Tutoring biology 12, you cover most of the human systems, including the digestive.  The tutor comments on a distinction that doesn’t come up in everyday life, but is relevant to biology 12.

People commonly know that digestion means the breaking down of food.  Depending on their training or interest, they may realize that the food is separated into useful molecules that are absorbed.  From there, the absorbed molecules are either consumed (for instance, in the case of glucose), or else they become part of the body (as with calcium).

Digestion itself is “broken down” into two types:  physical and chemical.  Physical digestion is the process of breaking bites of food into smaller and smaller pieces. It begins with chewing, then continues in the stomach, where the food is mashed into a soup.

Chemical digestion breaks down larger molecules (that the body can’t absorb) into smaller ones (that it can).  Mainly, it is done by enzymes, each of which reacts with a specific type of food molecule.  For instance, lipase breaks down fat molecules. Enzymes often end in -ase.

While physical digestion obviously starts in the mouth, chemical digestion does as well. Saliva contains salivary amylase, which begins decomposing starch into sugars.

Much more will be said about digestion in upcoming posts:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.