Difference between absorption and assimilation

• Absorption is taking simple molecules, which were produced as a result of digestion into the body (blood stream/lymph) from the intestinal cavity. Assimilation is making new compounds from the absorbed molecules, which are necessary for normal cell functioning or to produce energy.
• Absorption is mainly taking place at the small intestine. Assimilation is taking place in the liver or any other cell.
• In absorption, nutrients are added to the blood stream or lymph, but in assimilation, nutrients are taken out from the blood stream/ lymph.
 

Both absorption and assimilation are steps of heterotrophic nutrition. The key difference between absorption and assimilation is that absorption is the process of taking digested simple molecules into bloodstream/lymph via the intestinal villi and microvilli while assimilation is the process of synthesizing new compounds from the absorbed molecules. Furthermore, absorption takes place via active and passive transport and occurs mainly in the small intestine. On the other hand, assimilation mainly takes place in the liver. Moreover, it helps cell growth and development as well as new cell production. This is the summary of the difference between absorption and assimilation.