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Electron transport chain

Where do the electrons come from?

The electron transport chain , or ETC , is made up of a group of protein complexes that undergo a series of red/ox reactions to translocate protons across the membrane to generate a PMF. Electrons enter the ETS from a high energy electron donor, often times this is in the form of NADH or FADH 2 , which are generated during catabolism (oxidation of carbon compounds, such as sugars or proteins or fats). Use the electron tower below (figure 1) as a reference guide to orient you as to where each component sits. Depending on the complexity of the ETC being used, electrons can enter at a variety of places depending upon the energy level of those entering electrons. To enter the ETC (electrons being donated to a red/ox complex within the chain), the electron donor must have a lower electronegativity than the electron acceptor (the complex that is taking the electrons). The donor will become oxidized and the acceptor will become reduced. The difference in the reduction potential between the donor and acceptor is the measure of energy released. If sufficient energy is released the cell can use it to do work, and in the case of an ETC that work would include translocating a proton from one side of the membrane to the other, setting up a PMF.

Electron Tower

Note : electrons entering the ETC do not have to come from NADH or FADH 2 . Many other compounds can serve as electron donors, the only requirement is that there exists an enzyme that can oxidize the electron donor and then reduce another compound. Even a small amount of energy can add up. For example there are bacteria that use H 2 as an electron donor. This is not too difficult to believe because the half reaction 2H + + 2 e - /H 2 has a reduction potential (E 0 ' ) of -0.42 eV. If these electrons are eventually donated to oxygen then the ΔE 0 ' of the reaction is 1.24 eV and that is equivalent to a lot of energy, a large negative ΔG (-ΔG). Alternatively, there are some bacteria that can oxidize iron, Fe 2+ at pH 7 to Fe 3+ with a reduction potential (E 0 ' ) of +0.2 eV. These bacteria use oxygen as their terminal electron acceptor and in this case, the ΔE 0 ' of the reaction is approximately 0.62. Not so great, but still produces a -ΔG. The bottom line is that depending on the electron donor and acceptor that the organism uses, a little or a lot of energy can be harvested and used by the cell per electrons donated to the electron transport chain.

What are the complexes of the etc?

ETCs are made up of a series (at least one) of membrane associated (some are integral) red/ox complexes that move electrons from a donor source, such as NADH, to a final acceptor, such as oxygen (that's what we use). Each requires a reduced substrate as an electron donor and an oxidized substrate as the electron acceptor. In most cases the electron acceptor is a member of the enzyme complex. Once the complex is reduced, the complex can serve as the substrate (source of electrons) for the next reaction. In other words, think of the ETC as a series of complexes that passes electrons to the next complex, which eventually uses some oxidized compound as the final substrate (referred to as the terminal electron acceptor ).

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
what does post-translational control refer to?
Teresa Reply
Bioremediation includes
Rachel Reply

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Source:  OpenStax, Ucd bis2a intro to biology v1.2. OpenStax CNX. Sep 22, 2015 Download for free at https://legacy.cnx.org/content/col11890/1.1
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