Any living matter is basically composed of six elements (Carbon, oxygen, Nitrogen, Sulphur, Phosphorous, and Hydrogen). In humans, they form about 90% of the dry weight.

Biomolecules are those which are produced by living organisms and are very important for their day-to-day activities. They are structurally dependent and lose their function on disruption. They are usually composed of simple subunits called monomers, which combine chemically to form large and complex polymers.

Carbon, Hydrogen, and Oxygen are the common elements that make all of the biomolecules.

Biomolecules are broadly classified into four categories, carbohydrates, proteins, lipids, and nucleic acids. To solve biology assignments, you need to know these topics.

1. Carbohydrates

These are basically made up of carbon, hydrogen, and oxygen.

Carbohydrates are made up of building blocks like sugars, fiber, and starches. Sugars are usually found in vegetables, milk, and fruits, whereas fiber and starches are usually found in legumes and grains.

These sugars are named saccharides and are classified into monosaccharides, disaccharides, and polysaccharides based on the presence of one or two or more sugar residues. These sugars are the best energy reservoirs for breaking down into simple sugars called glucose.


– Monosaccharides: Glucose, fructose, and Galactose.

– Polysaccharides: Sucrose (made up of glucose and fructose saccharides).

Functions of Carbohydrates:

– Carbohydrates are the best energy reservoirs

–  They are the form precursors for most organic compounds.

– They form the vital part of the backbone of DNA & RNA.

– Glycoproteins & glycolipids, form the major part of the cell membrane and aid in cellular functions like growth and adhesion.

– Plants store the sugars in the form of starch, whereas animals store them in the form of glycogen.

2. Proteins

These are the predominantly found biomolecules in the living system. They are found in each and every cell and form 50% of the dry weight. They form the structural and physiological basis of life.

Proteins are made up of aminoacids. Hundreds of aminoacids exist in nature but only 20 aminoacids are involved in the building up of the proteins.  Each aminoacid contains a aminogroup at one end and a carboxy group at another end, with a central carbon atom. The side chain which is variable like hydrophobic, hydrophilic, charged, and neutral, is what makes the different proteins differ from each other.

Soya products and animal sources (meat, poultry, fish, and eggs) are rich in proteins. Amino acids the building blocks of proteins are basically linked by peptide bonds. Ribosomes, a cell organelle helps in forming these peptide bonds between these aminoacids and as such help in forming polypeptide chains, which on conformational changes develop into proteins. The proteins which are consumed are generally broken down into their amino acids, which are now feasible to enter the blood circulation. In due course of circulation, these amino acids are later used for building up proteins.  

Functions of Proteins

Proteins serve structurally and dynamically.

– They are solely responsible to give structure and strength to the body.

– They are found in elastin and collagen which form the hardest matrix in the body.

– They are also important in giving structure and flexibility to the epidermal tissues.

– They aid in regulating genetic functions.

– They help in muscle contraction via muscle proteins.

– Enzymes, clotting factors, hormones, and antibodies receptors are all made up of proteins and play a crucial role in the body’s metabolism.

– They help in communicating between and within the cells

– As such they are often credited as working horses of the cell.

3. Lipids:

These are the diverse group of biomolecules that are hydrophobic in nature and form the structural components of the cell membranes and they are similar to carbohydrates in terms of storage.

They are hydrophobic as such do not dissolve in water. They are of the great demand for the body as they form the chief storage form of energy. Plant lipids are generally liquids (eg., olive oil) whereas animal lipids are solids (fats).  The building blocks of Fats are usually made up of fatty acids and glycerol. Fattyacids are usually used for storing energy. These link together with the glycerol subunits to form the diglycerides and triglycerides.

Examples of fattyacids are lauric, oleic, palmitic, stearic, linoleic, and linolenic acids.

Functions of Lipids:

– They are the form of concentrated energy reserves for the body.

– Lipids are the main components in the structure of cell membranes.

– These aid in regulating membrane permeability.  

– They are a rich source of fat-soluble vitamins like A, D, E, and K.

– These act as metabolic regulators via steroids and prostaglandins).

4. Nucleic Acids

These are the complex group of biomolecules, and form the main and essential component of life.

These are the most important macromolecules involved in encoding, transmitting, and gene expression. Genetic information is usually encrypted in the form of nucleic acids and is transmitted to the next generations. They, also help in protein synthesis.

They are made up of simple subunits called nucleotides. These subunits are basically composed of three components like carbon sugar, a phosphate group, and a base. Based on the sugar moiety present they are further classified as DNA and RNA. In the case of DNA, the sugar moiety is the deoxyribose sugar, and in the case of RNA, it is ribose sugar.

DNA in turn is composed of four nucleotides called guanine (G), adenine(A), thymine(T), and cytosine(C). In the case of RNA, uracil (U) replaces thymine. Two DNA strands are joined together by weak hydrogen bonds between the bases. RNA is usually a single strand and does not involve in the double helix formation.

Functions of Nucleic Acids:

– They aid in storing and transferring genetic information. 

– They help in protein synthesis. 

– They regulate the cell cycle and control RNA synthesis. 

– m-RNA helps in transferring the genetic message from RNA.

– r-RNA which are mostly seen in the ribosomes give stability to m-RNA.

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