What is the Difference Between Digestion and Metabolism

The main difference between digestion and metabolism is that digestion is a type of catabolism event responsible for the breaking down of large molecules into small molecules whereas metabolism comprises of both catabolism and anabolism, breaking down large molecules and making large molecules from the small molecules. Furthermore, digestion involves both mechanical and biochemical processes while metabolism only involves in biochemical processes.

Digestion and metabolism are two processes that occur in animals bodies to produce energy and to maintain other cellular processes.

Key Areas Covered

1. What is Digestion
     – Definition, Process, Importance
2. What is Metabolism
     – Definition, Process, Importance
3. What are the Similarities Between Digestion and Metabolism
     – Outline of Common features
4. What is the Difference Between Digestion and Metabolism
     – Comparison of Key Differences

Key Terms

Anabolism, Catabolism, Chemical Digestion, Digestion, Enzymes, Mechanical Digestion, Metabolism

What is Digestion

Digestion is one of the four processes responsible for obtaining nutrients by higher animals. The other three are the ingestion, absorption of nutrients, and the elimination of waste. Here, the absorption of nutrients follows the digestion of food. Generally, digestion occurs in the alimentary canal of higher animals. But, in single-celled animals, it occurs inside vacuoles in the cytoplasm. The main importance of digestion is the breaking down of large food particles into small molecules, which can be readily absorbed by the digestive tract. Furthermore, digestion occurs by means of both mechanical and chemical digestion.

Mechanical Digestion

Mechanical digestion is responsible for the breaking down of large food particles into small particles, facilitating the chemical digestion. Moreover, the three events of mechanical digestion are chewing in the mouth, churning in the stomach, and segmentation in the small intestine. Chewing occurs by the action of teeth in the mouth while churning is the squeezing and mixing up of food with the gastric juice by the action of the muscles of the stomach. Furthermore, segmentation is the process responsible for the propulsion and the mechanical digestion of food through the small intestine.

Figure 1: Digestion

Chemical Digestion

Moreover, chemical digestion is responsible for the breaking down of high molecular weight molecules into small molecules. Also, the digestive enzymes secreted by various glands along the digestive tract drive this process. Furthermore, acids and bile facilitate the enzymatic action. During chemical digestion, carbohydrates, proteins, lipids, and nucleic acids are broken down into their monomeric forms. Therefore, chemical digestion can be considered as a catabolic process.

What is Metabolism

Metabolism is the collection of all biochemical reactions that occur inside the body of living organisms. It occurs through three main phases.  The first phase is the catabolism in which carbohydrates, proteins, fats, and nucleic acids in food are broken down into their small monomer units and nitrogenous wastes are eliminated. The second phase is the production of energy by using the resultant monomers such as glucose. Moreover, the third phase is the anabolism in which small monomer units polymerize to form complex molecules such as polypeptides, lipids polysaccharides, and nucleic acids. Ultimately, all of these biochemical reactions are responsible for the organism’s growth, development, maintenance of structures, reproduction and response to the outside environment.

Figure 2: Carbohydrate Metabolism

Furthermore, enzymes play a key role in metabolism by driving all biochemical reactions. Therefore, in order to keep the enzymes active, living organisms always maintain a constant internal environment in the body.

Similarities Between Digestion and Metabolism

• Digestion and metabolism are two processes that occur in the animal body.
• Biochemical processes occur in both processes. Therefore, enzymes take part in each process.
• Also, both processes are linked with catabolism.

Difference Between Digestion and Metabolism

Definition

Digestion refers to the process in the alimentary canal by which food is broken up physically, as by the action of the teeth, and chemically, as by the action of enzymes, and converted into a substance suitable for absorption and assimilation into the body. Metabolism refers to the sum of the physical and chemical processes in an organism by which its material substance is produced, maintained, and destroyed, and by which energy is made available. Thus, this explains the main difference between digestion and metabolism.

Type of Processes

Both mechanical and biochemical processes occur during digestion while only biochemical processes occur in metabolism.

Chemical Process

Moreover, only catabolism occurs in the digestion while both catabolism and anabolism occur in metabolism. Hence, this is another difference between digestion and metabolism.

Occurrence

Furthermore, digestion only occurs in animals while metabolism occurs in all living organisms including animals and plants.

Occurrence in Higher Animals

Besides, another important difference between digestion and metabolism is that while digestion occurs in the digestive system, metabolism occurs inside the cell.

Conclusion

Digestion is the process of breaking down food into small nutrients, which can be absorbed by the body. It occurs in the digestive tract in the higher animals. In lower animals, it occurs in the cytoplasm. Moreover, the two main events take place in digestion are mechanical and chemical digestion. Hence, it is a catabolic process. On the other hand, metabolism is the collection of biochemical reactions that occur inside the cell. Hence, it includes both anabolic and catabolic reactions. Metabolism occurs in all types of living organisms. Therefore, the main difference between digestion and metabolism is the type of process.

References:

1. “Principles of Digestion and Metabolism.” Stephen F. Austin State University, Available Here.

Image Courtesy:

1. “2405 Digestive Process” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia   
2. “2509 Carbohydrate Metabolism” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia   

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