Etc

Question 1

What is the name of the first complex in the ETC??

Answer 1

Complex 1
NADH Dehydrogenase or NADH Q Reductase

Question 2

Name of the second complex?

Answer 2

Complex II
Succinate Dehydrogenase or Succinate Q Reductase

Question 3

Name of the third complex??

Answer 3

Cytochrome Reductase or Cytochrome C oxidoreductase

Question 4

Name of complex IV ??

Answer 4

Complex IV
Cytochrome C oxidase

Question 5

What are the two mobile electron carriers in ETC?

Answer 5

Q or CoQ or Coenzyme Q or Ubiquinone and
Cytochrome C

Question 6

Ubiquinone ??

Answer 6

Ubiquinone (also called coenzyme Q, or simply Q) is a lipid-soluble benzoquinone with a long isoprenoid side chain.
Ubiquinone can accept one electron to become the semiquinone radical (•QH) or two electrons to form ubiquinol (QH2) and, like flavoprotein carriers, it can act at the junction between a two- electron donor and a one-electron acceptor.
Because ubiquinone is both small and hydrophobic, it is freely diffusible within the lipid bilayer of the inner mitochondrial membrane.
And because it carries both electrons and protons, it plays a central role in coupling electron flow to proton movement.

Question 7

Cytochrome ?!?!

Answer 7

The cytochromes are proteins with characteristic strong absorption of visible light, due to their iron-containing heme prosthetic groups.
Mitochondria contain three classes of cytochromes, designated a, b, and c, which are distinguished by differences in their light-absorption spectra.
Each type of cytochrome in its reduced (Fe2+) state has three absorption bands in the visible range.

Question 8

Fe-S proteins !?

Answer 8

In iron-sulfur proteins, the iron is present not in heme but in association with inorganic sulfur atoms or with the sulfur atoms of Cys residues in the protein, or both.

All iron-sulfur proteins participate in one-electron transfers in which one iron atom of the Fe-S cluster is oxidized or reduced.

Question 9

Endergonic reaction

Answer 9

DelG>0

Question 10

Exergonic rxn

Answer 10

DelG<0

Question 11

The transfer of two electrons from NADH through the respiratory chain to molecular oxygen can be written as?

Answer 11

NADH + H+ + 1/2O2 —> NAD+ + H2O

Question 12

For each pair of electrons transferred to O2, four protons are pumped out by Complex I, four by Complex III, and two by Complex IV. The vectorial equation for the process is therefore

Answer 12

NADH + 11Hn+ + 1/2 O2 —> NAD+ + 10Hp+ + H2O

Question 13

What are the two components of the proton motive force ?

Answer 13

(1) the chemical potential energy due to the difference in concentration of a chemical species (H ) in the two regions
separated by the membrane, and
(2) the electrical potential energy that results from the separation of charge when a proton moves across the membrane
without a counterion

Question 14

What happens in complex 1 ?

Answer 14

• The electrons of NADH enter complex I. It contains 2 types of prosthetic groups. FMN (which exists as a flavoprotein) and Fe-S cluster (which exist as Fe-S proteins,
the iron ion of which alternate between Fe+2 and Fe+3 states).
• Thereducingequivalents(2electronsandH+)fromNADHarefirstacceptedby
FMN to form FMNH2•
• The electrons from FMNH2 are then transferred to Fe-S clusters.
• The electrons are finally transferred to mobile carrier Q (CoQ or Coenzyme Q).

Question 15

What happens in complex 2 !?

Answer 15

• Complex II is a part ofTCA cycle enzyme, succinate dehydrogenase, where FADH2 is formed with the oxidation of succinate to fumarate.
• The electrons from FADH2 are transferred to Fe-S centers and then to Q.

Question 16

What happens in complex 3 !?

Answer 16

• Complex III has Cytochrome b and cytochrome c1 and Fe-S clusters.
• Cytochromes are conjugated proteins with heme as prosthetic group. The iron ion of cytochromes alternate between Fe+2 & Fe+3 states during electron transport.
• CoQ transports a single electron to Cyt b of complex III. The electron from CoQ is first recieved by Cyt b, which then transfers it to FeS. From FeS electrons are transferred to cyt c1. Electrons from cyt c1 are then transferred to mobile carrier cytochrome C.

Question 17

What happens in complex 4 ?!

Answer 17

• Cytochrome oxidase contain cytochrome a, cytochrome a3 and copper ions.
• The electrons from Cyt c is first recieved by Cyt a, which then transfers it to copper.
From copper electrons are transferred to cyt ~-
• cyt a3 (of Cytochrome oxidase) then finally delivers the electrons to oxygen, which forms water. Oxygen is the final acceptor of electrons.