ETC And Ox Phos

Question 1

What is the main function of complex 1?

Answer 1

1. FMN coenzyme accepts 2 electrons from NADH and becomes FADH2, which are then transported to CoQ to make CoQH2.
2. It pumps 4 protons into the IMS.
3. An Fe-S bridge is used to facilitate the electron transfer in step 1.

Question 2

What is the function of complex 2?

Answer 2

1. 2 electrons are moved from either FADH2 to CoQ to form CoQH2.
2. No protons are pumped at this complex.
3. An Fe-S bridge is used to facilitate the electron transfer in step 1.

Question 3

What is the purpose of complex 3?

Answer 3

1. It contains a heme group that transfers between Fe2+ and Fe3+ to move electrons from CoQH2 to cytochrome c (oxidized) to form 2 cytochrome c’s (reduced), which is a mobile electron carrier in the IMS.
2. 4 protons are pumped into the IMS per CoQH2 used.

Question 4

What is the purpose of complex 4?

Answer 4

1. It contains 2 hemes (a and a3) and two copper ions to act as electron carriers to shift electrons.
2. (4 reduced cytochrome c’s)+(4 H+)+O2–>(4 oxidized cytochrome c’s)+2H2O.
3. Pumps 2H+ across into the IMS.

Question 5

What are the main blockers of the ETC complexes?

Answer 5

Rotenone: Blocks complex 1 electron transfer.
Antimycin A: Blocks CoQH2 electron transfer to cytochrome c in complex 3.
Cyanide/carbon monoxide: Blocks final electron transfer to oxygen at complex 4.
Everything before the block remains reduced, everything after the block remains oxidized. Leads to no ETC, thus no ATP synthesis.

Question 6

What is the overall reaction of the ETC?

Answer 6

NADH+11H(m)+0.5O2–>(NAD+)+10H(ims)+H2O

Question 7

Describe oxidative stress.

Answer 7

Occurs when more electrons enter the ETC than can be passed to O2, which leads to ROS formation.
Prevention occurs in matrix via O2- change to H2O2 via superoxide dismutase, which is then converted to water by glutathione peroxidase.

Question 8

What is P:O ratio, and the important ones?

Answer 8

Is the amount of ATP formed per pair of electrons that enters the ETC.
NADH ratio is 2.75.
FADH2 ratio is 1.64 due to skipping complex 1.

Question 9

What is respiratory control?

Answer 9

It is the coupling of ATP synthesis and electron transport so neither can occur without the other.
Note ADP addition greatly increases amount of oxygen consumption, signifying electron transport is increasing and more ATP is produced.

Question 10

Describe the highlights of one pair of electrons being moved down the ETC in terms of energy produced.

Answer 10

It leads to the production of 53 Cal, which is stored in the proton electrochemical gradient and proton motive force. 22 of these are used to generate 3 ATP, and the rest are used in ancillary reactions or dissipated as heat.

Question 11

Describe the function of ATP synthase in general.

Answer 11

Allows protons to flow through it, down their electrochemical gradient from the IMS into the matrix.

Question 12

Describe the mitochondrial ATP synthase.

Answer 12

FoF1
F1 is the ATPase domain with alpha and beta catalytic subunits, and a gamma stalk to connect it to Fo.
Fo is the proton pore commonly with 8 c subunits in its c-ring in mammals (up to 15 however). One full rotation of the c ring produces 3 ATP, and requires an equal number of protons to flow through it as their are c subunits in the ring.

Question 13

Describe eventual effect NADH has on the c ring.

Answer 13

1 NADH moves 10 protons into the IMS, 8 of which are used to flow back into the matrix through c8, causing a complete turn. The other 2 (plus a third from somewhere else) bring over the needed phosphates to create ATP. Thus 1 NADH makes 10/11 of 3 ATP, or 2.75 ATP.
1 FADH2 only pumps across 6 protons, thus makes 6/11 of 3 ATP, or 1.64 ATP.

Question 14

Describe result of uncoupler presence, and what is a common one?

Answer 14

2,4-dinitrophenol.
They carry protons across the inner membrane down their gradient, bypassing ATP synthase. Thus ATP synthesis stops, but electron transport and O2 consumption occur rapidly.

Question 15

What is the overall effect of one glucose?

Answer 15

Glycolysis: 2 ATP, 2 NADH
PDH: 2 NADH
TCA: 6 NADH, 2 FADH2, 2 ATP
The above NADH and FADH2 are used in oxidative phosphorylation to create 27.5 and 3.3 ATP, respectively, thus ~35 ATPs are made overall.

Question 16

What are the primary mitochondrial transporters, and how do they function?

Answer 16

1. Adenine nucleotide transported: Is electrogenic and responds to the created membrane potential. It is anti port and moves an ATP(4-) out of the matrix and an ADP(3-) into it.
2. Phosphate translocase: Functions due to the created pH gradient, and is symport. Moves H2PO4- and H+ into the matrix. This phosphate is used to make ATP.
   Note both of these are physically associated with the ATP synthase, and are called the ATPsynthesome.
3. Transhydrogenase: NADH+(NADP+)+H(ims)–>(NAD+)+(NADPH)+H(m). This also utilizes the proton gradient. This NADPH is needed in conversion of H2O2 to water.
   Each of the above three are the ancillary reactions.

Question 17

What are the effects of respiration inhibitors, phosphorylation inhibitors, and uncouplers on respiration, phosphorylation, and ancillary reactions?

Answer 17

Respiration inhibitors: CN- and CO. Block all three.
Phosphorylation inhibitors: Oligomycin. Ancillary reactions can continue as long as the gradient exists.
Uncouplers: DNP, UCP. Respiration remains only.