ETC

Question 1

List 2 functions of electron transport chain

Answer 1

• > To re-oxidize NADH back to NAD+, using oxygen as the final electron acceptor,
• > Oxidative phosphorylation to produce ATP

Question 2

What enters electron transport chain?

Answer 2

2 NADH from glycolysis
2 NADH (pyruvate -> acetyl-CoA, 2 rounds of oxidative phosphorylation)
6 NADH + FADH2 (2 x 1 krebs cycle)

Question 3

Equation for the oxidation of NADH

Answer 3

NADH -> NAD+ + H+ + 2e-

Question 4

Equation for the reduction of 2e-

Answer 4

2e- + H+ + 1/2 O2 -> H2O

Question 5

General idea of Electron transport chain

Answer 5

Energy is released when electrons from NADH and FADH2 go from a higher state to a lower state. The 2e- is carried through transition molecules, slowly releasing energy until it becomes 2e-, where it is then used to reduce oxygen to water.

Question 6

What enters electron transport chains?

Answer 6

Reduced coenzymes such as NADH and FADH2
2 NADH from glycolysis
2 NADH from oxidative decarboxylation of 2 pyruvate
6 NADH and 2 FADH2 from 2 Krebs cycle

Question 7

Location of electron transport chain

Answer 7

In the inner mitochondrial membrane.

Question 8

What happens in the electron transport chain

Answer 8

Electrons will be shuttling from 1 complex to another complex.
Complex 1, complex 2, complex 3, cytochrome C.

Throughout the carriers, H+ is pumped out from mitochondria into inter-membrane space. Hence the electron carriers are used to pump H+ across the inner mitochondrial membrane into the intermembrane space.

Question 9

Oxidative phosphorylation

Answer 9

Chemiosmosis coupled with ETC become ATP synthesis.

Phosphorylation of ADP to ATP via ATP synthase

Question 10

ATP synthase

Answer 10

A large protein complex with a protein channels that allow re-entry of protons.

Question 11

List the 7 electrons carriers

Answer 11

Complex 1 (NADH dehydrogenase, can pump 4 H+, directly receives NADH)
Complex 2 (directly receives FADH2, FADH2 do not bypass complex 1, hence FADH2 produce less ATP as it does not energize the proton pump in complex 1)
Complex 3 (cytochrome oxidoreductase, can pump 2H+)
Complex 4 (reduce oxygen, oxygen picks up nearby hydrogens to form water, can pump 4 H+)
ATP synthase
Coenzyme Q (connects complex 1 and 2 with 3)
Cytochrome C (connects complex 3 and 4)

Question 12

Cytochrome C

Answer 12

Cytochrome C transport the electrons from complex 3 to complex 4

Question 13

Why build up H+

Answer 13

The free energy from the electron transport chain are used to pump hydrogen ions into the intermembrane space from the matrix.

The excess of hydrogen ions in the intermembrane space creates a pH and electrochemical gradient

Question 14

Chemiosmosis

Answer 14

Chemiosmosis is the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient.

Question 15

NADH ATP yield according to Mr Tai

Answer 15

3 ATP

Question 16

FADH2 ATP yield according to Mr Tai

Answer 16

2 ATP

Question 17

ATP synthesis

Answer 17

ATP synthesis is driven by the resulting current of protons flowing from the intermembrane space back to the matrix through the ATP synthase complex, generating ATP from ADP +Pi.

Question 18

General summary

Answer 18

Protons (H+ ions) are translocated across the membrane, from the matrix to the inter-membrane space, as a result of the oxidation of NADH/FADH2 through the electron transport chain. The continued buildup of protons creates a proton gradient.

Electrons are transported across the membrane through a series of protein carriers.

Oxygen is the terminal electron acceptor, combining with electrons and water to form water.

Proton gradient created drives hydrogen back through the membrane, through ATP synthase, creating a proton motive force that synthesizes ATP from ADP + an inorganic phosphate group.