What Are Biological Molecules?

Enroll Biology XI Sindh Board Course

Biological molecules are the basic building blocks of living organisms. They promote various biochemical processes and vary in their structure and size.

The major biomolecules are carbohydrates, lipids, proteins and nucleic acids. These four groups of biomolecules make up the majority of a cell’s mass and function to support and sustain life.


Carbohydrates are an important macronutrient for all living organisms. They are organic molecules composed of carbon (C), hydrogen (H) and oxygen (O).

Plants use sunlight to synthesize carbohydrates in photosynthesis, storing the absorbed energy in plant cells for later use as energy. Animals also use carbohydrates as fuel in metabolism.

Biologically important carbohydrates can be classified as simple sugars, monosaccharides, disaccharides and polysaccharides. Skill 25.1 defines a simple sugar as one that contains 3 to 7 carbon atoms and a formula of (CH2 O)n, where n is a number from 3 to 7.

In addition, some simple sugars can be formed into cyclic monosaccharides with different stereoisomers. The OH group on the first carbon atom of a cyclic monosaccharide may be pushed upward or downward, giving rise to two stereoisomers known as alpha and beta forms.


Lipids are an important class of organic molecules that are insoluble in water. They include fats, oils, waxes and steroid hormones.

Lipids provide a number of important biological functions, including storing energy and forming structural components of cell membranes. They also serve as a source of signaling molecules within the body.

Some lipids are metabolised to yield large amounts of energy, while others are synthesised by the body to perform specific functions. Some lipids can cause problems, such as high blood cholesterol levels and heart disease.


Proteins are major structural components of cells, as well as transporters and other molecules needed for cellular function. They also help cells communicate with one another and send messages, act as hormones, and serve as enzymes.

The sequence of amino acids, the small organic molecules that make up proteins, determines their structure and function. There are 20 different amino acids commonly found in proteins; the order of their presence plays a critical role in determining a protein’s function.

Amino acids are linked together by peptide bonds that form when the carboxyl group of an amino acid is joined to the amino group of a neighboring amino acid. This condensation (joining) of multiple amino acids forms a long chain, or polypeptide.

The folding and intramolecular hydrogen bonding of the linear amino acid chain determines a protein’s unique three-dimensional shape. Stable folding patterns, known as alpha helices and beta sheets, occur as a result of this interaction. These regular, repeated patterns of folding constitute the secondary structure of a protein.

Nucleic Acids

Biological molecules are long chain-like molecules made up of repeating units or monomers (monomers are like beads on a bracelet). These biomolecules are composed of the elements carbon, hydrogen, oxygen, nitrogen and phosphorus.

Nucleic acids are biopolymers that contain repeated units of nucleotides. Each nucleotide is comprised of a phosphoric acid, a 5-carbon sugar (known as a pentose) and a nitrogenous base.

DNA is a nucleic acid that consists of a ribose sugar backbone and nitrogenous bases such as adenine, guanine, cytosine, and thymine.

RNA is another nucleic acid that consists of ribose sugar, nitrogenous bases such as adenine, and a phosphate group. Both DNA and RNA are used in biological molecules to store genetic information and act as messengers. ATP is a nucleic acid that combines adenine, ribose sugar and phosphate groups to generate energy for cellular processes. ATP is used by all living cells to carry out their functions. Its bonds are high energy bonds and provide energy for the cell to function properly.

What Are Biological Molecules?

Leave a Reply

Your email address will not be published. Required fields are marked *

Scroll to top