The location that should have lowest oxygen concentration would be the tissue because it is the furthermost location.
Other location with lowest oxygen concentration should be in the right part of the heart. It is when all unoxygenated blood pooled before going to the lungs. But the left part of the heart will have highest oxygenated blood, so it's ambiguous.
High oxygen concentration should be found in the environment, lungs, and the blood.
The answer to this question would be hydrolysis
There is amylase enzyme inside saliva that will break down starch into maltose sugar. Maltose is the sugar that <span>causing </span>the sweet sensation in the tongue. Since it will take for the reaction to happen, the sweet taste only appears after a few moments after you chewing the bread.
The reaction that was catalyzed by amylase is hydrolysis.