What are the results of the chemical digestion of carbohydrates, proteins and fats? Does this digestion occur in the mouth, stomach and/or the small intestine?
Glucose , amino acids, fatty acids and glycerol. All those are the monomers of those macromolecules.
Chemical digestion occurs wherever enzymes are involved.
And since we have amylase in our saliva in our mouths, chemical digestion of carbohydrates starts here.
In the esophagus, the digestion of carbohydrates continues as the bolus of food is held together by our saliva which contains amylase.
As the bolus of food enters the stomach, the digestion of carbohydrates stops as amylase gets denatured due to the low pH (2) due to hydrochloric acid (HCl). However, the digestion of proteins starts by the release and activation of pepsinogen to pepsin. Here, polypeptides are hydrolysed to dipeptides and if possible, amino acids (end-product of protein digestion).
As the chyme enters the small intestine, the pH is raised by the pancreatic juices and bile, as 8 is the optimum pH of enzymes here (duodenum). Protein digestion is continued by trypsin.
Now it's very important to note that the action of bile is not chemical digestion. It just emulsifies the fat (break it to small droplets), to increase its surface area for the action of lipase (released in pancreatic juices- chemical digestion). Here emulsified lipid is hydrolysed to fatty acids and glycerol by lipase.
It is also worth noting that there are other enzymes like maltase and sucrase, in the pancreatic juices that ensure complete hydrolysis of carbohydrates to glucose.