The human body is composed of roughly 30 trillion cells that collectively perform the essential functions of life. The cells can perform these life-sustaining tasks with the help of several organic molecules present in them. These organic molecules are referred to as biomolecules.
The biomolecules have a wide range of sizes and structures, and they are involved in a vast array of life functions. They are composed of more than 25 naturally occurring elements, with the primary elements being carbon, hydrogen, oxygen, phosphorus, and sulfur.[1]
Carbon compounds have major involvement in the formation of biomolecules. They covalently bind with other elements to form several other compounds. Some biomolecules are considered derivatives of hydrocarbons, they’re formed by replacing hydrogen atoms from functional groups like alcohols, amines, aldehydes, ketones, and carboxylic groups.[1]
Given below is a list of small biomolecules and the macromolecules that are formed after the polymerization of these small monomer units.[1]
| Small Biomolecules | Macromolecules |
|---|---|
|
Sugars |
Carbohydrates |
|
Fatty acids |
Fats/lipids |
|
Amino acids |
Proteins |
|
Nucleotides |
Nucleic acids |
This article briefly explains the major biomolecules and the functions they perform in our bodies.
Approximately 10,000 to 100,000 molecules are present in a cell to regulate bodily function. But the four major types of biomolecules include carbohydrates, lipids, nucleic acids, and proteins. Most of the other compounds are derivatives of these major primary compounds.
Every biomolecule has its characteristics and is designated to perform some specific function essential for life. So, let’s see what they are all about!!!
Carbohydrates are a vital part of a healthy diet. They provide the energy required to do work. Scientifically, it’s a polyhydroxy aldehyde or polyhydroxy ketone.[1] Carbohydrates are the most abundant biomolecules on earth.
Depending on the number of products formed after hydrolysis, carbohydrates are classified into three groups.[1]
| No. | Disaccharides | Monomer units | Function |
|---|---|---|---|
|
1 |
Sucrose |
Glucose and Fructose |
It’s a product of photosynthesis |
|
2 |
Lactose |
Galactose and Glucose |
A major animal energy source |
|
3 |
Maltose |
Glucose and Glucose (alpha-1,4 linkage) |
Important intermediate in starch and glycogen digestion |
|
4 |
Trehalose |
Glucose and Glucose (alpha-1, alpha-1 linkage) |
An energy source for insects |
|
5 |
Cellobiose |
Glucose and Glucose (beta-1,4 linkage) |
Essential in carbohydrate metabolism |
|
6 |
Gentiobiose |
Glucose and Glucose (beta-1,6 linkage) |
A constituent of plant glycosides and some polysaccharides |
Proteins are unbranched polymers of amino acid residues. There are about 22 amino acids that are involved in the synthesis of proteins according to their location and function.[1] Proteins are categorized into four groups depending on their structural organization:
Proteins are essential components of organisms. It participates in almost every process within cells. It is involved in the processes of DNA replication, cell signaling, catalyzing metabolic reactions, construction of cell and tissue structures, and transportation of molecules from one place to another.[5]
Given below are eight groups of proteins that are categorized based on their functional properties.[6]
Nucleic acids are macromolecules present in cells and viruses, and they are involved in the storage and transfer of genetic information. The nucleic acid was first discovered by Friedrich Miesher in the nuclei of leukocytes.[1] Later, further studies showed that it’s a mixture of basic proteins and phosphorus-containing organic acid.
Structurally, nucleic acids are polymers of nucleotides (or polynucleotides) which are phosphate esters of nucleosides.[1] The nucleotides are comprised of three components:[1]
Based on nature, structure, and function, the nucleic acids are categorized into two groups: Deoxyribonucleic acids (DNA) and Ribonucleic acids (RNA).
DNAs are the hereditary material that resides inside the nucleus. In 1953, the first structure of DNA double helix (B-form of DNA) was discovered by Watson and Crick.[1] DNA has two other forms as well, A and Z forms. The conformation DNA will adopt depends on the hydration level, DNA sequence, chemical modification of the bases, the type, and concentration of a metal ion in the solution.[1]
The double helix structure represents two polynucleotides DNA coiled around a central helix. The two strands are antiparallel and interact by hydrogen bonds between complementary base pairs. In some cases, like at low pH, the triple helix form of DNA also exists. It’s formed by laying a third strand into the major groove of the DNA.
It is the genetic material that stores all the information required to be transferred to the progeny. It specifies the biological development of all living organisms and viruses.
RNA is present in all living cells. It has different roles to play in different organisms. It acts as genetic material in some viruses and has enzymatic activity in other organisms (where it is called ribozyme). Three types of RNA are present among organisms: rRNA, mRNA, and tRNA. All three have essential roles in the development and maintenance of life.
The importance of RNA and DNA is incomparable. DNA carrying the genetic information can’t leave its home, the nucleus, and this is why RNA exists. They are involved in the transfer of genetic information for protein synthesis via the processes of transcription and translation (outside the nucleus), and they control gene expression as well.[1]
Structurally, RNA exists in both single-stranded (primary structure) and double-stranded (secondary structure) forms.[1] The double-helical structure of RNA is present in the A form.
Lipids are organic compounds that are insoluble or poorly soluble in water but soluble in organic solvents (like dissolves like) such as ether, benzene, or chloroform.[1]
They are hydrophobic and structurally composed of a chain of hydrocarbons. They are chemically more diverse than other biomolecules, and they are primarily involved in membrane structure and energy storage.
Different classes of lipids include:
Other than these lipid molecules, some plasma lipoproteins also exist that are structurally a lipid-protein complex. These complexes function as lipid transport systems in blood. Some examples of lipoproteins are chylomicrons, low-density lipoproteins, and high-density lipoproteins.[1]
Biomolecules are vital for life as it aids organisms to grow, sustain, and reproduce. They are involved in building organisms from single cells to complex living beings like humans, by interacting with each other. The diversity in their shape and structure provides diversity in their functions.
The study of these biomolecules is known as biochemistry. Biochemistry deals with the study of their structures, functions, interactions, and reactions. Several functions of these biological molecules are still a mystery and current advanced techniques are being used to discover more molecules and understand their role in life-sustaining processes.
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