What is a biomolecule?

Biomolecules are substances produced by cells and living organisms, exhibiting diverse sizes, structures, and functions. The primary types include carbohydrates, lipids, nucleic acids, and proteins. Nucleic acids (DNA and RNA) uniquely store an organism’s genetic code, determining the amino acid sequence of proteins. Proteins are structural components, transporters, enzymes, catalysts, antibodies, and hormones. Carbohydrates are key energy sources and structural components, built from sugar units. Lipids serve as stored energy, chemical messengers, and membrane components, separating cells and creating organelles. All biomolecules share a structure-function relationship influenced by their environment.

What are the main types of biomolecules?

Biomolecules are substances produced by cells and living organisms, displaying a vast array of sizes, structures, and functions. The four main types are carbohydrates , lipids , nucleic acids , and proteins .

Why are biomolecules important for living things?

Biomolecules are crucial for living organisms due to their vast array of functions. The four major types are carbohydrates, lipids, nucleic acids, and proteins. Carbohydrates are essential energy sources and structural components. Lipids provide stored energy, act as chemical messengers, and form membranes that separate cells. Nucleic acids (DNA and RNA) uniquely store an organism’s genetic code, determining the amino acid sequence of proteins. Proteins are major structural elements, transport nutrients, catalyze reactions, form antibodies and hormones, and influence gene activity. The conversion of carbon dioxide into carbohydrates by green plants, using light energy from the Sun, is an essential process that has permitted the evolution of life as it now exists.

What roles do proteins play as biomolecules?

Proteins are complex biomolecules essential to all living organisms and hold immense nutritional value as they directly participate in the chemical processes that sustain life.

How do carbohydrates and lipids differ in structure and function?

Carbohydrates and lipids both serve as crucial energy stores, but they differ significantly in structure and function. Carbohydrates, such as glucose, are typically readily available for immediate energy, whereas lipids are better suited for long-term energy storage. Structurally, carbohydrates are composed of carbon, hydrogen, and oxygen, often following the formula (C_x(H_2O)_y). They range from simple sugars (monosaccharides) to complex polysaccharides like starch and cellulose. Lipids, however, are a diverse group of compounds including fats, oils, and certain hormones. They are largely hydrophobic, and some are amphipathic, possessing both hydrophilic and hydrophobic regions. Functionally, carbohydrates are key energy sources and structural components in organisms. Lipids function as energy storage, structural components of cell membranes, and as chemical messengers.

How do nucleic acids like DNA and RNA store and transmit genetic information?

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are essential molecules that manage the hereditary traits of cells and organisms. The sequence of bases in DNA acts as a code for storing genetic information. DNA uses this code to synthesize ribonucleic acid (RNA) , which carries the genetic code to the sites of protein synthesis. Messenger RNA (mRNA) carries codes from DNA to ribosomes for protein synthesis. Transfer RNA (tRNA) carries amino acids to ribosomes, where they link to form proteins based on mRNA's order. The order of tRNA molecules determines the amino acid sequence of a protein.

Biomolecule

Introduction References & Edit History Quick Facts & Related Topics

Images & Videos

Diagram of a DNA polynucleotide chain showing linked deoxyribose sugars, phosphate groups, and nitrogenous bases (adenine, guanine, cytosine, thymine), with an inset comparing ribose and uracil in RNA.

Detailed diagram of a plasma membrane's lipid bilayer showing two layers of phospholipid molecules with hydrophilic heads facing outward and hydrophobic tails inward, embedded cholesterol, integral (intrinsic) proteins spanning the membrane, peripheral (extrinsic) proteins attached to the surface, and sugar side chains extending from the outer face.

Diagram showing the step-by-step process of DNA packaging: DNA wraps around histone proteins to form nucleosomes, which condense into chromatin fibers that further coil and fold to create a compact chromosome structure.

Large biological molecules: Carbs, lipids, proteins, and nucleic acids

Quick Facts

Also called:: biological molecule

Key People:: Jacques Dubochet

Related Topics:: Protein; Lipid; Nucleic acid; Carbohydrate; Steroid

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Biomolecule

biology

Also known as: biological molecule

Written by

Kara Rogers

Fact-checked by

Britannica Editors

Last updated

Nov. 12, 2026 •History

Top Questions

What is a biomolecule?
Biomolecules are substances produced by cells and living organisms, exhibiting diverse sizes, structures, and functions. The primary types include carbohydrates, lipids, nucleic acids, and proteins.
- Nucleic acids (DNA and RNA) uniquely store an organism’s genetic code, determining the amino acid sequence of proteins.
- Proteins are structural components, transporters, enzymes, catalysts, antibodies, and hormones.
- Carbohydrates are key energy sources and structural components, built from sugar units.
- Lipids serve as stored energy, chemical messengers, and membrane components, separating cells and creating organelles.
All biomolecules share a structure-function relationship influenced by their environment.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What are the main types of biomolecules?
Biomolecules are substances produced by cells and living organisms, displaying a vast array of sizes, structures, and functions. The four main types are carbohydrates, lipids, nucleic acids, and proteins.
- Carbohydrates are key energy sources and structural components, built from sugar units.
- Lipids serve as stored energy, chemical messengers, and form membranes.
- Nucleic acids (DNA and RNA) uniquely store an organism’s genetic code and direct protein synthesis.
- Proteins are major structural elements, transporters, enzymes, antibodies, and hormones.
6 Britannica Sources
1. nucleic acid
2. polymer
3. protein
4. carbohydrate
5. lipid
6. biomolecule
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why are biomolecules important for living things?
Biomolecules are crucial for living organisms due to their vast array of functions. The four major types are carbohydrates, lipids, nucleic acids, and proteins.
- Carbohydrates are essential energy sources and structural components.
- Lipids provide stored energy, act as chemical messengers, and form membranes that separate cells.
- Nucleic acids (DNA and RNA) uniquely store an organism’s genetic code, determining the amino acid sequence of proteins.
- Proteins are major structural elements, transport nutrients, catalyze reactions, form antibodies and hormones, and influence gene activity.
  The conversion of carbon dioxide into carbohydrates by green plants, using light energy from the Sun, is an essential process that has permitted the evolution of life as it now exists.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What roles do proteins play as biomolecules?
Proteins are complex biomolecules essential to all living organisms and hold immense nutritional value as they directly participate in the chemical processes that sustain life.

Diverse roles of proteins:
- Catalysis Almost all enzymes are proteins that catalyze metabolic reactions, enabling organisms to create chemical substances that are necessary for life.
- Structural Support Structural proteins maintain and protect the structure of the animal body.
- Hormones Some proteins act as hormones and have important regulatory functions.
- Transport Hemoglobin, a respiratory protein, transports oxygen in the blood. Membrane transporters facilitate the movement of molecules across the cell membrane.
- Defense Antibodies are proteins that protect animals from disease.
- Gene Expression Proteins control the activity of genes.
- Cellular Communication Proteins present on cell surfaces enable cells to recognize and adhere to the extracellular matrix and one another.
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How do carbohydrates and lipids differ in structure and function?
Carbohydrates and lipids both serve as crucial energy stores, but they differ significantly in structure and function. Carbohydrates, such as glucose, are typically readily available for immediate energy, whereas lipids are better suited for long-term energy storage.

Structurally, carbohydrates are composed of carbon, hydrogen, and oxygen, often following the formula (C_x(H_2O)_y). They range from simple sugars (monosaccharides) to complex polysaccharides like starch and cellulose. Lipids, however, are a diverse group of compounds including fats, oils, and certain hormones. They are largely hydrophobic, and some are amphipathic, possessing both hydrophilic and hydrophobic regions.

Functionally, carbohydrates are key energy sources and structural components in organisms. Lipids function as energy storage, structural components of cell membranes, and as chemical messengers.
2 Britannica Sources
1. carbohydrate: Role in the biosphere
2. lipid
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How do nucleic acids like DNA and RNA store and transmit genetic information?
Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are essential molecules that manage the hereditary traits of cells and organisms. The sequence of bases in DNA acts as a code for storing genetic information. DNA uses this code to synthesize ribonucleic acid (RNA), which carries the genetic code to the sites of protein synthesis.

Messenger RNA (mRNA) carries codes from DNA to ribosomes for protein synthesis. Transfer RNA (tRNA) carries amino acids to ribosomes, where they link to form proteins based on mRNA's order. The order of tRNA molecules determines the amino acid sequence of a protein.
6 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Biomolecule, any of numerous substances that are produced by cells and living organisms. Biomolecules have a wide range of sizes and structures and perform a vast array of functions. The four major types of biomolecules are carbohydrates, lipids, nucleic acids, and proteins.

Among biomolecules, nucleic acids, namely DNA and RNA, have the unique function of storing an organism’s genetic code—the sequence of nucleotides that determines the amino acid sequence of proteins, which are of critical importance to life on Earth. There are 20 different amino acids that can occur within a protein; the order in which they occur plays a fundamental role in determining protein structure and function. Proteins themselves are major structural elements of cells. They also serve as transporters, moving nutrients and other molecules in and out of cells, and as enzymes and catalysts for the vast majority of chemical reactions that take place in living organisms. Proteins also form antibodies and hormones, and they influence gene activity.

Likewise, carbohydrates, which are made up primarily of molecules containing atoms of carbon, hydrogen, and oxygen, are essential energy sources and structural components of all life, and they are among the most abundant biomolecules on Earth. They are built from four types of sugar units—monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Lipids, another key biomolecule of living organisms, fulfill a variety of roles, including serving as a source of stored energy and acting as chemical messengers. They also form membranes, which separate cells from their environments and compartmentalize the cell interior, giving rise to organelles, such as the nucleus and the mitochondrion, in higher (more complex) organisms.

All biomolecules share in common a fundamental relationship between structure and function, which is influenced by factors such as the environment in which a given biomolecule occurs. Lipids, for example, are hydrophobic (“water-fearing”); in water, many spontaneously arrange themselves in such a way that the hydrophobic ends of the molecules are protected from the water, while the hydrophilic ends are exposed to the water. This arrangement gives rise to lipid bilayers, or two layers of phospholipid molecules, which form the membranes of cells and organelles. In another example, DNA, which is a very long molecule—in humans, the combined length of all the DNA molecules in a single cell stretched end to end would be about 1.8 metres (6 feet), whereas the cell nucleus is about 6 μm (6 10^-6 metre) in diameter—has a highly flexible helical structure that allows the molecule to become tightly coiled and looped. This structural feature plays a key role in enabling DNA to fit in the cell nucleus, where it carries out its function in coding genetic traits.

Kara Rogers

Biomolecule

Diverse roles of proteins:

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