The advantage of the cell of gradual oxidation of glucose during compared with its combustion to CO2 and H20 in one single step is that?

Question

why is C correct and the others are wrong?

 

A.More free energy is released for a given amount of glucose oxidized

B.No energy is lost as heat

C.Energy can be extracted in usable amounts

D.More C02 is produced for a given amount of glucose oxidized

Answer 1

Lucas: Remember that in all chemical reactions, it doesn't matter how you get there if you start with the same thing and end with the same thing, the total amount of energy taken in or released is the same. So 'more energy' is out. Similarly, you'll always lose something as heat; that's the way the world works (or a law of thermodynamics, depending on how sophisticated you want to be). 

 

The question then becomes how much do you lose as HEAT and how much do you convert to others forms? If you lost it all as heat, then the primary goal of oxidative phosphorylation (conversion of electron energy of glucose into potential energy of ATP) fails.* The many steps of the electron transport chain followed by proton flow through ATPase 'harness' some of this electron energy so that instead of being lost as heat, it is captured in the sf form of a 3rd phosphate stuck onto ATP to form ATP.

 

The sum (energy lost as heat) + (energy stored in ATP) must equal the total free energy of glucose + O2 => CO2 + H2O. In general, your cells lose as little to heat as possible and capture as much into ATP as they can. Direct combustion releases ALL the free energy as heat, so zero ATP stored.

 

*Your body DOES sometimes 'choose' to 'waste' some of the potential of the proton gradient as heat; look up "brown fat" to learn more. In the 20s, diets were based on the same principle; check out 'DNP'. The diets worked, except that some folks heated themselves to death (literally), so the approach was deemed "not the best"

Answer 2

Gradual glucose oxidation releases ATP,  the energy currency of biological systems. Cells can only store small amount of ATP and therefore, gradual oxidation provides with energy supply for a relatively longer duration releasing only small amount of ATP at a time. That gets utilized for biological work and gradual glucose oxidation releases more ATP to replenish it.

 

Hope this is clear, if not then please post again.

 

Best,