MCP - Cross - 2/13 - Respiratory Chain and Ox Phos

Question 1

What important complexes of the respiratory chain are found in the mitochondrial membrane

Answer 1

I, III, IV

Question 2

Flavins, for example FMN (flavin mononucleotide) of NADH dehydrogenase exchange how many electrons?

Answer 2

Flavins are 2 electron donor/acceptors.

Question 3

Iron-sulfur (FeS) centers are 1 electron donor/acceptors, despite having 2-4 irons per center. From whom do FeS complexes accept electrons?

Answer 3

Flavins and Q

Question 4

Where are FeS electron donor/acceptors found?

Answer 4

Complex III, as an example

Question 5

What prominent amino acids surround the FeS centers?

Answer 5

2 cysteines, 2 histidines

Question 6

What 2 electron donor/acceptor acts as a cofactor and an electron buffer?

Answer 6

Ubiquinone

It is also very hydrophobic

Question 7

Hemes are 1 electron donor/acceptors such as cytochromes c and c1. What amino acids are the heme molecule attached to?

Answer 7

The heme attaches to 2 cysteine side chains.

Question 8

What amino acids does the iron atom in the center of c-heme coordinate with?

Answer 8

The Fe atom of the c-heme coordinates with a methionine and histidine side chain (in addition to 4 porphyrin-ring nitrogens)

Question 9

What 1 electron donor/acceptor characterizes complex IV?

Answer 9

Copper Center, for example CuB

Question 10

What centers in the respiratory chain are the only ones that will alloow O2 to bind due to their open coordination site?

Answer 10

The copper center of CuB and the heme iron of the Cyt a3 at the end of the respiratory chain.

Question 11

The F0F1 ATP synthase contains how many catalytic sites for ATP synthesis?

Answer 11

3

Question 12

Explain the concept of “Respiratory Control.”

Answer 12

1. The endergonic synthesis of ATP is obligatorily coupled to the exergonic redox reactions, but the reverse it also true. The redox reactions may not proceed without ATP synthesis.
2. An electrochemical gradient functions as a common intermediate linking oxidation to phosphorylation.
3. Oxygen consumption is coupled to ATP synthesis. The rate of respiration is controlled by the availability of ADP.
4. Back pressure from the electrochemical gradient stops the flow of electrons down the respiratory chain at those points where proton transport is coupled to a redox reaction, unless the protons are carried back into the matrix by the F0F1 ATP synthase.

Question 13

Name this reaction:

NADH + H+ + 1/2O2 + 3ADP + 3Pi –> NAD+ + 3 ATP + 4H2O

Answer 13

Oxidative phosphorylation

Question 14

The Q cycle, where Q accepts electrons from FeS dehydrogenase and cyt bh, and protons from the membrane, then diffuses to let go its its protons and electrons on the other side of the membrane, then cycles back, is known as an example of:

Answer 14

Mitchell’s Loops

Question 15

The F0F1 ATP synthase is a molecular motor driven by what?

Answer 15

Protons

Question 16

What are the roles of the transmembrane gradient of H+?

Answer 16

1. ATP synthesis
2. Transport of ADP and ATP
3. Heat
4. rotation of bacterial flagella
5. acidification of endomembrane compartments
6. transport of phosphate
7. antiports and symports of cations, sugars, aa’s

Question 17

What are the categories of oxidative phosphorylation inhibitors?

Answer 17

1. uncouplers (2,4-dinitrophenol) and ionophores (gramacidin, valinomycin)
2. phosphorylation inhibitors (oligomycin)
3. inhibitors of e transport (rotenone, amytal, antimycin A, CN-, CO)
4. inhibitors if mitochondrial transport systems (atractyloside, bongkrekic acid, mercurous salts)