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How to memorize the Krebs Cycle (Citric Acid Cycle)

Many college student go crazy when they are first presented with the task of memorizing the Krebs/ Citric Acid cycle. So many steps and enzymes and carbon dioxides flowing around. Guess what. There is a very easy way to remember it, AND retain it for years to come without ever looking back in the book.

[gn_note color=”#00aa00″]Check out the Krebs Cycle “Drag n Drop Game” for more practice Here![/gn_note]

….and we have 2 molecules of acetyl CoA to start with. If you don’t understand that please see the post about glycolysis.

I will go over how i memorized the names of all the molecules in the Krebs cycle, then the enzymes between each step, and then finally…if you are up to it how to draw each molecule. The easiest way to get this dreadful cycle in your head is by using mnemonics. This will take practice and its best that you don’t try to study this for the 1st time the day before the test.

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The Mnemonic Technique

To remember the molecules of the citric acid (Krebs) cycle i remeber this phrase as a hint to what molecules come first in the Citric Acid Cycle:










You should not just look at this and try to remember it. You should look at this, say it out loud, and write it down several times by memory. This helps people learn in a visual, auditory, and hands on manner. Once you are very familiar with these terms you should almost be able to recite them without the mnemonics.

*note: Citrate= Citric Acid, Fumarate= Fumaric Acid, etc…

Cictric Acid Cycle molecules
Molecules of the Citric Acid Cycle


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Citric Acid Cycle + Enzymes

For MOST of the enzymes, the name of the enzyme consist of the molecules it modifies(the molecule directly before it, and the function the molecule carries out):

So———-citrate Synthetase



Dance———-isocitrate Dehydrogenase

Devon———-alpha-ketoglutarate Dehydrogenase

Sipped———-Succinyl-CoA Synthetase

Down———-Succinate Dehydrogenase


Drinks———-malate Dehydrogenase

Cictric Acid Cycle enzymes
Cictric Acid Cycle enzymes


The key to remembering how many CO2 or NAD H is made you just need to remember that 3 out of the 4 dehydrogenase enzymes will remove 2 H atoms(and an electron)  from the molecule an put it onto a NAD, and remove a carbondioxide(CO2) molecules. That NAD will become NADH2. The only exception to this rule is the enzyme that produces Fumarate; Succinate Dehydrogenase. It actually places 2 H atoms on an FAD molecule instead of an NAD molecules. See pic above


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Citric Acid Cycle Molecular Level

I have finally found time to to create the image showing the citric acid cycle at the molecular level. The picture is self explanatory with comments where I thought they were necessary. Feel free to post suggestions or feedback. I would really appreciate it!

The Citric Acid Cycle at the Molecular Level:

Citric Acid Cycle Molecular Level


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What is next?

After completing glycolysis and the Krebs Cycle (Citric Acid Cycle) inside of your cells there is still a net production of only 4 ATP. In order to produce more ATP the molecules of NADH and FADH2 travel from the matrix of the mitochondria to the inner membrane. If you think you are ready for the electron transport stage of cellular respiration then click here.

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Other Related Processes

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Benefits of Fiber

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[/gn_column] [gn_divider top=”1″] [gn_spoiler title=”Literature referenced in this article:” open=”0″ style=”1″]

Brooker,Windmier,Graham, and Peter Stiling. Biology. McGraw-Hill   Science Engineering Math, 2007. Print.
Mauseth, James. Botany: an introduction to plant biology. 4th. Jones & Bartlett Learning, 2009. Print.

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  1. Yea!! This how I began to love molecular cycles and eventually signal-transduction pathways. I have some of those pathways that have not been linked to this article yet.


    Glycogen Metabolism

  2. Hey.. That was very helpful.. There is one mistake in ezyme part… When Oxaloacetate is converted to Citrate, enzyme CITRATE SYNTHASE helps nd not CITRATE SYNTHETASE… 🙂

  3. Hiii, this was really helpful.. Structures especially. Its a whole lotta work. Thanks n God bless..

  4. Love it
    Love it
    Love it
    It’s A Big Deal

  5. This is how I remember TCA:
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