Kreb's Cycle (TCA): Why H2O Needed in Isomerisation Step?

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In summary, the Krebs cycle involves an isomerisation step where fumaric acid is converted to malic acid by fumarase. While textbooks mention the addition of H2O in this step, the reason for this is not always clear. This is because malic and fumaric acid are stereoisomers, meaning they have the same chemical formula but differ in their spatial arrangement. Additionally, there is a confusion between maleic and malic acid, which are two different compounds with similar names. Maleic and fumaric acid are isomers, while malic acid has 2H and 1O extra. It is important to understand the differences between these compounds in order to fully grasp the TCA cycle.
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Suraj M
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In the isomerisation step of Krebs cycle, the second last step in regeneration. there is a change form fumaric acid to Malic acid by Fumarase. My textbook says that H2O is also added. From chemistry I know that that Malic and Fumaric acid are sterioisomers, Then why need that H2O??
 
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  • #2
You are confusing malic and and maleic?
 
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Oh I did not know they were two different compounds! So Maleic acid and fumaric acid are isomers and Malic acid has 2H and 1O extra! Got it thanks!
 
  • #4
Suraj M said:
Oh I did not know they were two different compounds! So Maleic acid and fumaric acid are isomers and Malic acid has 2H and 1O extra! Got it thanks!

The formulae should be spelt out in whatever text you are using. I think it is rather unsatisfactory that all these 'trivial names' for the various carboxylic acids are suddenly just thrown at students coming to the TCA cycle as if they were known, whereas they will never have met them before. Semi-systematic names - e.g. if they were all like alpha-keto-glutarate - would be better IMO.

As I see you are a frequent poster at this site, I will hopefully come back in the next few days with some other considerations about the TCA cycle you might find useful.
 
  • #5
Thank you epenguin :smile:
 

FAQ: Kreb's Cycle (TCA): Why H2O Needed in Isomerisation Step?

What is Kreb's Cycle (TCA)?

Kreb's Cycle (also known as the citric acid cycle or TCA cycle) is a series of biochemical reactions that occur in the mitochondria of cells. It is a crucial part of cellular respiration, which is the process by which cells produce energy.

Why is the Kreb's Cycle important?

The Kreb's Cycle is important because it is the primary source of ATP (energy) production in cells. It also plays a role in the production of important molecules such as amino acids and fatty acids, which are essential for various cellular processes.

How does the Kreb's Cycle work?

The Kreb's Cycle begins with the breakdown of glucose (sugar) into pyruvate. The pyruvate then enters the mitochondria and undergoes a series of reactions, which ultimately result in the production of ATP. Along the way, several intermediate molecules are produced, which are used to produce other important molecules.

Why is H2O needed in the isomerisation step of the Kreb's Cycle?

During the isomerisation step of the Kreb's Cycle, the molecule citrate is converted into isocitrate. This reaction requires the addition of a water molecule to proceed, making H2O an essential component of this step. The water molecule is later removed in a subsequent step, completing the isomerisation process.

What happens if there is not enough H2O in the isomerisation step of the Kreb's Cycle?

If there is not enough H2O in the isomerisation step, the reaction will not be able to proceed, and the cycle will be disrupted. This can lead to a decrease in ATP production and a buildup of certain intermediate molecules, which can have negative effects on the cell's metabolism and overall function.

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