Question

Both Glucose and Fatty Acids can be completely oxidized to CO2, with the energy release used for the synthesis of ATP. In what ways are the biochemical processes involved similar or identical, and how do they diverge?

Answer 1

Both glucose and fattyacids can be completely oxidized to CO2. In short, glucose via glycolysis ends up forming pyruvate that ultimately get converted to acetyl coA. Now, this acetyl coA enters the TCA cycle which ultimately gives off 12 ATP and CO2.

Similarly, fatty acids get converted to fatty acyl coA and acetyl coA. This acetyl coA then enters the TCA cycle , thus getting oxidized to form CO2.

Thus we see that both the pathways enter the TCA cycle and get completely oxidized there.

Now, to get the details,

Fatty acids get converted to fatty acyl coA by the help of an enzyme thiokinase in the cytoplasm.

This then enters the mitochondria via MMCT ( mitochondrial membrane carnitine transporter).

Inside the michondria this fattyacyl coA undergo a 4 step reaction to ultimately form fattyacyl coA and acetyl coA.

This acetyl coA then enters the TCA cycle, while the fattyacyl coA is further utilised to enter the cycle thus it go on and on. This is known as the Beta oxidation of fatty acids.

net ATP produced is 12 in the tca cycle and 5 ATP in the beta oxidation process.

Similarly glucose enter the glycolysis pathway and get converted to pyruvate in the cytoplasm.

this then get converted to acetylcoA that enter mitochondria and join the TCA cycle.

this way both of these cycle end up having the same fate.