Chapter 10: Electron Transport Chain and Oxidative Phosphorylation Flashcards
Give some properties as to why O2 is good for energy generating capacity?
- Oxygen is found almost everywhere on the earth’s surface
- oxygen diffuses easily across cell membranes
- under certain circumstances oxygen is highly reactive so it can readily accept electrons. This capacity is also responsible for another property of oxygen, its tendency to form highly destructive metabolites called reactive oxygen species ( ROS).
What is the terminal electron acceptor extracted from fuel molecules?
O2
ETC is a series of what?
- electron carriers in the inner membrane of the mitochondria of eukaryotes and the plasma membrane of aerobic prokaryotes
ETC is a series of electron carriers arranged in the inner membrane in order of what?
- increasing electron affinity; it is these molecules that transfer the electrons derived from reduced coenzymes to oxygen.
During the transfer of electrons there is a ___ in reduction potential that occurs.
decreease
When NADH is the electron donor and oxygen is the electron acceptor the change in standard reduction potential is what?
+0.82V-(-0.32V)= +1.14V
The process in which oxygen is used to generate energy from food molecules is sometimes called what?
cellular respiration
The energy released during electron transfer is coupled with what?
several ednergonic processes….prominently ATP synthesis
What are the principle sources of electrons?
- reduced coenzymes from glycolysis, TCA and fatty acid oxidation
Where are the components located for ETC in eukaryotes? What are they organized into?
- inner mitochondrial membrane
- four complexes
L> consisting of several proteins and prosthetic groups.
Complex 1 is also called what?
NADH dehydrogenase complex
L> catalyzes the transfer electrons from NADH to UQ (ubiquinone)
Sources of NADH?
TCA……….fatty acid oxidation
Which complex is the largest?
Complex 1
L> made of 25 different polypeptides……
What is complex 1 made up of?
- FMN, seven iron sulfer centres
What are iron sulfur centres?
they mediate one electron transfer reactions…..proteins that contain these are called nonheme ion proteins.
Function of complex 1?
- NADH reduces FMN to FMNH2…electrons are transferred from FMNH2 to an iron sulfur centre….1 electron at a time…….after the transfer from one IS center to another the electrons are eventually donated to UQ…
What is UQ?
a lipid soluble mobile electron carrier capable of accepting/donating electrons one at a time.
Electron transport is accompanied by the net movement of what?
protons from the matrix across the inner membrane and into the inter membrane space.
What is the other name for Complex 2?
- succinate dehydrogenase complex
What is the succinate dehydrogenase complex composed of?
- TCA enzyme succinate dehydrogenase and two iron sulfur proteins.
Complex 2’s function?
- mediates the transfer of electrons from succinate to UQ. The oxidation site for succinate is located on the larger of the iron sulfur proteins…..it is covalently bound to FAD
In some cells what doe glycerol-3-phosphate dehydrogenase do?
- located on the outer face of the inner mitochondrial membrane transferring electrons from cytoplasmic NADH to the ETC.
Acetyl-CoA dehydrogenase ???
transfers electrons to UQ from the matrix side of the inner membrane.
* first enzyme in fatty acid oxidation
Complex 3 is also called??
cytochrome b
What is complex 3 composed of?
11 subunits
L> three cytochromes ( bL, bH and C1 ) and one iron sulfur centre
What are cytochromes?
- a series of electron transport proteins that contain a heme prosthetic group similar to those found in hemoglobin and myoglobin
L> electrons are transferred by cytochromes one at a time in association with a reversible change in the oxidation state of a heme ion.
(ex: btwn a reduced Fe 2+ and an oxidized Fe 3+)
Function of Complex 3?
transfer of electrons from reduced coenzyme Q (UQH2) go a protein called cytochrome C (cyt c)
Complex 3:
Cytochrome c?
is a mobile electron carrier that is loosely associated with the outer face of the inner mitochondrial membrane.
The passage of electrons through complex 3 is referred to what?
Q cycle
Complex 3:
What is the overall reaction for the process which each UQH2 donates two electrons to cytochrome C?
UQH2+ 2 cyt cox (Fe3+) + (2H+)—–> UQ + 2 cyt red (Fe2+) + 4H+ (cytosol)
Complex 3:
During the Q cycle coenzyme Q molecules diffuse within the inner membrane between the electron donors in?
complex 1 or 2 and the electron acceptor in complex 3 ( the iron sulfur protein).
Complex 3:
How many electrons does UGH2 donate?
two electrons one at a time
Complex 3:
One electron flows to the _____, which then transfers it to ___ which it is then donated to ___.
Fe-S protein
cyt c1
cyt c
Complex 3:
-The second electron flows to ___ and then to ___ which then transfers this electron to an oxidized ____ to generate ______.
cyt bL
cyt bH
CoQ molecule (UQ)
UQ semiquinone (UQ-)
Complex 3:
Where are the protons released to from the oxidation of UQH2?
inner membrane space.
Complex 3:
-The other electron from the second UQH2 ??
- its transferred to cyt bL and b H and then its donated to UQ semiquinone . As UQ- accepts this electron it also binds two protons from the matrix to form UQH2.
Complex 3:
give an overview for the products!
- two molecules of cyt c are reduced, four protons are released into the inner membrane space and a molecule of UQH2 is regenerated from UQ-
What is complex 4 called?
- cytochrome oxidase
complex four catalyzes?
- catalyzes the four electron reduction of O2 to form H2O
Complex 4:
- made up of??
- membrane spanning complex
- 6-13 subunits
- cytochrom a and a 3………and three copper ions.
- Two copper ions form CuA/CuA a binuclear Cu-Cu center and heme a3 and CuB from a binuclear Fe-Cu center.
L> both centres accept one electron at a time.