Anabolism | Definition, Functions, and Types

Anabolism| Definition, Functions, and Types

Anabolism Definition

Anabolism is the metabolic process that results in larger molecules from smaller ones. Anabolic processes require energy, while catabolic reactions provide the necessary energy for anabolism. Anabolism is a sequence of enzyme-catalyzed reactions that build larger molecules from smaller ones. Anabolic processes produce more complex substances from simpler ones, whereas catabolic processes break down complex substances into simpler components.

Anabolism always involves the same two phases: an energy-releasing or exergonic phase to drive the reaction forwards and an energy-requiring or endergonic phase, which occurs after the exergonic phase. Anabolic reactions are caused by energy-rich phosphate groups attached to an energy source, adenosine triphosphate (ATP).


Function of Anabolism

Anabolism serves five main parts:

  1. Anabolism provides the means for an increase in cell size. Anabolic processes result in the growth of cells and tissues, whereas catabolic processes break down cells and tissues to liberate energy and release nitrogenous waste as urea and ammonia. An essential aspect of anabolism is that it almost always requires energy input. Anabolic processes are powered by ATP, which is first hydrolyzed into adenosine diphosphate (ADP) and inorganic phosphate (Pi) to release energy that can be used to drive anabolism. Anabolism may also require using other high-energy compounds such as creatine phosphate, which can donate its phosphate group to ADP to form ATP.
  2. Anabolism is necessary for the maintenance of cell structure. Anabolic processes are responsible for producing new proteins and the replacement of damaged proteins. Damaged proteins must be replaced if cells are to continue functioning correctly.
  3. Anabolism provides the means for an increase in the complexity of cell structure. Anabolic processes are responsible for synthesizing new DNA, RNA, and lipids. These molecules are necessary for the growth and maintenance of cells.
  4. Anabolism is necessary for the reproduction of cells. Anabolic processes are responsible for the synthesis of new cells and the replacement of old cells, which die through apoptosis. Anabolism is also accountable for producing gametes (sex cells) in animals and for regenerating plant parts that have been damaged or removed.
  5. Anabolism involves the synthesis of complex molecules from simpler ones during the biosynthesis of various compounds in plants and animals. Anabolic processes are used to synthesize carbohydrates, lipids, proteins, and nucleic acids. Anabolism is often coupled with catabolism in that one substance (the substrate) is broken down into simpler components that become the building blocks for other molecules.

Examples of Anabolic Processes

  1. Protein Anabolism 

The synthesis of proteins from amino acids is an anabolic process. Proteins are the largest and most complex molecules in cells. They serve various functions, including the structure and function of cells and tissues, the transport of substances within and between cells, and the catalytic activity of enzymes.

2. Biosynthesis of Proteins, Carbohydrates and Lipids

The biosynthesis of carbohydrates, lipids, and nucleic acids is an anabolic process. Carbohydrates provide cells with energy through glycolysis and the citric acid cycle. Lipids are used for membrane synthesis, insulation, thermal regulation, and the storage of chemical energy in the form of triglycerides. Nucleic acids contain genetic information for all living organisms. Different types of nucleic acids are used in different cells to replicate, copy, and translate genetic information.

3. DNA synthesis and Replication

The duplication and synthesis of deoxyribonucleic acid (DNA) is an anabolic process. Anabolism is used to replicate chromosomes during all phases of the cell cycle, except for the resting phase (G0). Anabolic processes are necessary for DNA replication because Phosphodiester bonds must be formed to synthesize the new DNA.

4. RNA synthesis

The synthesis of ribonucleic acid (RNA) is an anabolic process that occurs in the cytoplasm of cells. RNA is a nucleic acid that contains the genetic information for protein synthesis. The RNA molecule comprises a sugar, a phosphate group, and a nitrogenous base. There are four types of nitrogenous bases in RNA: adenine (A), guanine (G), cytosine (C), and uracil (U).

5. Translation of RNA into Protein

The translation of RNA to protein is an anabolic process. The sequence of codons in the RNA molecule is read by a transfer RNA (tRNA) protein. The tRNA binds to specific amino acids and brings them to the ribosomes, assembled into a protein.

6. Regeneration of Plant Parts

The regeneration of plant parts is an anabolic process. Plant parts can be damaged or removed, but they will regenerate if the necessary conditions are provided. Anabolism is used to regenerate parts such as stems, leaves, and flowers. Anabolic processes are responsible for replacing old cells and tissues with new ones in plants.

7. Growth of Bones and Muscles

The growth of bones and muscles is an anabolic process. Bones and muscles are composed of cells that are constantly regenerating. Anabolism is responsible for synthesizing new cells and replacing old cells in bones and muscles. Anabolic processes are also necessary for the growth of these tissues.

Hypertrophy is an increase in the size of cells and muscles. Anabolic processes cause hypertrophic growth as a result of cellular growth. Hyperplasia is an increase in the number of cells due to cell division. Anabolic processes also cause hyperplastic growth due to mitosis during cell division. Anabolic processes are needed to produce hyperplastic growth because the cells must be synthesized during cell division.

8. Anabolic Steroids

Anabolic steroids are synthetic hormones similar to the male sex hormone testosterone. Anabolic steroids are used to promote muscle growth, strength, and aggressiveness. Most professional sports organizations ban anabolic steroids because they provide an unfair advantage to athletes who use them. Anabolic steroids stimulate anabolism by increasing protein synthesis and the frequency of muscle cells. Anabolic steroids may also promote hyperplasia because they cause the body to produce more testosterone, which can cause increases in muscle mass.

Anabolic steroids treat hormone deficiencies, such as low testosterone levels. Anabolic steroids are also used to treat diseases of the endocrine system, such as diabetes mellitus and Cushing’s syndrome. Anabolic steroids are effective in treating these diseases because they stimulate anabolism. Anabolic steroids have many side effects, including liver damage, sterility, and heart disease.