Difference Between Absorption and Assimilation

The key difference between absorption and assimilation is that absorption is the process of taking the digested simple molecules into bloodstream/lymph from the intestinal villi and microvilli while assimilation is the process of synthesizing new compounds from the absorbed molecules.

Humans are heterotrophs. Hence, they utilize carbonic foods synthesized by autotrophic organisms. Heterotrophic nutrition constitutes five sequential processes. They are ingestion, digestion, absorption, assimilation and ejection.  Here, the digestive system and its coordinating organs play a major role in accomplishing the above steps. Besides, there are certain variations and specific adaptations along the alimentary canal to facilitate the different steps of heterotrophic nutrition.

CONTENTS

1. Overview and Key Difference
2. What is Absorption
3. What is Assimilation
4. Similarities Between Absorption and Assimilation
5. Side by Side Comparison – Absorption vs Assimilation in Tabular Form
6. Summary

What is Absorption?

Absorption is the process of taking the digested simple molecules into the bloodstream/lymph via the intestinal villi and microvilli. Hence, absorption takes place in the small intestine. Ingested foods by mouth undergo both mechanical and chemical digestion. Likewise, this occurs at different locations in the digestive tract. Mechanical digestion mainly occurs in the buccal cavity due to the grinding of food by teeth and mixing of it by the tongue. Along with the mechanical digestion, chemical digestion also begins at the mouth. Here, carbohydrates get partially digested due to the action of ptyalin enzyme. Likewise, through the series of enzymatic reactions occurring in digestion, macromolecules break down into simple molecules in order to facilitate absorption.

Absorption takes place in the small intestine. It is designed to maximize its surface area by folding into villi and microvilli. And, this structure facilitates the absorption of simple molecules such as amino acids, fatty acids, monosaccharides, etc. Then, the absorbed molecules pass into the bloodstream or lymph via the blood vessels present beneath the villi and microvilli. Lymphatic system absorbs only fatty acids and cholesterol molecules which they later get back into the bloodstream. Absorption occurs via both active and passive transport.

What is Assimilation?

Assimilation is the process of synthesizing new compounds from the absorbed molecules from the small intestine. Once the molecules are absorbed into the bloodstream, they are transported and distributed to every cell in the body. Therefore, assimilation involves the conversion and integration of these molecules with the living tissues. It could also be termed as the development of macromolecules through simple absorbed molecules.

Moreover, assimilation mainly takes place in the liver. It synthesizes essential components such as enzymes hormones, nucleic acids, etc. Therefore, assimilation is an important process to maintain cellular activities at optimum conditions.

What are the Similarities Between Absorption and Assimilation?

• Both absorption and assimilation are steps of heterotrophic nutrition.
• In order to produce essential macromolecules, absorption should happen before assimilation.
• Also, both processes occur inside our body.

What is the Difference Between Absorption and Assimilation?

Absorption is the process of taking simple molecules, which are produced as a result of digestion into the body (bloodstream/lymph) from the intestinal cavity. On the other hand, assimilation is the process of making new compounds from the absorbed molecules, which are necessary for normal cell functioning or to produce energy. Thus, this is the key difference between absorption and assimilation. When considering the locations where they occur, absorption takes place mainly in the small intestine while assimilation takes place in the liver. Hence, this is another difference between absorption and assimilation.

Furthermore, during the absorption, nutrients are adding into the bloodstream but, during the assimilation, molecules are taken out of the bloodstream by different cells. Thus, it is also a difference between absorption and assimilation.

Summary – Absorption vs Assimilation

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.

Reference:

1. Study.com, Study.com. Available here 
2. Goenka, Shruti. “Heterotrophic Nutrition – What Is It And What Are Its Types?” STYLECRAZE, IncnutIncnut. Available here  

Image Courtesy:

1.”Absorption of proteins in small intestine”By Sonabi – Own work, (CC BY-SA 4.0) via Commons Wikimedia 
2.”Anatomy and physiology of animals From ingestion to egestion”By Sunshineconnelly (CC BY 3.0) via Commons Wikimedia