Anabolism and Catabolism – Definitions and Differences

Anabolism and Catabolism
Anabolism is the part of metabolism that builds large molecules from smaller ones. Catabolism is the part of metabolism that breaks large molecules into smaller ones. Catabolism yields energy that fuels anabolism.

Metabolism consists of two sets of biochemical pathways called anabolism and catabolism. Anabolism builds complex molecules from simpler ones, while catabolism breaks larger molecules into smaller ones. Anabolism and catabolism go hand-in-hand, as each makes the source material for the other. Anabolism requires energy, while catabolism produces energy that fuels anabolism.

Differences Between Anabolism and Catabolism

There are several key differences between anabolism and catabolism:

Builds complex molecules from simpler onesBreaks complex molecules into smaller ones that are easier to absorb or excrete
Requires energy (endothermic)Releases energy (exothermic); Often spontaneous
Converts kinetic energy into potential energy (e.g., weightlifting)Converts potential energy into kinetic energy (e.g., aerobic exercise)
Uses hormones including adrenalin, glucagon, and cortisolUses insulin and anabolic steroids
Builds proteins, nucleic acids, glycogen, triglyceridesBreaks larger molecules into amino acids, glucose, fatty acids, carbon dioxide, water
Used for growth, repair, and energy storagePerforms several activities, including thermoregulation, energy supply, digestion
Differences between anabolism and catabolism

Anabolism and Catabolism Examples

Anabolic processes make proteins, repair damage, and grow tissues. Here are examples of anabolic processes and their chemical reactions:

  • Glycerol reacts with fatty acids to make lipids:
  • Simple sugars combine to form disaccharides and water:
    C6H12O6 + C6H12O6   →  C12H22O11 + H2O
  • Amino acids join together to form dipeptides, which act as the building blocks of proteins:
  • Carbon dioxide and water react to form glucose and oxygen in photosynthesis:
    6CO2 + 6H2O  →  C6H12O6 + 6O2
  • Weightlifting and other anaerobic exercises are anabolic processes. This type of exercise promotes muscle repair and growth.

Catabolism breaks down complex molecules into simpler ones that are more useful to the cell. Sometimes, it breaks down molecules so they are easier to dispose of as waste in the form of carbon dioxide, ammonia, acetic acid, lactic acid, and urea. Catabolism generates heat and may produce chemical energy, often in the form of ATP. The energy may drive anabolism or help regular body temperature. Here are some examples of catabolic processes and their reactions:

  • During cellular respiration, glucose and oxygen react to yield carbon dioxide and water
    C6H12O6 + 6O2  →  6CO2 + 6H2O
  • In cells, hydroxide peroxide decomposes into water and oxygen:
    2H2O2  →  2H2O + O2
  • Aerobic exercise, such as a cardio workout is a catabolic process. Fat (or muscle) releases heat and carbon dioxide as it is broken down.
  • Proteins break into amino acids
  • Lipids break into fatty acids
  • Nucleic acids break into nucleotides
  • Polysaccharides break into disaccharides and monosaccharides

Anabolism and Catabolism Hormones

Hormones play an important role in metabolism. Some hormones are associated with anabolism or catabolism:

Anabolic hormones include insulin and the anabolic steroids:

  • Estrogen
  • Human growth hormone
  • Insulin
  • Testosterone

Catabolic hormones include:

  • Adrenaline
  • Cortisol
  • Cytokines
  • Glucagon
  • Melatonin
  • Orexin (Hypocretin)

Amphibolic Pathways

An amphibolic pathway is a metabolic pathway that can be either anabolic or catabolic, depending on the availability of energy. These pathways either produce energy or consume it to make products, depending on the needs of the cell. Examples of amphibolic pathways are the citric acid cycle and glyoxylate cycle.


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