Question

1. The main difference in reactions between the TCA cycle and the glyoxylate cycle is that the glyoxylate cycle does not have any oxidative decarboxylation reactions.

True or False

Answer 1

Answer: True

Reason: By oxidative decarboxylation, the oxidation reactions take place that produces the carbon dioxide by the successful removal of some carbon atoms or groups. This is one of the important steps in the Citric acid cycle.

One of the main difference that lies between the Citric acid cycle and the Glyoxylate cycle is that the later i.e. the Glyoxylate cycle bypasses or go past the 2 decarboxylation steps of the Citric acid cycle those are:

Firstly, the conversion of acetate takes place into succinate via isocitrate lyase enzyme and the malate via malate synthase.

There are many plants and bacteria that maintain this on acetate or on some other compounds. As their metabolic pathway is different than others.

Whereas, in the Citric acid cycle, the CO2 is produced three times in contrast to the Glyoxylate cycle which bypasses these steps,

1. When pyruvate is converted to Acetyl CoA by the enzyme pyruvate dehydrogenase.

2. When isocitrate converts into α-Ketoglutarate by the enzyme Isocitrate dehydrogenase.

3. α-Ketoglutarate to Succinyl CoA by the enzyme α-Ketoglutarate dehydrogenase

Another important difference between the two pathways is that two molecules of acetyl CoA enter inside the glyoxylate cycle while one molecule of acetyl CoA enters in the citric acid cycle.