Anabolism vs Catabolism- Definition, 13 Key Differences, Examples

Last Updated on March 10, 2021 by Sagar Aryal

Anabolism Definition

Anabolism is a set of enzyme-catalyzed reactions that synthesize relatively complex molecules from simple structures in living systems.

  • Anabolism is also called biosynthesis as it is involved in the formation of various compounds that are then used as cell components as well as energy.
  • The process of anabolism requires energy; thus, it is an endergonic process, and the primary source of energy is solar energy.
  • Anabolism is a part of metabolism where organic substances are formed so that they can be used later for energy.
  • Reactions in anabolism occur in a step-by-step process so as to increase the organic content of the cell, which is essential for growth.
  • In a non-growing cell, the process of anabolism is balanced by catabolism, but in growing cells, anabolic processes often dominate over catabolic reactions.
  • The process of anabolism occurs in three distinct stages: In the first stage, monomers like monosaccharides and amino acids are formed. In the second stage, the monomers are activated by providing energy. In the final stage, the reactive monomers are assembled into complex molecules like polysaccharides and proteins.
  • The overall process of anabolism differs in different groups of living beings. Autotrophs can synthesize complex molecules starting with single carbon precursors like carbon dioxide, but heterotrophs utilize the monomers from autotrophs to synthesize organic polymers.
  • Anabolism is powered by catabolism where the energy obtained from catabolism is used for anabolism.
  • The most important process in anabolism is polymerization, where monomeric units are linked together to form polymeric units.
  • Anabolism is regulated by enzymes that undergo irreversible steps at some point in the pathways to ensure that biosynthesis doesn’t occur in an infinite loop.
  • Anabolic processes include pathways like photosynthesis, amino acid biosynthesis, and gluconeogenesis which are essential for the built-up of organs and tissues and their differentiation.
Anabolism vs Catabolism
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Catabolism Definition

Catabolism is a set of enzyme-catalyzed reactions that breakdown large complex molecules into smaller units in living systems.

  • The most important aspect of catabolism is the release of energy which is stores in the body in the form of ATP. 
  • It is a destructive process consisting of different exergonic reactions that result in the release of energy.
  • In addition to energy and units for anabolic reaction, catabolism also produces cellular wastes like urea, carbon dioxide, ammonia, lactic acid, etc.
  • Catabolism is the breaking-down part of the metabolism which provides energy as well as resources for anabolism.
  • The process of catabolism occurs in three distinct phases: In the first stage, large complex molecules are broken down into smaller particles where a small amount of energy is released in the form of heat.
  • In the second stage, the smaller molecules are oxidized, releasing energy to form ATP. In the final stage, the molecules are oxidized to carbon dioxide via the Krebs cycle
  • Catabolism might differ in different living systems based on the utilization of organic compounds as a source of carbon or electron donor. 
  • Heterotrophs break down larger organic molecules in order to generate energy, whereas organotrophs generate energy by producing electrons from the breakdown of organic molecules.
  • The most important catabolic process in living systems is cellular respiration where intermediate molecules from various other pathways meet to generate a large amount of energy.
  • In growing cells, catabolism is often dominated by anabolism, but catabolism is essential for the release of energy required for the growth of the living system.
  • Catabolism, like anabolism, is regulated by a set of enzymes that make sure to prevent excessive catabolic reactions.
  • Catabolic reactions occur when the body is active and requires energy to perform different living activities.

13 Major Differences (Anabolism vs Catabolism Table form)

Characteristics Anabolism Catabolism
Definition Anabolism is a set of enzyme-catalyzed reactions that synthesize relatively complex molecules from simple structures in living systems. Catabolism is a set of enzyme-catalyzed reactions that breakdown large complex molecules into smaller units in living systems.
Role in metabolism Anabolism is the constructive phase of metabolism. Catabolism is the destructive phase of metabolism.
Process In anabolism, large complex molecules are synthesized from smaller molecules. In catabolism, large molecules are broken down to form smaller molecules.
Energy Anabolic reactions require a considerable amount of energy. Catabolic reactions release a considerable amount of energy.
Reaction Anabolic reactions are endergonic reactions. Catabolic reactions are exergonic reactions.
Role of oxygen Oxygen is not required for anabolic processes. Catabolic processes require oxygen as most of the reactions are oxidation reactions.
Energy conversion During anabolism, kinetic energy in the body is converted to potential energy. During catabolism, potential energy is converted into kinetic energy.
Occurs during Anabolic processes usually occur when the body is at rest or asleep. Catabolic processes usually occur when the body is active and requires energy.
Hormones involved Hormones like estrogen, testosterone, growth hormones, and insulin are involved in anabolism. Hormones like adrenaline, cortisol, glucagon, and cytokines are involved in catabolism.
Growing cells In growing cells, anabolism dominates over catabolism. Catabolic reactions are less prevalent than anabolic reactions in growing cells.
Effects on exercise Anabolic reactions are often anaerobic in nature and result in a build-up of muscle mass. Catabolic reactions are aerobic and result in burning fat and calories during exercise.
Primary function Anabolism is essential for the growth and maintenance of living systems. Catabolism is essential to perform different activities in living systems.
Examples Processes like photosynthesis, protein biosynthesis, and assimilation are some examples of anabolic processes. Processes like cellular respiration, digestion, and excretion are some examples of catabolic processes.

Examples of anabolism

Protein biosynthesis

  • Protein biosynthesis is an anabolic process where smaller molecules like amino acids are linked together to form peptides and proteins.
  • Protein biosynthesis is the process of synthesis of proteins that perform different functions in living systems.
  • The process of protein biosynthesis occurs in two pages; transcription and translation.
  • During transcription, a strand of mRNA is formed from DNA which contains the codes for the resulting protein.
  • Transcription is followed by translation, where the mRNA moves to the ribosomes that read the sequence on the mRNA.
  • Based on the sequence, tRNA brings amino acids to the ribosomes in the correct sequence to form a protein molecule.
  • The proteins formed by this process are used for different purposes like a build-up of body mass, regulation of chemical reaction (enzymes), etc.
  • Protein biosynthesis is anabolic as it results in the formation of proteins that are essential for the growth and maintenance of the living system.

Examples of catabolism

Cellular respiration

  • Most living organisms utilize glucose as a source of energy which is broken down into smaller units in order to release energy.
  • The glucose is stored in the body in different forms, which are then broken down so that it can enter cellular respiration.
  • Cellular respiration requires oxygen as it is an oxidation process and occurs within each cell leading to the release of a large amount of energy and carbon dioxide.
  • Cellular respiration consists of a set of catabolic reactions, all of which are catalyzed by different enzymes.
  • Cellular respiration is one of the most important processes in catabolism as it produces various intermediates like acetate and pyruvate that can be utilized in anabolic processes.

References and Sources

  • Jain JL, Jain S and Jain N (2005). Fundamentals of Biochemistry. S. Chand and Company.
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