Catabolic Reaction

All living cells undergo catabolism, which is a metabolic reaction. Energy is released during catabolic reactions by breaking down large, organic molecules into smaller, simpler ones.

Anabolism, on the other hand, involves the synthesis of complex, organic molecules from smaller components.

Examples of Catabolic Reactions

The catabolic process breaks down large, complex molecules into smaller, simpler ones. As a result of hydrolysis, catabolic reactions release energy by breaking chemical bonds within larger molecules. 

An estimated 40% of the energy released is converted directly into adenosine triphosphate (ATP). Heat energy is released by catabolism and absorbed by body tissues and fluids as the remainder of energy.

Therefore, cells use catabolic processes to generate energy or fuel anabolic processes (which require energy).

Digestion and cellular respiration are examples of catabolic reactions.


Catabolism is exemplified by the digestion of food. Energy is released during digestion when large, complex food molecules are broken down into smaller components. Here are some examples:

  • Simple sugars are formed by the breakdown of complex carbohydrates
  • Amino acids are formed when proteins are broken down
  • Glycerol and fatty acids are formed when lipids are broken down

The organism uses the energy released by each of these reactions to grow and repair cells. It is possible to break down some of the smaller molecules released by digestion (for example, glucose) to release even more energy. New products are created through anabolic reactions.

Cellular Respiration

Throughout all living cells, cellular respiration plays an important catabolic role. The glucose in the cell is broken down to release energy, which is then used to power other reactions.

As far as cellular respiration is concerned, there are two types: aerobic respiration and anaerobic respiration. Neither aerobic respiration nor anaerobic respiration uses oxygen, but both are catabolic reactions.

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