<P> Digestion is the breakdown of large insoluble food molecules into small water - soluble food molecules so that they can be absorbed into the watery blood plasma . In certain organisms , these smaller substances are absorbed through the small intestine into the blood stream . Digestion is a form of catabolism that is often divided into two processes based on how food is broken down : mechanical and chemical digestion . The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes . In chemical digestion , enzymes break down food into the small molecules the body can use . </P>
<P> Digestion is the breakdown of large insoluble food molecules into small water - soluble food molecules so that they can be absorbed into the watery blood plasma . In certain organisms , these smaller substances are absorbed through the small intestine into the blood stream . Digestion is a form of catabolism that is often divided into two processes based on how food is broken down : mechanical and chemical digestion . The term mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes . In chemical digestion , enzymes break down food into the small molecules the body can use . </P>
where are most substances absorbed into the blood
where are most substances absorbed into the blood
the small intestine
the small intestine