The 4 groups of organic compounds found in the living organisms - carbohydrates, lipids, proteins, and Nucleic acids - are also known as macromolecules. These macromolecules are made up of smaller molecules, generally known as monomers, which polymerize to yield such large molecules (generally polymeric in nature).
Carbohydrates are made of monosaccharides and are also known as polysaccharides. Carbohydrates consist of carbon, hydrogen and oxygen. Some examples of monosaccharides are glucose and sucrose. These monosaccharides are also known as sugars. Carbohydrates are necessary for storage of energy and as components of important molecules (such as RNA), apart from other roles in living organisms. The commonly known carbohydrates in our food are starch and sugars.
Lipids are an integral component of cells and form the cellular membrane (as phospholipids). They are also useful as fats (energy storage in living beings), vitamins, etc. These macromolecules are amphiphilic in nature, that is, they have both a hydrophilic and a hydrophobic end. This unique nature allows lipids to interact with both hydrophilic and hydrophobic molecules.
Proteins are made up of amino acids and are necessary for cell signaling, adhesion, enzyme-catalyzed reactions, replication of genetic material, etc. Unlike carbohydrates and lipids, proteins do not store energy, but carry out other important tasks in a living organism. Proteins contain carbon, nitrogen, hydrogen and oxygen. Various amino acids connect with each other through peptide bonds and the sequence of amino acids results in different proteins.
Nucleic acids are essential components of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) in living organisms and are responsible for genetic information's expression. The monomer of a nucleic acid is known as a nucleotide, which is a combination of sugar and a phosphate group with a nitrogenous base. These are among the largest macromolecules and may contain millions of bases.
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