Difference Between Catabolism and Metabolism

Key difference - catabolism vs. metabolism

Catabolism and metabolism refer to a collection of biochemical reactions that take place in the body. Catabolism is the series of biochemical reactions that are involved in breaking down complex molecules in the body into small units. During catabolism, energy is released that can easily be used in other cellular processes. Metabolism is the set of biochemical reactions that take place within an organism, including catabolism. Anabolism is also included in metabolism. The main difference between catabolism and metabolism is that catabolism consists of destructive biochemical reactions that take place in the organism, while metabolism consists of the entirety of biochemical reactions in the organism, which can be either constructive or destructive.

This article examines

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

Difference Between Catabolism and Metabolism - Summary of Comparison

What is catabolism?

The series of reactions that break complex molecules down into small units is known as catabolism. Catabolism is a destructive process. Catabolic reactions release both heat and energy in the form of ATP . Therefore these reactions are seen as exergonic processes. The small molecule units produced in catabolism can either be used to release energy through oxidation or as precursors in other anabolic reactions. It is believed that catabolic reactions produce ATP energy, which is required by the anabolic reactions.

Catabolism also produces waste products such as urea, ammonia, lactic acid, acetic acid and carbon dioxide. Many hormones such as adrenaline, cortisol and glucagon are also involved in this process.

During digestion , complex macromolecules such as starch, fats and proteins are taken from food and broken down into small units such as monosaccharides, fatty acids and amino acids by digestive enzymes. These monosaccharides are then used in glycolysis to produce acetyl-CoA. This acetyl-CoA is used in the citric acid cycle and creates NAD +. ATP is made from NAD + by traversing the electron transport chain during oxidative phosphorylation. The catabolism of proteins , polysaccharides and fats is shown in Figure 1.

Key difference - catabolism vs. metabolism

Figure 1: Overview of protein, polysaccharide and fat catabolism

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.

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

What is Metabolism?

The totality of the biochemical reactions occurring in the body is collectively referred to as metabolism. There are three main phases in metabolism. First, during catabolism, carbohydrates , proteins, fats and nucleic acids in food are broken down into their small monomer units and nitrogenous wastes are eliminated. On the other hand, the resulting monomers such as glucose are used as substrates for cell respiration through energy production. Third, during anabolism, small monomer units are polymerized into complex molecules such as polypeptides, lipids, polysaccharides, and nucleic acids. Taken together, these biochemical reactions affect growth, development, structure maintenance, reproduction, and response to the external environment.

The metabolism takes place via metabolic pathways. This means that a chemical compound is converted into its end product of the metabolic pathway through a series of biochemical reactions. Each biochemical reaction is catalyzed by unique enzymes. Due to the presence of enzymes that catalyze every reaction, these reactions can be regulated in such a way that the organism receives the energy it needs. On the other hand, these enzyme-catalyzed reactions that require energy are coupled with spontaneous reactions that release the energy. The speed of metabolism depends on the amount of food consumed by the organism. The relationship between the metabolic pathways is shown in Figure 2 .

Difference Between Catabolism and Metabolism

Figure 2: Relationship between metabolic pathways

Difference Between Catabolism and Metabolism


Catabolism: The series of biochemical reactions that are involved in the energy release processes in organisms referred to as catabolism.

Metabolism: The totality of the biochemical reactions in the body is called metabolism.


Catabolism: Catabolism involves the destructive reactions in the body.

Metabolism: Metabolism includes both constructive and destructive reactions in the body.


Catabolism: The release of energy from the metabolism drives cell processes and heats the body while allowing the muscles to move.

Metabolism: Metabolism is important for the growth, development and maintenance of cell structures and the reaction to the environment.

Form of energy

Catabolism: Reactions are involved in both energy release and energy storage processes.

Metabolism: In catabolism, potential energy is released as kinetic energy .


Catabolism: Catabolism is an exergonic reaction.

Metabolism: The metabolism consists of endergonic and exergonic reactions.

Oxygen use

Catabolism: Catabolism is aerobic, uses oxygen for the process.

Metabolism: Metabolism consists of both aerobic and anaerobic reactions.


Catabolism: Hormones such as adrenaline, cortisol, glucagon and cytokines are involved in catabolism .

Metabolism: At the metabolism anabolic hormones such as estrogen, testosterone, growth hormone and insulin and catabolic hormones are involved.

Effect on the body

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

Metabolism: Metabolism enables growth, development, maintenance of structure, reproduction and reaction to the external environment.


Catabolism: Catabolism is functional during physical activity.

Metabolism: The metabolism is functional when resting as well as when sleeping and during physical activities.

Energy conversion

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

Metabolism: Metabolism is a conversion between potential and kinetic energy.


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

Metabolism: Metabolism takes place during photosynthesis in plants, protein synthesis, glycogen synthesis, digestion, respiration and excretion.


Catabolism: Anabolic processes like photosynthesis and catabolic processes like cellular respiration are examples.

Metabolism: digestion, cellular respiration and excretion are examples of the catabolic processes.


Catabolism and metabolism are terms that summarize biochemical reactions in the body. Metabolism refers to the totality of biochemical reactions in the body. It includes both catabolism and anabolism, which retain all the characteristics that make up an organism. Metabolism influences the growth, development, reproduction and reaction of an organism to the external environment. Catabolism comprises the biochemical reactions that break down complex molecules into their small units. The main difference between catabolism and metabolism is their relationship between them.

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

Image courtesy of: 1. “Catabolism Scheme” by Tim Vickers, vectorized by Fvasconcellos - w: Image: Catabolism.png (Public Domain) via Commons Wikimedia 2. “Metabolic Pathways (partially labeled)” By Fred the Oyster (CC BY -SA 4.0) 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