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Question: How many times does decarboxylation occur in the aerobic breakdown of one glucose molecule and when ...

How many times does decarboxylation occur in the aerobic breakdown of one glucose molecule and when does it occur?

Explanation

Solution

Hint : Decarboxylation is indeed a chemical reaction in which a carboxyl group is removed and carbon dioxide is released. Decarboxylation is usually described as a reaction between carboxylic acids that removes a carbon atom from a carbon chain. Carboxylation, or the addition of CO2C{O_2} to a compound, is the reverse process, and is the first chemical step in photosynthesis.

Complete Step By Step Answer:
During the aerobic breakdown of one glucose molecule, decarboxylation happens six times.
Each of the six carbon atoms in a glucose molecule must be converted into CO2C{O_2} .
The glucose molecule gets split into two three-carbon fragments during glycolysis (pyruvate).
In a preparatory step, these fragments are fed into the Tricarboxylic Acid Cycle.
Preparatory Step:
As pyruvate is converted into Acetyl−CoAAcetyl - CoA by pyruvate dehydrogenase, the first carbon atom of pyruvate is removed as CO2C{O_2} .
CH3COCOO−⏟pyruvate+NAD++H−SCoA→dehydrogenasepyruvateNADH+CO2+CH3CO−SCoA⏟Acetyl−CoA\underbrace {C{H_3}COCO{O^ - }}_{pyruvate} + NA{D^ + } + H - SCoA\xrightarrow[{dehydrogenase}]{{pyruvate}}NADH + C{O_2} + \underbrace {C{H_3}CO - SCoA}_{Acetyl - CoA}
Tricarboxylic Acid Cycle:
The Tricarboxylic Acid Cycle is shown in detail.

In Steps 33 and 44 of the Tricarboxylic Acid Cycle, the remaining two carbons are lost as CO2C{O_2}
Step 33 . Isocitrate to α−ketoglutarate\alpha - ketoglutarate
In this step, the second CO2C{O_2} molecule is formed.
O−COH(OH)C(COO−)CH2COO−⏟isocitrate+NAD+→dehydrogenaseisocitrateO−COCOCH(COO−)CH2COO−⏟oxaloacetate+NADH+H+\underbrace {\mathop O\limits^ - COH\left( {OH} \right)C\left( {CO{O^ - }} \right)C{H_2}CO{O^ - }}_{isocitrate} + NA{D^ + }\xrightarrow[{dehydrogenase}]{{isocitrate}}\underbrace {\mathop O\limits^ - COCOCH\left( {CO{O^ - }} \right)C{H_2}CO{O^ - }}_{oxaloacetate} + NADH + {H^ + }
O−COCOCH(COO−)CH2COO−⏟oxaloacetate+NADH+H+→dehydrogenaseisocitrateO−COCOCH2CH2COO−⏟α−ketoglutarate+CO2\underbrace {\mathop O\limits^ - COCOCH\left( {CO{O^ - }} \right)C{H_2}CO{O^ - }}_{oxaloacetate} + NADH + {H^ + }\xrightarrow[{dehydrogenase}]{{isocitrate}}\underbrace {\mathop O\limits^ - COCOC{H_2}C{H_2}CO{O^ - }}_{\alpha - ketoglutarate} + C{O_2}
Step 44 . α−ketoglutarate\alpha - ketoglutarate to succinyl−CoAsuccinyl - CoA
In this step, the third CO2C{O_2} molecule is formed.
\underbrace {\mathop O\limits^ - COCOC{H_2}C{H_2}CO{O^ - }}_{\alpha - ketoglutarate} + CoASH + NA{D^ + } \\\ \xrightarrow[{dehydrogenase}]{{\alpha - ketoglutarate}}\underbrace {CoA - S - COC{H_2}C{H_2}CO{O^ - }}_{succinyl - CoA} + C{O_2} + NADH \\\

Note :
The Tricarboxylic acid cycle (TCA cycle), also known as the Krebs cycle or the citric acid cycle, is the second stage of the three-stage mechanism by which living cells break down organic fuel molecules which is in the presence of oxygen to harvest the energy they need to expand and divide.