Lecture 35

Question 1

How can one describe the free energy change that occurs in the ETC when electrons are transported from NADH to oxygen?

Answer 1

1) deltaG = -nFdeltaE
2) deltaE = standard redox potential of the electron acceptor - standard redox potential of the electron donating pair
3) E for NAD+/NADH = -0.32V
E for 1/2 O2/H2O = +0.82V
deltaE = 0.82V - (-0.32V) = 1.14V
4) deltaG = -2 x 23,062 x 1.14 = -52,581 calories
5) Since the deltaG for hydrolysis of ATP is about 7300 calories, ideally multiple molecules of ATP can be synthesized from the oxidation of NADH

Question 2

What is another name for Coenzyme Q?

Answer 2

Ubiquinone

Question 3

How many complexes function in the electron transport chain (ETC)?

Answer 3

4

Question 4

What occurs in complex 1 of the ETC?

Answer 4

1) NAD+ is reduced to NADH + H+ by the oxidation of a substrate
2) NADH + H+ are oxidized by the reduction of FMN to FMNH2
3) FMNH2 is oxidized to FMN, causing CoQ to be reduced to CoQH2

Question 5

What occurs in complex 2 of the ETC?

Answer 5

1) Succinate is oxidized to Fumarate causing FAD to be reduced to FADH2
2) FADH2 is oxidized to FAD, causing CoQ to be reduced to CoQH2

Question 6

What occurs in complex 3 of the ETC?

Answer 6

1) CoQH2 is oxidized to CoQ causing Fe3+ to be reduced to Fe2+ in cytochrome b
2) Fe2+ in cytochrome b is then oxidized to Fe3+ causing Fe3+ in cytochrome c to be reduced to Fe2+

Question 7

What occurs in complex 4 of the ETC?

Answer 7

1) Fe2+ in cytochrome c is oxidized to Fe3+ causing Fe3+ in cytochromes a + a3 to be reduced to Fe2+
2) Fe2+ in cytochromes a + a3 is oxidized to Fe3+ causing 1/2O2 to be reduced to H2O

Question 8

What is another name for complex 1 in the ETC?

Answer 8

NADH-CoQ reductase complex

Question 9

What is another name for complex 2 in the ETC?

Answer 9

Succinate-CoQ reductase complex

Question 10

What is another name for complex 3 in the ETC?

Answer 10

CoQH2-Cytochrome c reductase complex

Question 11

What is another name for complex 4 in the ETC?

Answer 11

Cytochrome c oxidase complex

Question 12

What complexes form the proton gradient found in the ETC and where are the protons shuttled from?

Answer 12

Complexes 1, 3, and 4 transport protons from the mitochondrial matrix to the intermembrane space of the mitochondria in order to produce a proton gradient

Question 13

How can ATP be produced following the ETC?

Answer 13

If, and only if, the protons produced from the ETC proton gradient travel back to the mitochondrial matrix through complex 5 (an ATP synthase), ATP will be produced from ADP + Pi in the mitochondrial matrix

Question 14

Where does ATP go once it is produced by ATP synthase?

Answer 14

It needs to be shuttled back towards the cytosol for use and therefore goes through an ATP transporter to go from the mitochondrial matrix to the intermembrane space (exchanges ATP for ADP; this is called an antiporter)

Question 15

What inhibits oxidative phosphorylation at complex 1?

Answer 15

Rotenone

Question 16

What inhibits oxidative phosphorylation at complex 3?

Answer 16

Antimycin A

Question 17

What inhibits oxidative phosphorylation at complex 4?

Answer 17

1) Carbon monoxide

2) Cyanide - very fast acting decrease of ATP + death

Question 18

What inhibits oxidative phosphorylation at complex 5?

Answer 18

Oligomycin

Question 19

What inhibits oxidative phosphorylation at ATP/ADP Translocase (Antiporter)?

Answer 19

Atractyloside

Question 20

What is the most notable use of Rotenone and Antimycin A?

Answer 20

They are used most commonly for killing fish because they are absorbed through the gills easily

Question 21

What are uncoupling proteins?

Answer 21

1) Uncoupling proteins can be naturally occurring or synthetic molecules that create a “proton leak,” allowing protons to reenter the mitochondrial matrix without capturing any energy as ATP
2) Electron transport chain is not inhibited
3) Energy is released as heat (can be used for warmth)
4) Examples are 2,4-dinitrophenol and uncoupling protein 1 (thermogenin), a protein in the mitochondria of brown adipose tissue

Question 22

What are variables that affect the yield of ATP from the complete oxidation of glucose?

Answer 22

1) Aerobic or anaerobic conditions
2) Electron shuttle (glycerol phosphate shuttle or malate aspartate shuttle)
3) Reduced coenzyme (NADH, 2.5 - 3 ATP or FADH2, 1.5 - 2 ATP)

Question 23

How many molecules of ATP are produced from oxidative phosphorylation?

Answer 23

1) The complete oxidation of glucose to carbon dioxide directly yields 2 ATP, 2 GTP, 10 NADH, and 2 FADH2
2) Depending on the assumptions used with respect to the electron shuttle and ATP yield, this could be the equivalent of 30 to 38 ATP molecules per molecule of glucose oxidized to CO2
3) Much greater than 2 molecules of ATP obtained from anaerobic glycolysis of glucose

Question 24

What are diseases associated with defects in cellular respiration and oxidative phosphorylation?

Answer 24

1) Hereditary defects in cell respiration and oxidative phosphorylation are very rare
2) These defects tend to result in lactic acidosis and muscle and nerve pathology
3) Examples: Lebers hereditary optic neuropathy & Leigh syndrome