The key difference between metabolism and digestion is that metabolism is the complete set of biochemical reactions taking place in an organism while digestion is the breakdown of large insoluble food molecules into small molecules that can be absorbed into the bloodstream.
Both metabolism and digestion are important processes that occur in living organisms. As mentioned above, metabolism refers to the whole set of chemical and physiological reactions occurring in a living organism, including the animals and plants. Digestion, which is the breakdown of food, is also a part of metabolism.
CONTENTS
1. Overview and Key Difference
2. What is Metabolism
3. What is Digestion
4. Similarities Between Metabolism and Digestion
5. Side by Side Comparison – Metabolism vs Digestion in Tabular Form
6. Summary
What is Metabolism?
Metabolism is an extremely vital set of biochemical reactions taking place in order to sustain the life of organisms. Metabolic processes are essential to maintain the growth and development of the organisms, and the extraction of energy through metabolic pathways. Metabolism consists of two major processes known as catabolism and anabolism, which are responsible for harvesting and spending energy, respectively. Furthermore, catabolic processes such as digestion break down the organic matter into small molecules and cellular respiration produce and fulfils the energy requirement. Using the energy produced during catabolism, anabolic processes form vital components such as proteins and nucleic acids to sustain life in the organism.
Figure 01: Metabolism
The metabolic reactions are well organized as pathways due to the controlling of hormones and enzymes. Interestingly, metabolic pathways of all organisms are remarkably similar even in very distinctive species. Ecology and evolutionary biology provide explanations for these remarkable similarities. That means; the potential of metabolic activity determines the sustainability of life of a particular organism.
What is Digestion?
Digestion is the breaking down of food. Digestion usually contains a series of processes. There are two main types of digestion: mechanical digestion and chemical digestion. In digestion, simplification of large molecules into small monomers takes place. Hence, digestion is a catabolic process. In addition, there are mainly two forms of digestive systems based on the place of operation; primitive organisms have external digestion, while more evolved advanced animals have internal digestive systems.
Figure 02: Digestion
In advanced animals, digestion starts in the mouth and continues through the stomach and concludes at jejunum. While food passes through the oesophagus, the peristaltic movements help to breakdown it into smaller particles. Inside the stomach, the chemical digestion becomes predominant with the secretion of digestive enzymes and acids with optimum temperature. Protein digestion starts in the stomach and ends up in the small intestine after converting proteins into their monomers; amino acids. Lipid digestion starts and ends in the small intestine, which converts lipids into their monomers: glycerol and fatty acids. The mouth starts carbohydrate digestion, and it concludes in the small intestine after forming simple sugars. After all the digestive processes, the nutrients in food are ready for the absorption into the bloodstream.
What are the Similarities Between Metabolism and Digestion?
- Metabolism and digestion are important processes occurring in living organisms.
- Both processes include catabolic reactions.
- Chemical digestion or the enzymatic breakdown of food is a metabolic process. Therefore, chemical digestion falls under the realm of metabolism.
- Moreover, enzymes involve in both processes.
What is the Difference Between Metabolism and Digestion?
Both metabolism and digestion are reactions occurring in an organism. Digestion is a part of metabolism. Metabolism is the all chemical and physiological reactions occurring in a living organism that are necessary to maintain life. On the other hand, digestion is the breakdown of foods into small molecules that can be absorbed into the bloodstream. Therefore, this is the key difference between metabolism and digestion.
Moreover, digestion occurs only in the digestive system, but metabolism occurs in all systems in our body. Also, a further difference between metabolism and digestion is the type of reactions they involve. Metabolism includes both catabolic and anabolic reactions, but, digestion includes only catabolic reactions.
Furthermore, digestion occurs only in animals, while metabolism occurs in all living organisms. So, this is also a significant difference between metabolism and digestion.
Summary – Metabolism vs Digestion
Metabolism refers to the whole set of chemical and physiological reactions occurring in a living organism including the animals and plants. In contrast, digestion, a part of metabolism, refers to the chemical and mechanical reactions involving in the breakdown of ingested foods into small molecules in order to absorb into our body. Digestion is a type of catabolism. But, metabolism consists of both catabolism and anabolism. Furthermore, metabolism occurs in all the organ system in our body while digestion occurs only in the digestive system. Moreover, metabolism takes place in all living organisms while digestion takes place only in animals. Thus, this is a summary of the difference between metabolism and digestion.
Reference:
1. “Principles of Digestion and Metabolism.” Statewide Instructional Resources Development Center, Austin State University. Available here.
2. Newman, Tim. “Digestion: Anatomy, Physiology, and Chemistry.” Medical News Today, MediLexicon International, 11 Jan. 2018, Available here.
Image Courtesy:
1. “Human Metabolism – Pathways” By Evans Love – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “2426 Mechanical and Chemical DigestionN” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia