Dictionary > Micromolecule


micromolecule definition and examples

n., plural: micromolecules
[ˈmaɪ.kɹoʊ ˈmɒləkjuːl]
Definition: a molecule of relatively small size and low molecular weight as opposed to a macromolecule, which is large and with greater molecular weight.

Micromolecules Definition

How to define micromolecule? Micromolecules are relatively small molecules that are combined together to form a macromolecule. Micromolecules have low molecular weight and contain a small number of atoms. Micromolecules regulate different biological processes.

What is micromolecule? The word micromolecule refers to a small molecule of low molecular weight and is often referred to as a monomer. Monomers are combined together through different biochemical reactions to form a macromolecule, which is known as a polymer. Unlike micromolecules, macromolecules are relatively larger molecules with a high molecular weight. Macromolecules are made up of small micromolecules known as monomers bonded together. Therefore, micromolecules are monomers forming a polymer macromolecule. For example, proteins are made up of monomers of amino acids.

Cells are composed of various molecules. The interaction between different types of molecules maintains the proper structure and function of the cell. Molecules in the cell participate in various biochemical processes inside the cell to maintain the cell. These molecules can also join together to form complex compounds known as macromolecules. The most important examples of macromolecules in a cell are nucleic acids, proteins, carbohydrates, and lipids. They are made up of small repetitive micromolecules. The most essential micromolecules in cells are nucleotides, amino acids, monosaccharides, fatty acids, and glycerol.

Other inorganic essential micromolecules are minerals and water. Micromolecules are found either free as water or joined together forming a macromolecule such as proteins, carbohydrates, and nucleic acids. Micromolecules are combined together forming macromolecules by different types of reactions like addition reactions where micromolecules are added one by one. Another reaction is the condensation reaction where a water molecule is lost from two micromolecules after combination.

Micromolecules are produced from metabolic processes. Moreover, they are important substrates for different reactions.

In order to maintain the health of our bodies, we should get a balanced diet that includes the recommended amounts of micromolecules and macromolecules. Food labels provide the amounts of nutrients found in each package. You should get different foods to get a wide range of nutrients in your diet.

micromolecules - types
Figure 1: Micromolecules are combined together in the form of linkage to form macromolecules or polymers. Amino acid micromolecules form proteins, fatty acids micromolecules form lipids, sugar micromolecules form glycerol and carbohydrates, while nucleobases micromolecules form DNA and RNA. Credit: Courses.lumenlearning.com
Micromolecule (biology definition): a molecule that is relatively smaller (than a macromolecule), or of low molecular weight that may regulate a biological process. Examples of micromolecules are the monomers (e.g. nucleotides, amino acids, monosaccharides, glycerol, and fatty acids) and inorganic compounds (e.g. water and minerals). Etymology: from Ancient Greek “μικρός” (“mikrós”), meaning “small” and from New Latin “molecula” (“a molecule”). Compare: macromolecule

Micromolecule Examples

Biological micromolecules are present naturally in the body. They are essential for life. Examples of micromolecules are sugars, amino acids, nucleic acids, fatty acids, water, and minerals.


Sugars are combined together forming carbohydrates. Sugars contain only carbon, oxygen, and hydrogen. Glucose is one of the most important micromolecules that form carbohydrates. It may be found in the form of a ring (cyclic glucose) or an open-chain (acyclic glucose). In plants, glucose micromolecule is produced during photosynthesis where carbon dioxide and water produce glucose and oxygen in a biochemical reaction. Then, the glucose is stored in the plant in various ways. It may be polymerized forming carbohydrates such as starch that animals and other organisms can feed on.

Glucose micromolecules are a major source of energy for plants, and also for other organisms and animals that feed on plants. It plays a vital role in the cellular respiration reaction that takes place in living organisms. During the reaction, oxygen and glucose react in a reaction producing water, carbon dioxide, and adenosine triphosphate (ATP). ATP is used by all cells to get energy since it is the main source of energy for living cells.

photosynthesis and cellular respiration in plants
Figure 2: photosynthesis and cellular respiration in plants

Micromolecular form of sugars is the only form that produces energy. Food usually contains complex carbohydrates, not glucose micromolecules. Therefore, bodies of living organisms break down carbohydrate polymers to glucose monomers in order to get ATP to produce energy during cellular respiration.

Starch is made up of long chains of glucose micromolecules. Therefore, foods rich in starch are a great source of energy such as potato which is rich in starch and provides a great source of energy for living cells. In plants, starch is used in storing excess glucose in the plant. While in animals, excess glucose is stored in the form of glycogen, not starch.

READ: Sugar Homeostasis in Humans – Biology Tutorial

Amino acids

Amino acid is a monomer that makes up proteins. There are 20 amino acids micromolecules. Amino acids are organic molecules containing an amino group, a hydroxyl group, and a carbon side chain. All amino acids share the same basic structure; however, they differ in their carbon side chain. Amino acids micromolecules vary in terms of polarity, charge, molecular weight, and functions. Amino acids are either non-essential or essential where non-essential amino acids are synthesized inside the human body from glucose mainly so it is not essential to get them from the diet. Whereas essential amino acids are not synthesized inside the body so they must be obtained from the diet.

Polypeptide Sequences
Figure 3. Polypeptide Sequences. Credit: NIH.

Amino acid micromolecules are joined together in biochemical reactions to form proteins. Proteins are very important for living organisms since they have a supporting function, storage function, and transporting function. Proteins act as enzymes and hormones, they support bones, help in growth and development, maintain the pH of the body, maintain the balance of fluids, protect the body from infections, transport nutrients in the blood, and provide energy.

Amino acid micromolecules are joined together by peptide bonds to form polypeptide chains that are combined together to form a protein. Proteins vary in their chain length, sequence of amino acids, properties, and function. The great variety between different proteins results from the endless combinations of different amino acids.

Proteins have different functions. The structural proteins in connective tissues of animals contain collagen which is a structural protein forming feathers, hair, and horns. Storage proteins store energy such as albumin in eggs and proteins in seeds of plants. Transport proteins such as hemoglobin transport substances in the body. Hemoglobin transports oxygen to all body cells and transports carbon dioxide to the two lungs for gas exchange. Hormonal proteins regulate different activities of the body. For example, the insulin hormone regulates the level of sugar in the blood. Enzymes are proteins that speed up chemical reactions in the body. For example, enzymes are responsible for the digestion of foods to allow the body to get energy.

READ: Protein Activity and Cellular Metabolism – Biology Tutorial

Fatty acids

Fatty acids provide energy to the body, protect internal organs, form cellular membranes, control blood pressure and cholesterol, and help in the absorption of fat-soluble minerals such as vitamins A, K, E, and D. Fatty acids are micromolecules that form fats when combined together. There are two types of fats, saturated and unsaturated fats.

Saturated fats are bad fats found in processed and baked foods such as desserts, cookies, and pizza. It is also found in animal products such as dairy products, pork, and beef. Saturated fats are unhealthy and should be taken in small amounts.

On the other hand, unsaturated fats are healthier. Saturated fats are usually found in hazelnuts, peanut butter, almonds, pumpkin seeds, sunflower seeds, and avocados. It is also found in oils extracted from plants like peanut oil, sesame oil, and olive oil.

Fatty acids influence cholesterol levels in the blood; therefore, we should limit the consumption of saturated fats and increase the consumption of unsaturated fats since saturated fats found in processed and baked foods increase the risk of strokes, cardiovascular diseases, and obesity. While unsaturated fats keep our brain healthy and decrease the risk of developing Alzheimer’s disease.

Nucleic acids

Nucleic acids are extremely important micromolecules. They are combined together to form DNA which provides the genetic material for every individual. DNA controls different sequences of amino acids and how they are arranged to form proteins. Another macromolecule composed of nucleic acid micromolecules is RNA. Nucleotides are monomers made up of three parts: a phosphate group, a nitrogenous base, and sugar. The DNA is a double-stranded polymer while RNA is a single-stranded polymer of nucleotides.

Schematic diagram of DNA structure. Credit: Zephyris , CC BY-SA 3.0.

Schematic diagram of DNA structure
Schematic diagram of DNA structure. Credit: Zephyris , CC BY-SA 3.0


Water is an inorganic micromolecule. It is found in its free form. Water contains two hydrogen atoms and one oxygen atom only. Water is essential for every living organism since most of the bodyweight is made up of water. Also, water has various important functions such as removing waste from the body, controlling the temperature of the body, and improving the function of the brain. Water is being consumed either directly by drinking water or indirectly by eating foods that contain large amounts of water like fruits and vegetables. Water helps in the production of saliva, it acts as a lubricant that protects joints, spinal cord, and tissues from friction as well as inflammation, water improves the physical performance of the body, it prevents constipation and maintains a regular bowel movement, water can also help in digestion and absorption of various nutrients, it helps in weight loss, improves the blood circulation, decreases illness and infections, improves cognitive functions, boosts energy and improves mood. Drinking water prevents dehydration, thus it brightens the skin.


Is water a macromolecule? No, water is an important micromolecule found in its free form. Even though water is not a macromolecule, water helps in the formation of macromolecules since it is involved in interactions producing macromolecules.


Minerals are essential micromolecules that maintain the health of the body. Minerals keep the muscles, heart, bones, and brain functioning properly. Moreover, they are important for synthesizing hormones and enzymes. Also, they are important for activating some enzymes for biochemical reactions. Minerals are needed in certain amounts where some minerals such as phosphorus, sulfur, chloride, calcium, potassium, and sodium are required in large amounts. Whereas trace minerals like copper, iron, zinc, selenium, iodine, cobalt, and fluoride are needed in small amounts only, and taking them in large amounts might harm the body. Minerals are found in various foods or as supplements.

READ: A Balanced Diet – Minerals and Proteins

Try to answer the quiz below to check what you have learned so far about micromolecule.


Choose the best answer. 

1. What is a micromolecule?

2. Micromolecules of proteins

3. Micromolecules of carbohydrates

4. Form lipids when combined together

5. All of the following are micromolecules except for:

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  • Admin. (2021, June 9). What is a Monomer? – Definition, Classification, Examples with Videos. BYJUS. https://byjus.com/chemistry/monomers/.
  • Biological macromolecules. OpenStax CNX. (n.d.). https://cnx.org/contents/49PF5FCK@2.1:dDWDbEU-@1/Biological-macromolecules.
  • Caglioti, L., & Righi, V. (2017). Macromolecular Versus Micromolecular World. In Advances in Asymmetric Autocatalysis and Related Topics (pp. 111-117). Academic Press.‏”
  • Know the facts about fats. Harvard Health. (2021, April 19). https://www.health.harvard.edu/staying-healthy/know-the-facts-about-fats.
  • Silver, N. (2020, July 1). Why Is Water Important? 16 Reasons to Drink Up. Healthline. https://www.healthline.com/health/food-nutrition/why-is-water-important.
  • Team, V. C. (2020, October 12). Cellular micromolecules. Cellular micromolecules are A Amino acids Water Minerals class 12 biology CBSE. https://www.vedantu.com/question-answer/cellular-micromolecules-are-a-amino-acids-water-class-12-biology-cbse-5f84bf99ff09b973ea5c4151.
  • U.S. National Library of Medicine. (2021, June 28). Minerals. MedlinePlus. https://medlineplus.gov/minerals.html.
  • Walle, G. V. D. (2018, June 20). 9 Important Functions of Protein in Your Body. Healthline. https://www.healthline.com/nutrition/functions-of-protein.

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