Difference Between Primary and Secondary Metabolites

Main Difference – Primary vs Secondary Metabolites

Metabolism is the collection of chemical processes that occurs in living organisms in order to maintain life. Thousands of chemical compounds are involved in the metabolism of living organisms. These compounds are called metabolites and they are intermediates and products of metabolism. Primary metabolites and secondary metabolites are the two categories of metabolites found in living organisms. Both of them are small molecules, which act as signaling molecules, catalysts, stimulators, or inhibitors for any metabolic activity in the body. The main difference between primary metabolites and secondary metabolites is that primary metabolites are directly involved in primary growth development and reproduction whereas secondary metabolites are indirectly involved in metabolisms while playing important ecological functions in the body.

Key Areas Covered

1. What are Primary Metabolites
      – Definition, Types, Function
2. What are Secondary Metabolites
      – Definition, Types, Function
3. What are the similarities between Primary and Secondary Metabolites
      – Common Features
4. What is the difference between Primary and Secondary Metabolites
      – Comparison of Key Differences

Key Terms: Metabolism, Metabolites, Primary Metabolites, Secondary Metabolites, Chemical Compounds, Living Organisms, Growth, Development, Reproduction 

What are Primary Metabolites

Primary metabolites are small chemical compounds that are directly involved in the growth, development, and reproduction of living organisms. Therefore, they are key components in the maintenance of normal physiological functions in the body. Thus, primary metabolites are often referred to as central metabolites. Primary metabolites are usually formed during the growth phase due to energy metabolism. They are major components of proper growth. Ethanol, lactic acid, nucleotides, vitamins, and some amino acids are considered as primary metabolites. In industrial microbiology, ethanol is the most common primary metabolite produced in large-scale by fermentation. Additionally, amino acids like L-lysine and L-glutamate are produced in large-scale. Citric acid is the other common primary metabolite produced in large-scale. It is used as an ingredient in food production.

Types of Primary Metabolites

Figure 1: Glutamic Acid

What are Secondary Metabolites

Secondary metabolites are small organic compounds produced through the modification of primary metabolites. They are formed near the stationary phase of growth. Secondary metabolites do not play a role in growth, development, or reproduction. However, they play a role in ecological functions like defense mechanisms, serve as antibiotics, and produce pigments. Atropine and antibiotics like erythromycin and bacitracin are commercially important secondary metabolites produced in large-scale. Atropine serves as a competitive antagonist for acetylcholine receptors. It is derived from various plants which can be used to treat bradycardia. Erythromycin is an antibiotic with wide antimicrobial spectrum.

Types of Secondary Metabolites

Figure 2: Morphine

Similarities Between Primary and Secondary Metabolites

• Both primary and secondary metabolites are small chemical compounds which serve as signaling molecules, catalysts, stimulators or inhibitors for a particular chemical reaction.

Difference Between Primary and Secondary Metabolites

Definition

Primary Metabolites: Primary metabolites are a category of metabolites which are directly involved in the growth, development, and reproduction.

Secondary Metabolites: Secondary metabolites are compound which are not directly involved in the normal growth and development but, have some ecological functions in the body.

Significance

Primary Metabolites: Primary metabolites perform physiological functions in the body like intrinsic functions.

Secondary Metabolites: Secondary metabolites are derivatives of primary metabolites.

Involved in

Primary Metabolites: Primary metabolites are directly involved in the growth, development, and reproduction.

Secondary Metabolites: Secondary metabolites play a role in ecological functions such as helping in the defense mechanisms, serving as antibiotics, and producing pigments.

Formation

Primary Metabolites: Primary metabolites are formed during the growth phase due to the energy metabolism.

Secondary Metabolites: Secondary metabolites are formed near the stationary phase of growth.

Quantity and Extraction

Primary Metabolites: Primary metabolites are produced in large quantities. Therefore, the extraction of primary metabolites is easy.

Secondary Metabolites: Since secondary metabolites are produced in small quantities, their extraction is difficult.

In Plants

Primary Metabolites: Primary metabolites are same in all plants.

Secondary Metabolites: Different secondary metabolites are unique to different plant species.

Basic Molecular Structure

Primary Metabolites: Primary metabolites are a part of the basic molecular structure of an organism.

Secondary Metabolites: Secondary metabolites are not a part of the basic molecular structure of an organism.

Role

Primary Metabolites: Primary metabolites are highly useful to organisms.

Secondary Metabolites: The absence of secondary metabolites does not show any significant change in the metabolism.

Examples

Primary Metabolites: Ethanol, lactic acid, nucleotides, vitamins, and some amino acids are primary metabolites.

Secondary Metabolites: Pigments, antibiotics, and drugs are secondary metabolites.

Conclusion

Primary metabolites and secondary metabolites are the two types of metabolites found in living organisms. Primary metabolites are directly involved in the growth, development, and reproduction of organisms. In contrast, secondary metabolites do not show a considerable change in their presence or absence in metabolic reactions. This is the main difference between primary and secondary metabolites. Both primary and secondary metabolite are small organic compounds.

Reference:

1. “Primary and Secondary Metabolites – Boundless Open Textbook.” Boundless. N.p., 26 May 2016. Web. Available here. 06 June 2017. 
2. “Primary and Secondary.” GradeStack Courses. N.p., n.d. Web. Available here. 06 June 2017. 

Image Courtesy:

1. “Glutaminsäure – Glutamic acid” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia
2. “Morphin – Morphine” By NEUROtiker – Own work (Public Domain) via Commons Wikimedia