Life as we know it on earth could not exist without three molecules: DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and protein. We rely on them for everything that happens in our body. Here’s a brief introduction:
DNA: Stores all the information on how to build your body. This information is what we call genes. All living things on the planet have DNA and it all contains the instructions for making that organism. These instructions are written in a code containing four letters (called bases). The order of these letters defines how a protein is made.
RNA: There are different types of RNA but the most common one is messenger RNA (mRNA) which takes the instructions coded by your DNA to the place in your cell where proteins are made. It uses a similar but slightly different four letter code.
Proteins: These are the work horses of your cell. They are responsible for all that goes on in your body including digestion, moving your muscles, building your bones and fighting infections. They are made of amino acids, 21 in total, that string together as instructed by the RNA.
Think of these molecules like this. DNA is like a book in a library about how to build a house. This book has many pages (genes) with instructions on different steps needed to build a house. Now this book is very old and so it is never allowed to leave the library. Instead, you are allowed to make copies of pages in the book and take them to wherever you are doing the work, these copies are the mRNA. Once you get to the worksite, you start building the foundation of your home using the instructions from this page, this foundation is like a protein.
These small molecules are the foundation of life.