and small molecules (ATP))
• final common pathway from which electrons derived from different fuels of the body flow to oxygen

Question 2

Describe the organization of oxidative phosphorylation and ETC.

Answer 2

• five different protein complexes (I-V)
• each complex accepts or donates electrons to relatively mobile electron carriers (coenzyme Q and cytochrome C)
• free energy is released as electrons are transferred along the ETC from an electron donor (reducing agent or reductant) to an electron acceptor (oxidizing agent or oxidant)
• electrons ultimately combine with oxygen to form water
• Complex V: catalyzes ATP synthesis (ATP synthase)

Question 3

Describe the action of Complex I.

Answer 3

• Complex I: NADH Dehydrogenase
• transfers the hydrogen atoms to Coenzyme Q

**Complex 1, 3 and 4 generate H+ ions, which can be used in the ATP Synthase to generate ATP
-Electron transport is coupled to the phosphorylation of ADP by the pumping of protons from the matrix to the intermembrane space

Question 4

What is Coenzyme Q?

Answer 4

-mobile carrier that can accept the hydrogen atoms (FMNH2) and from FADH2 produced on succinate dehydrogenase (Complex II) and other enzymes and transfer them to Complex III

Question 5

Describe Complex II

Answer 5

• Complex II: Succinate dehydrogenase
• converts succinate into fumarate making FADH2

Question 6

Describe Complex III

Answer 6

• Cytochrome bc1
• Transfers electons with Fe

**Complex 1, 3 and 4 generate H+ ions, which can be used in the ATP Synthase to generate ATP
-Electron transport is coupled to the phosphorylation of ADP by the pumping of protons from the matrix to the intermembrane space

Question 7

Describe Complex IV

Answer 7

• Cytochrome a + a3
• Transfers e- using Fe

**Complex 1, 3 and 4 generate H+ ions, which can be used in the ATP Synthase to generate ATP
-Electron transport is coupled to the phosphorylation of ADP by the pumping of protons from the matrix to the intermembrane space

Question 8

Describe what happens when ETC is blocked.

Answer 8

• electron transport is tightly regulated so if you inhibit one process than it inhibits another
• uncoupling proteins create a proton leak that allows protons to reenter the mitochondrial matrix without capturing any energy as ATP

Question 9

What does Complex V do?

Answer 9

• Complex V: catalyzes ATP synthesis (ATP synthase)