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It is the destiny of wine to be drunk, and it is the destiny of glucose to be oxidized. But it was not oxidized immediately: its drinker kept it in his liver for more than a week, well curled up and tranquil, as a reserve aliment for a sudden effort; an effort that he was forced to make the following Sunday, pursuing a bolting horse.
Primo Levi, The Periodic Table , 1975

If oxygen is available, aerobic cellular respiration will go forward. In eukaryotic cells, the pyruvate molecules produced at the end of glycolysis are transported into mitochondria, which are the sites of aerobic cellular respiration. There, pyruvate (three carbons) will be transformed into an acetyl group (two carbons) that will be attached to a carrier compound called coenzyme A (CoA). The resulting compound is called acetyl-CoA . CoA is made from vitamin B5, pantothenic acid. Acetyl-CoA can be used in a variety of ways by the cell, but its major function is to deliver the two-carbon energy source derived from pyruvate to the next stage of the aerobic cellular respiration pathway.

Oxidation of pyruvate

In order for pyruvate, the product of glycolysis, to enter the next pathway, it must undergo several changes. The conversion is a three-step process ( [link] ).

This illustration shows the three-step conversion of pyruvate into acetyl CoA. In step one, a carboxyl group is removed from pyruvate, releasing carbon dioxide. In step two, a redox reaction forms acetate and NADH. In step three, the acetate is transferred coenzyme A, forming acetyl CoA.
Upon entering the mitochondrial matrix, a multi-enzyme complex converts pyruvate into acetyl-CoA. In the process, carbon dioxide is released and one molecule of NADH is formed.

Step 1. A carboxyl group is removed from pyruvate, releasing a molecule of carbon dioxide into the surrounding medium. The result of this step is a two-carbon hydroxyethyl group bound to the enzyme (pyruvate dehydrogenase). This is the first of the six carbons from the original glucose molecule to be removed. This step proceeds twice for each glucose molecule (remember: there are two pyruvate molecules produced at the end of glycolsis). Thus, two of the six carbons will have been removed at the end of this step in aerobic cellular respiration.

Step 2. The hydroxyethyl group is oxidized to an acetyl group, and the electrons are picked up by NAD + , forming NADH. The high-energy electrons from NADH will be used later to generate ATP.

Step 3. The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl-CoA.

During the oxidation of pyruvate, the incoming pyruvate is converted to acetyl-CoA, NAD + is reduced to NADH and a carbon dioxide is released for each pyruvate entering the stage ( [link] ).

Overview of oxidation of pyruvate
This image is an overview of the oxidation of pyruvate. During this stage, carbon dioxide is release, NAD + is reduced to NADH and acetyl-CoA is formed. (Image by Eva Horne and Robert Bear)

Krebs cycle

In the presence of oxygen, the two carbons in acetyl-CoA are added to to a four-carbon molecule, oxaloacetate, to form citrate (aka citric acid), a six-carbon molecule. This is the starting point of the Krebs Cycle, which will harvest the remainder of the extractable energy from what began as a glucose molecule. This single pathway has several different names: the citric acid cycle (for citric acid, the first compound in the cycle), the tricarboxylic acid (TCA) cycle (since citric acid has 3 carboxyl groups, and is thus a tricarboxylic acids), and the Krebs cycle , after Hans Krebs, who first identified the steps in the pathway in the 1930s in pigeon flight muscles. This work earned Krebs a share (with Fritz Lippman) of the 1953 Nobel Prize in Physiology and Medicine.

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Principles of biology. OpenStax CNX. Aug 09, 2016 Download for free at http://legacy.cnx.org/content/col11569/1.25
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