Difference Between Anabolism and Catabolism

Key difference - anabolism vs. catabolism

Anabolism and catabolism are the sets of metabolic processes collectively referred to as metabolism. Anabolism is the series of reactions involved in the synthesis of complex molecules starting from the small molecules in the body. Catabolism is the series of reactions that are involved in breaking down complex molecules such as proteins, glycogen and triglycerides into simple molecules or monomers such as amino acids, glucose or fatty acids. The main difference between anabolism and catabolism is that anabolism is a constructive process and catabolism is a destructive process .

This article explains

1. What is anabolism - definition, processes, stages, function 2. What is catabolism - definition, processes, stages, function 3. What is the difference between anabolism and catabolism?

Difference Between Anabolism and Catabolism - Comparative Summary

What is anabolism?

The series of reactions that start from small molecules to synthesize complex molecules is called anabolism. So anabolism is a constructive process. Anabolic reactions require energy in the form of ATP . They are considered endergonic processes. The synthesis of complex molecules builds up tissues and organs step by step. These complex molecules are required for the growth, development and differentiation of cells. They increase muscle mass and mineralize the bones. Many hormones such as insulin, growth hormone, and steroids are involved in the process of anabolism.

There are three phases involved in anabolism. In the first stage, precursors such as monosaccharides, nucleotides, amino acids and isoprenoids are produced. Second, these precursors are activated into an active form using ATP. Third, these reactive forms are assembled into complex molecules such as polysaccharides, nucleic acids, polypeptides, and lipids.

Organisms can be divided into two groups based on their ability to synthesize complex molecules from simple precursors. Some organisms, such as plants, can synthesize complex molecules in the cell from a single carbon precursor such as carbon dioxide. They are known as autotrophs. Heterotrophs use intermediate complex molecules such as monosaccharides and amino acids to synthesize polysaccharides or polypeptides. On the other hand, organisms can be divided into two groups, phototrophs and chemotrophs, depending on the energy source. Phototrophs get energy from sunlight, while chemotropes get energy from the oxidation of inorganic compounds.

Carbon fixation from carbon dioxide is achieved either through photosynthesis or chemosynthesis. In plants, photosynthesis takes place through the light reaction and the Calvin cycle. Photosynthesis produces glycerate-3-phosphate, which hydrolyzes ATP. Glycerate-3-phosphate is later converted into glucose by gluconeogenesis. The enzyme glycosyltransferase polymerizes the monosaccharides to produce monosaccharides and glycans. An overview of photosynthesis is shown in Figure 1 .

Difference Between Anabolism and Catabolism

Figure 1: Photosynthesis

During the fatty acid synthesis, acetyl-CoA is polymerized to fatty acids. Isoprenoids and terpenes are large lipids that are synthesized from the polymerization of isoprene units during the mevalonate pathway. During amino acid synthesis, some organisms are able to synthesize essential amino acids. Amino acids are polymerized to polypeptides during protein synthesis. De novo and salvage pathways are involved in the synthesis of nucleotides, which can then be polymerized into polynucleotides during DNA synthesis.

What is catabolism?

The series of reactions that break complex molecules down into small units is known as catabolism. So catabolism is a destructive process. Catabolic reactions release energy in the form of ATP as well as heat. They are considered exergonic processes. The small molecule units that arise in catabolism can either be used as precursors in other anabolic reactions or can release energy through oxidation. Hence, it is believed that catabolic reactions generate chemical energy that is required by the anabolic reactions. Some cellular wastes such as urea, ammonia, lactic acid, acetic acid, and carbon dioxide are also produced during catabolism. Many hormones such as glucagon, adrenaline and cortisol are involved in catabolism.

Depending on the use of organic compounds as a carbon source or electron donor, organisms are classified as heterotrophs or organotrophs. Heterotrophs break down monosaccharides like intermediate complex organic molecules in order to generate the energy for cellular processes. Organotrophs break down organic molecules to create electrons that can be used in their electron transport chain and generate ATP energy.

Macromolecules such as starch, fats and proteins from food are absorbed by digestive enzymes during digestion and broken down into small units such as monosaccharides, fatty acids or amino acids. Monosaccharides are then used in glycolysis to make acetyl-CoA. This acetyl-CoA is used in the citric acid cycle. ATP is produced through oxidative phosphorylation. Fatty acids are used to make acetyl-CoA through beta-oxidation. Amino acids are either reused in protein synthesis or oxidized to urea in the urea cycle. The process of cellular respiration with glycolysis, citric acid cycle and oxidative phosphorylation is shown in Figure 2.

Key difference - anabolism vs. catabolism

Figure 2: Cell respiration

Difference Between Anabolism and Catabolism


Anabolism: Anabolism is the metabolic process in which simple substances are synthesized into complex molecules.

Catabolism: Catabolism is the metabolic process in which large molecules are broken down into smaller molecules.

Role in metabolism

Anabolism: Anabolism is the building phase of the metabolism.

Catabolism: Catabolism is the destructive phase of metabolism.

Energy requirements

Anabolism: Anabolism requires ATP energy.

Catabolism: Catabolism releases ATP energy.


Anabolism: Anabolism is an endergonic response.

Catabolism: Catabolism is an exergonic reaction.


Anabolism: Estrogen, testosterone, growth hormone, insulin, etc. are involved in anabolism.

Catabolism: adrenaline, cortisol, glucagon, cytokines, etc. are involved in catabolism.

Oxygen use

Anabolism: Anabolism is anaerobic; it doesn't use oxygen.

Catabolism: The catabolism is aerobic; it uses oxygen.

Effect on the body

Anabolism: Anabolism increases muscle mass. It shapes, repairs and nourishes the tissues.

Catabolism: Catabolism burns fat and calories. It uses up stored food to generate energy.


Anabolism: Anabolism is functional while resting or sleeping.

Catabolism: Catabolism is functional in body activities.

Energy conversion

Anabolism : In anabolism, kinetic energy is converted into potential energy.

Catabolism: In catabolism, potential energy is converted into kinetic energy.


Anabolism: Anabolism occurs during photosynthesis in plants, protein synthesis, glycogen synthesis, and assimilation in animals.

Catabolism: Catabolism occurs during cell respiration, digestion and excretion.


Anabolism: The synthesis of polypeptides from amino acids, glycogen from glucose and triglycerides from fatty acids are examples of the anabolic processes.

Catabolism: The breakdown of proteins into amino acids, glycogen into glucose and triglycerides into fatty acids are examples of catabolic processes.


Anabolism and catabolism can be collectively referred to as metabolism. Anabolism is a constructive process that uses energy in the form of ATP. It occurs in processes such as photosynthesis, protein synthesis, glycogen synthesis. Anabolism stores the potential energy in the body and increases body mass. Catabolism is a destructive process that releases the ATP that can be used during anabolism. It burns the stored complex molecules and reduces body mass. The main difference between anabolism and catabolism is the type of reactions involved in the two processes.

References: 1. "Metabolism." Wikipedia . Wikimedia Foundation, March 12, 2017. Web. March 16, 2017.

Image courtesy: 1. “Simple Photosynthesis Overview” By Daniel Mayer (mav) - Original imageVector version by Yerpo - Own work (GFDL) via Commons Wikimedia 2. “2503 Zellatmung” From OpenStax College - Anatomy & Physiology, Connexions website. June 19, 2013. (CC BY 3.0) via Commons Wikimedia

About the author: Lakna

Lakna, a graduate in molecular biology and biochemistry, is a molecular biologist and has a broad and strong interest in discovering things related to nature