Details, Details…  


The TCA/Krebs/Citric Acid Cycle occurs in the mitochondrial matrix. It’s the final pathway whereby oxidative type of metabolism of amino acids, fatty acids and carbohydrates converge; i.e. their carbon skeletons are converted to carbon dioxide and water, also in turn generating a form of usable energy in the form of ATP (Adenosine-Triphosphate).


The Krebs cycle is the third of four metabolic pathways including: Glycolysis Pyruvate Processing and oxidative phosphorylation which are all interlinked.All of the individual steps that are involved in the TCA cycle amount to one great purpose. Basically, citric acid (citrate), a substance high in energy, is formed from oxaloacetate and acetyl CoA. Step-by-step, citrate loses little energy pockets, partly in the form of carbon dioxide and water also as GTP, NaOH and FADH2 (which provides electrons to complete the respiratory chain following the TCA cycle).

Finally, as a result of all these shenanigans, ATP (the mighty energy storing molecule) is produced and aids in most of the bio-chemical processes that occur within the body.In the TCA cycle, the remaining substances (not used for ATP production) are used to reconstruct the oxaloacetate molecule which would join to an acetyl CoA molecule thereby repeating the entire cycle once more (Encyclopedia Britannica 2013).

Enymes, Krebzymes?- A little regulation goes a long way…

Just in case you may have wondered if this little party ever stops, it doesn’t.

giphy (5)

…but it does slow down

In the cell, its need for ATP determines the rate of the Krebs cycle.

How, you might ask?

Both the Krebs cycle and its predecessor glycolysis, are continuously regulated by enzyme stimulation and inhibition. The cell, a responsible little factory, always prefers efficiency, and products never are manufactured in excess. This allows both glycolysis, and the Krebs cycle to work like a well-oiled machines. Once there’s more than enough ATP present to cater to the cell’s demanding energy needs, glucose is stored as fat or glycogen, ‘til the cell needs more.

Since we’re on the subject of more, activators do exactly the opposite.  Their function is regulatory, and they ensure that energy requirements are met. Activators, namely Ca2+ and ADP increase the manufacturing of products when the cell states that there’s not enough to go around. They essentially tell the enzymes, a-ketoglutarate dehydrogenase and isocitrate dehydrogenase, to increase the rate of production (Lodish 2008).



Encyclopedia Britannica. 2013. tricarboxylic acid cycle (biochemistry). [online] Available at: [Accessed: 16 Mar 2014].

FAMILY GUY ANIMATED GIF. n.d. [image online] Available at: [Accessed: 16 Mar 2014].

Lodish, H. F. 2008. Molecular cell biology. New York: W.H. Freeman and Co.

wait, The Krebs cycle occurs IN the matrix?!. n.d. [image online] Available at: [Accessed: 16 Mar 2014].

Contributors: Thalia, Roi


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