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The Difference Between Digestion & Metabolism
31 May 10 - By S. Smith

The Difference Between Digestion & Metabolism

Digestion and metabolism are two body processes that are easily confused. I have done some research and prepared a simple explanation with website addresses for all data presented.



The Difference Between Digestion and Metabolism


Here are various definitions which make clear the difference. You will notice that certain key concepts are repeated in the definitions:

Digestion: "in the alimentary canal" "food is broken up" "food is converted" "breaking it down" "into substances suitable for absorption and assimilation" "making food absorbable"

alimentary canal  Encarta Dictionary

Digestive system: the tubular passage between the mouth and the anus, including the organs through which food passes for digestion and elimination as waste

Metabolism : "chemical processes" "within a living cell" "yield energy" "energy is made available" "energy is provided"

digestion Unabridged

1.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. has several dictionaries. Here's another one from the same page:

2. the organic process by which food is converted into substances that can be absorbed into the body

Merriam Webster Dictionary

: the action, process, or power of digesting: as a: the process of making food absorbable by dissolving it and breaking it down into simpler chemical compounds that occurs in the living body chiefly through the action of enzymes secreted into the alimentary canal

metabolism has several dictionaries
American Heritage

The chemical processes occurring within a living cell or organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized. has several dictionaries. Here's another one from the same page: Unabridged

1.Biology, Physiology. 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.

Compact Oxford English Dictionary

• noun the chemical processes in a living organism by which food is used for tissue growth or energy production.

Encarta Dictionary

1. life-sustaining chemical activity: the series of processes by which food is converted into the energy and products needed to sustain life

Merriam Webster dictionary

1 a: the sum of the processes in the buildup and destruction of protoplasm; specifically : the chemical changes in living cells by which energy is provided for vital processes and activities and new material is assimilated


I found this article explaining the relationship between metabolism and digestion. This article goes into more detail about the chemistry of cellular metabolism. It's fairly simple but may be more detail than you need so I have excerpted a simple explanation.

Metabolism -The Process of Digestion

"Digestion is a necessary first step for all foods. The molecules of which foods are made are too large to pass through the lining of the digestive system. Digestion results in the formation of smaller molecules that are able to pass through that lining and enter the person's bloodstream. (for example,) Sugar molecules formed by the digestion of starch enter the bloodstream. Then they are carried to individual cells throughout a person's body.

The smaller molecules into which nutrients are broken down make up the metabolic pool. The metabolic pool consists of the simpler substances formed by the breakdown of nutrients. ....

Cellular Metabolism

"Substances that make up the metabolic pool are transported to individual cells by the bloodstream. They pass through cell membranes and enter the cell interior. Once inside a cell, a compound undergoes further metabolism, usually in a series of chemical reactions. For example, a sugar molecule is broken down inside a cell into carbon dioxide and water, with the release of energy. ....

"The reverse of the process shown above also takes place inside cells. That is, energy ... can be used to put simpler molecules together to make more complex molecules. For example, suppose that a cell needs to repair a break in its cell wall. To do so, it will need to produce new protein molecules. Those protein molecules can be made from amino acids in the metabolic pool. ..."


I hope this helps people to understand these two separate but related processes better.

© 2010. S. Smith. All Rights Reserved