Now I'm at high school. And yesterday, I've learned that respiration is c6 o6 h12 broken by o2 to give co2 + h20 + energy. If the main content of glucose is carbohydrate(coh) then can we react water and c02 to get coh in any form? If we could get that, then we could just make an artificial canal from lungs to stomach. Please think about it and give me some explanative reply because i am only just trying to enter the world of biology.

Now I'm at high school. And yesterday, I've learned that respiration is c6 o6 h12 broken by o2 to give co2 + h20 + energy. If the main content of glucose is carbohydrate(coh) then can we react water and c02 to get coh in any form? If we could get that, then we could just make an artificial canal from lungs to stomach. Please think about it and give me some explanative reply because i am only just trying to enter the world of biology.

 

 

So you're basically saying that instead of breathing out carbon-di-oxide out of our lungs we can use it to produce carbohydrate compounds. Nature indeed has found this alternative strategy in few autotrophic bacteria living in extreme conditions which use reverse tricarboxylic acid cycle to produce carbohydrate compounds using CO₂ and H₂O.

To answer the question, CO2 fixation is not possible for us (bacteria and plants are able to do so, however). However I would also highlight (and probably confuse) the definition of respiration. What the OP provided is typical highschool introduction of respiration and, unfortunately, not quite accurate.

 

In the strictest sense respiration refers to the act of energy generation, but it is somewhat independent from e.g. sugar metabolism (e.g. catabolism of glucose). The actual process of energy generation via respiration is based on two elements. First, electron transfer from NAPDH to an electron acceptor (for eukaryotes it is oxygen, anaerobic prokaryotes are able to use other sources, including fumarate, nitrate, ferric iron etc.).

During this transfer protons are pumped out of the cell, resulting in a gradient that powers the ATP synthetase which actually phosphorylates ADP to ATP. Both processes together are generally referred to as cellular respiration. As you can see, there is no mentioning of sugars.

The reason is that the main producers of NADPH (i.e. the reduction equivalents) is the TCA cycle, which can be fueled by the catabolism of a large number of different C and N sources. Thus, the process of generating NADPH is actually fairly decoupled from the actual respiration (and it is slightly annoying that many highschool textbooks take glucose and treat it as gospel). Also note that the respiration occurs in mitochondria all over our bodies and not only in specialized organs. I.e. each of our cells has to respire, we just breathe to deliver oxygen to all the tissues (i.e. breathing is not actual part of the biochemical process, it is just a way to deliver the electron acceptors via blood to all our tissues and cells).

 

Finally, if you are interested in how CO2 fixation works, read up on the Calvin cycle.

Oxidative phosphorylation is indeed taught in the 12th grade. I'm not sure in which grade R A J A is in.