Terminal oxidation flashcards

Question 1

What is terminal oxidation?

Answer 1

Electron transport + oxidative phosphorylation. Takes place in the inner mitochondrial membrane.

Question 2

Electron transport

Answer 2

Electron carriers transfer electrons and protons from reduced coenzymes (NADH and FADH) to oxygen— series of steps that oxidize reduced cofactors

Question 3

Oxidative phosphorylation

Answer 3

Reducing power from electron transport is converted into ATP energy

Question 4

Sources of NADH and FADH

Answer 4

NADH: Glycolysis (only source in cytosol), PDH, TCA cycle, beta-oxidation FADH: TCA cycle, beta-oxidation

Question 5

Reduction potential (E0)

Answer 5

More negative values mean strong reducing agents (tendency to lose electrons). Positive values are oxidizing agents (tendency to gain electrons). In ETC reactions start with components who lose electrons most readily and end with components with greatest affinity for electrons.

Question 6

Final acceptor of electrons in ETC?

Answer 6

Oxygen–this is also the most + E0 value in the series

Question 7

3 components of the electron transport chain

Answer 7

1. 4 large multi-subunit enzyme complexes (Complex I-IV) 2. Coenzyme Q 3. Cytochrome C

Question 8

What do Complexes I-IV contain?

Answer 8

Redox enzymes, coenzymes, metal ions which participate in the redox reaction

Question 9

Where does FADH join the ETC?

Answer 9

At the Coenzyme Q (Complex II) step. Side note: FADH is produced by Complex II but any other FADH that enters the ETC from other sources will enter at Coenzyme Q (won’t go to Complex II)

Question 10

Where does NADH join the ETC?

Answer 10

At the FMN (Complex I) step

Question 11

Coenzyme Q

Answer 11

Free-floating organic molecule which accepts electrons (is reduced) through FADH in Complex II and transfers electrons to Complex III (gets re-oxidized)

Question 12

Cytochrome C

Answer 12

Free-floating heme containing molecule with iron in Complex III

Question 13

Complex I

Answer 13

Transfers electrons and protons to Coenzyme Q

Question 14

Complex II

Answer 14

Succinate dehydrogenase (from TCA) produces FADH and transfers electrons and protons to Coenzyme Q. Located on the inside of the inner membrane.

Question 15

Complex III

Answer 15

Transfers electrons to Cytochrome C. Iron fluctuating between ferrous and ferric form and Cytochromes I and II present.

Question 16

Complex IV

Answer 16

Transfers electrons to molecular oxygen and makes H2O. Iron and copper are present.

Question 17

2 free-floaters in ETC

Answer 17

1. Coenzyme Q 2. Cytochrome C

Question 18

Rotenone in ETC

Answer 18

Fish poison which inhibits Complex I

Question 19

Amytal in ETC

Answer 19

Barbituate which inhibits Complex I

Question 20

1. Antimycin A 2. Myxothiazol 3. Stigmatellin in ETC

Answer 20

1 & 2: Antibiotics and 3: Chemical which all inhibit complex III

Question 21

Cyanide, sodium azide, carbon monoxide in ETC

Answer 21

Inhibit Complex IV (will stop everything upstream)

Question 22

Cyanide poisoning

Answer 22

Binds to ferric iron in the heme of Cytochrome C in Complex IV that is supposed to catalyze the cytochrome oxidase step. Mitochondrial respiration and energy production stop, rapid cell death. Treatment includes using nitrates which convert oxyhemoglobin to methemoglobin by oxidizing Fe2+ of hemoglobin (bad but lesser of two evils). Methemoglobin competes with Fe3+ for cyanide binding. Also thiosulfate reacts with cyanide to make nontoxic product.

Question 23

Iron atom in Cytochromes

Answer 23

Structure differs from Hemoglobin because the proximal His is switched with a Methionine which allows the iron to go through regular oxidation and reduction

Question 24

Protons in ETC

Answer 24

Protons pumped out from matrix to intramembrane space in Complex I, III, and IV and builds up a proton gradient

Question 25

Why does NADH produce 3 ATP and FADH only 2 ATP in ETC?

Answer 25

NADH enters cycle earlier at Complex I whereas FADH enters at Coenzyme Q

Question 26

Oligomycin

Answer 26

Stops ATP synthesis which stops electron transport

Question 27

F0F1ATPase

Answer 27

NOT an enzyme. Multi-protein complex which synthesizes ATP from ADP and Pi by using proton gradient. Ogliomycin-sensitive (will stop its’ functioning)

Question 28

F0F1ATPase structure

Answer 28

F1 (head) binds ADP and Pi and synthesizes ATP. Bottom portion of complex has the proton channel where protons flow from intermembrane space back to the mitosol. Connected by noncovalent interactions and changes conformation as a unit.

Question 29

Mechanism of F0F1ATPase

Answer 29

Proton flow–>Conformational change–>Transfer of electrochemical to mechanical energy–>ADP + Pi = ATP

Question 30

3 conformations of F0F1ATPase

Answer 30

L: Loose (binds ADP+Pi) T: Tense (forms ATP) O:Open (Releases ATP)

Question 31

Physiological uncoupling protein (UCP-1)

Answer 31

Thermogenesis (produce heat). Exception where the electron transport system is NOT linked to ATP production. Fatty acids in mitochondria are diverted to UCP-1 instead of entering TCA. Utilized by babies and hibernating animals effectively.

Question 32

Leber’s Hereditary Optic Neuropathy (LHON)

Answer 32

Point mutation in mitochondrial genes (in the circular DNA) for 3 subunits of Complex I–>Lowered activity of Complex I. Sudden onset of blindness, if more serious mental retardation, impaired speech, movement disorders.

Question 33

Mitochondrial myopathies

Answer 33

Affects Complexes I and IV. CNS affected, mitochondrial encephalomyopathy (ragged red fibers).

Question 34

Cytochrome B mutations

Answer 34

Lower activity of Complex III. Severe exercise intolerance, lactic acidosis. Can be treated with Vitamin C and Vitamin K which in combination can oxidize NADH and reduce Cytochrome C (bypassing CoQ and Complex III)