Proteins are long molecular chains made from one of the 20 basic building blocks of life, Amino acids. The amino acids in a polymer are connected together by the peptide bonds between the carboxyl and amino groups of adjacent amino acids. The carboxyl group contains 1 carbon and 1 hydrogen atom and 2 oxygen atoms (CO-OH). The amine group contains 1 nitrogen atom attached to 2 hydrogen atoms (H-N-H). Proteins are also known as Poly peptides. The word protein came from the greek word ”Prota”, meaning “of primary importance”. This name was introduced by Jons Jakob Berzelius in the year 1838.
When we consume foods which has proteins, the digestive system breaks it down into amino acids which enter into the pool of amino acids in our blood stream. Each cell then gathers the needed amino acids from the blood stream to create required proteins. Proteins perform most of the work in the body including building the structure, regulating the functions of body’s organs and tissues. So, eating a diet rich of protein is very important for our health. Without dietary protein, growth and other essential bodily functions will not take place properly. Proteins are also used for the transport of nutrients and oxygen throughout the body. Proteins provide collagen to connective tissues of skin, hair and nails. Proteins are also an integral part of our hormones and enzymes, and they to resist infection and diseases.
It is not necessary to include all the essential amino acids in every meal. If we eat variety of proteins throughout the day, the body will absorb take what it needs.
Scientists have tried to answer that question, but it a difficult one to accurately answer, as proteins are complex and dynamic molecules. All else being equal a small change in the one of the underlying amino acids can render the protein inactive. So the question becomes, should all those inactive proteins be counted as well. And what about proteins that have exact similar properties but different amino acids combinations. For instance, let's take hemoglobin. It generally has 146 amino acids, but not all them are essential for the protein to be functional. So, if we a ask a question as to how many different amino acids are necessary for the protein to be known as the "hemoglobin" protein, then the answer depends on many things. Whenever changes in amino acid affects the physical structure of protein molecule, the affected protein becomes inactive. Then it no longer is the same protein. When the amino acids with similar chemical properties replace each other in a protein, then it will not affect the protein structure, and hence the protein remains the same albeit with a different amino acids composition. Also, some proteins are just a comfort for the cells and some proteins are very essential. Given that broad context under which proteins are classified, the total number of proteins in human body is estimated to be around 50,000.
Since every protein can be broken down by another protein, different type of proteins produced by a single cell organism ranges from two to four thousand. The common bacteria E-coli is predicted to have a total of 5,000 organic compound of which 3,000 are proteins. It is also estimated that human body has the ability to generate 2 million different types of proteins, coded by only 20,000-25,000 of our genes. The sum of proteins in biological organisms exceeds 10 million, but nobody has a clear picture of this. The field of research that focuses on proteins and catalogs all proteins in human body is known as Proteomics. The next step after completing the Human Genome project may be the Human Proteome project. The Human Proteome organization is being formed to achieve the goal of identifying and cataloging all the different proteins in the human body.