Electron Transport: Electron Flow from Coenzymes to Oxygen

Question 1

What is electron transport?

Answer 1

process of coenzyme reoxidation under aerobic conditions, involving stepwise transfer of electrons to oxygen by means of a series of electron carriers

Question 2

What is the electron transport system?

Answer 2

electron transfer is accomplished as a multistep process that involves and ordered series of reversibly oxidizable electron carriers function together

Question 3

How many kinds of electron carriers does the ETC consist of?

Answer 3

Five

Question 4

What are the five kinds of ETC carriers?

Answer 4

Flavoproteins

Iron-Sulfur Proteins

Cytochromes

Copper-Containing Cytochromes

Coenzyme Q

Question 5

Describe Flavoproteins.

Answer 5

transfer both electrons and protons

use either FAD or FMN as the prosthetic group

Question 6

Describe Iron-Sulfur Proteins.

Answer 6

family of proteins, each with an Fe-S center that consists of iron and sulfur atoms complexed with cysteine groups of the protein

electron carriers in the Fe

(only one electron and no protons)

Question 7

Describe Cytochromes.

Answer 7

contain iron but as part of porphyrin prosthetic group called HEME

5 types of cytochromes (b, c, c1, a and a3)

one electron carrier and no protons

only cytochrome c is a peripheral membrane protien that is loosely associated with the outer surface of the membrane

Question 8

Describe Copper-Containing Cytochromes.

Answer 8

cytochromes a and a3 contian a single copper atom bound to the heme group of the cytochrome

this forms a bimetallic iron-copper center

iron-copper center keeps O2 molecules bound to cytochrome oxidase complex until it has picked up four electrons and four protons, two water molecules are released

Question 9

Describe Coenzyme Q.

Answer 9

the only non-protein component of the ETS

also known as ubiquinone

freely mobile in the inner membrane, it serves as a collection point for electrons from reduced FMN and FAD-linked dehydrogenases

CoQ reduced in two successive steps ( 1e- & 1H+) to CoQH and then CoQH2

releases and accepts both protons and electrons

Question 10

Define standard reduction potential.

Answer 10

a measure in volts of the affinity a compound has for electrons

how easily a compound has for electrons and become reduced

Question 11

How are the electron carriers order based on their energy levels?

Answer 11

the position of each carrier is determined by its standard reduction potential

Question 12

What are respiratory complexes?

Answer 12

subset of carriers of the electron transport system consisting of a distinctive assembly of polypeptides and protsthetic groups, organized together to play a specific role in the electron transport process

Question 13

How many complexes are involved in the ETC?

Answer 13

4 complexes

Question 14

Describe what occurs in complex 1.

Answer 14

transfer electrons from NADH to CoQ - NADH-coenzyme Q oxidoreductase

Question 15

Describe what occurs in complex 2.

Answer 15

transfers to CoQ the electrons derived from succinate (TCA-6)

succinate-coenzyme Q oxidoreductase complex

Question 16

Describe what occurs in complex 3.

Answer 16

coenzyme Q-cytochrome c oxidoreductase complex

accepts electrons from CoQ and passes them to cytochrome c

Question 17

Describe what occurs in complex 4.

Answer 17

transfer electrons from cytochrome c to oxygen and is called cytochrome c oxidase

Question 18

How many protons are yielded from the 4 complexes?

Answer 18

10 protons