Biomolecules - Types, Structure and Function

Biomolecules

Biomolecules are complex lifeless chemical substances that we get from living tissues. Biomolecules are the organic compounds that are essential for the maintenance of metabolic processes. Biomolecules not only build up the living cells but also help in their growth, development, and ability to reproduce.

JEE Main 2025: Chemistry Formula | Study Materials | High Scoring Topics | Preparation Guide

JEE Main 2025: Syllabus | Sample Papers | Mock Tests | PYQs | Study Plan 100 Days

NEET 2025: Syllabus | High Scoring Topics |  PYQs

This Story also Contains

1. Biomolecules
2. Function of biomolecules
3. Carbohydrates
4. Cyclic Structure of Carbohydrates
5. Proteins
6. Structure of Proteins
7. Amino acids
8. Nucleic acids
9. Structure of Nucleic acids

Function of biomolecules

Biomolecules are essential components of life and perform various functions such as:

• Carbohydrates are the source of energy they store energy and help in the recognition of cells
• Proteins help in the transportation of molecules across the cell membranes
• Lipids form the cellular membrane and provide insulation and protection to the organs.
• Nucleic acids store the genetic information and help in protein synthesis.

Examples of biomolecules

• Carbohydrates

Examples: Glucose, fructose, starch, cellulose, and sucrose.

• Proteins

Example: fibrous protein, globular proteins

• Nucleic acids

Example: DNA, RNA

Types of Biomolecules

There are four types of biomolecules:

• Carbohydrates
• Lipids
• Proteins
• Nucleic acids

Carbohydrates

Carbohydrates are the optically active polyhydroxy aldehydes or polyhydroxy ketones or substances that produce them on hydrolysis. Carbohydrates play a vital role in our daily life. They provide us the the three basic necessary things of life which are food (starch), clothing (cellulose), and shelter (cellulose).

Classification of Carbohydrates

Carbohydrates are also known as the saccharides. And classified into three categories

• Monosaccharide
• Oligosaccharides
• Polysaccharides

Monosaccharides

It cannot hydrolysis to the smaller molecules. Their general formula is (CH₂O)n where n= 3-7.

Oligosaccharides

These on hydrolyzed give 2-10 molecules of monosaccharides like Disaccharides, Trisaccharides, and Tetrasaccharides.

Polysaccharides

Carbohydrates in hydrolysis give a large number of monosaccharide units such as Starch, cellulose, and glycogen.

Reducing and Non-reducing Sugars
Those sugars that reduce Fehling's and Tollens's solutions are called reducing sugars and those that do not reduce these reagents are called non-reducing sugars. All the monosaccharides and disaccharides, except sucrose, are reducing sugars, whereas all the polysaccharides are called non-reducing carbohydrates.

Also Read:

• Classification Of Carbohydrates And Its Structure
• Properties Of Glucose
• Amino Acids
• Proteins
• Enzymes
• Vitamins

Cyclic Structure of Carbohydrates

The CHO group of glucose either reacts with the C-5 OH group or the C-4 OH group to give hemiacetalic linkage and forms stable six- and five-membered cyclic rings, respectively. If the CHO group reacts with the C-6 OH group, then a less stable seven-membered ring will form, or with C-3 OH, a four-membered ring will be formed, both are unstable.

Haworth representation: The cyclic structure of glucose was established by English chemist W.N. Haworth. The cyclic structure of glucose is depicted below.

Proteins

Proteins are the condensation polymer of the alpha-amino acids. They are present in almost all the living cells of plants and animals. In human beings, proteins are the main components of muscles, hairs, nails, tendons, arteries, and connective tissue. Each living cell is made up of thousands of different proteins.

Structure of Proteins

1) Primary Structure -Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence and it is this sequence of amino acids that is said to be the primary structure of that protein. Any change in this primary structure i.e., the sequence of amino acids creates a different protein.

2) Secondary Structure- Two types of secondary structure are alpha helix and beta plotted sheet structure which are held by hydrogen bonds.

3) Tertiary Structure -Tertiary structure is the interaction between protein molecules in a 3D manner which involves a disulfide bond, Hydrogen bond, and Ionic bond.

4) Quaternary Structure - Quaternary structure is an association of protein molecules in close arrangement.

The diagrammatic representation of all these structures are shown below:

Amino acids

Amino acids contain amino (-NH₂) and carboxyl (-COOH) as functional groups. Depending upon the relative positions of the -NH₂ group w.r.t -COOH group, the amino acids are classified as alpha, beta, gamma, delta, etc. amino acids. However, only alpha amino acid is obtained during the hydrolysis of protein. so that alpha amino acid is the building block of proteins

There are 20 amino acids in almost all proteins and these determine the properties of amino acids

Amino acids have amino(-NH₂) and carboxyl(-COOH) functional groups. Based on the relative position of the two functional groups in the alkyl chain, the amino acids are categorized as α, β,? δ and so on. On the hydrolysis of proteins, only α-amino acids are formed. Amino acids may also contain other functional groups.

• Amino acids which can be synthesized in our body are known as non-essential amino acids while those that can not be synthesized in our body are known as essential amino acids.
• They are usually colorless, water-soluble, high melting and crystalline solids.
• Except glycine, all other naturally occurring amino acids are optically active.
• Most naturally occurring amino acids have L-configuration.

NCERT Solutions Subject-wise:

• NCERT solutions for class 11 Physics.
• NCERT solutions for class 11 Chemistry.
• NCERT solutions for class 11 Mathematics.
• NCERT solutions for class 11 Biology.

Nucleic acids

Nucleic acid is the polymer present in the living system. Nucleic acids are also called polynucleotides because their repeating unit is a nucleotide. Nucleotides contain three parts i.e. a sugar molecule, a nitrogenous base, and a phosphoric acid.

Structure of Nucleic acids

The structure of nucleic acid contains:

• A pentose sugar: pentose sugar in DNA is called deoxyribose

pentose sugar in RNA is called ribose

• Nitrogenous base: 1) Purines

2) Pyridines

• Nucleoside and Nucleotide: Nucleosides contain pentose sugar and nitrogenous base

Nucleotides contain a sugar, base, and a phosphate group

A double helix consists of two strands that are antiparallel and complementary to each other. Two helixes are held together by hydrogen bonds.

NCERT Exemplar Solutions Subject-wise :

• NCERT exemplar solutions for class 11 Physics.
• NCERT exemplar solutions for class 11 Chemistry.
• NCERT exemplar solutions for class 11 Mathematics.
• NCERT exemplar solutions for class 11 Biology

Book for Biomolecules

For this chapter, first, you need to finish the important topics of biomolecules class 12 thoroughly from the class 12th NCERT book and then simultaneously solve the examples and questions given in the book.

Related Topics: