How Many Proteins Exist?
It is estimated that the human body may contain over two million proteins, coded for by only 20,000 - 25,000 genes. The total number found in terran biological organisms is likely to exceed ten million, but nobody knows for sure. Data is available on just over a million of them, taken mainly from information found in the over 100 genomes that have been fully sequenced.
The field that analyzes proteins in general and aims to exhaustively characterize all of those in the human body is called proteomics. Many see the next logical step after the completion of the Human Genome Project to be the initiation of a Human Proteome Project. The Human Proteome Organization was founded to pursue this goal.
Proteins are long molecular chains made from the 20 basic building blocks of life, amino acids. The longest known one, titin, also known as connectin, contains 26,926 amino acids. Titin is found in muscle and contributes to its passive stiffness. Because the 20 amino acids can be connected up in arbitrary sequences, the total space of possible proteins is exponential, with a value of approximately 2050,000 — a tremendous number. Within this space there may be cures for every disease or ailment, but locating them in such a vast number is a profound computational and theoretical challenge.
The word protein comes from the Greek prota, meaning "of primary importance." This is a suitable name, as their central importance in the human body can not be overestimated. All biological organisms can be seen fundamentally as protein structures filled with water and sometimes supported by mineralized tissues called bone. For almost every one, there is another that can break it down. They sometimes coalesce into mutually cooperative units called complexes, which perform useful biological functions. Every section of useful genetic information, found in DNA and some RNA, codes for a corresponding protein that goes on to fulfill a useful biological role.
How many are made a day?
I can't believe that there are millions of proteins! And what's even more amazing is that each of these proteins have its own function. So no two proteins do the same exact thing! I can't even completely grasp what that means!
If what @burcidi said is true, that there are billions of proteins in one single cell, can you imagine how many proteins are at work all the time for our organs, our entire body to function?
My class notes say that there are at least one hundred trillion cells in the body. So one hundred trillion times ten billion gives us the total number of proteins in our body. The result comes out to be: one times ten to the power of twenty four. I'm not even sure what that means! I guess ten, followed by twenty four zeroes?! That's a lot of protein!
@anon26424-- That looks like a straight-forward, easy question but it isn't. Scientists actually don't know the exact number or variety of proteins in a cell. And I'm sure it ranges from one cell to the next. But it is estimated that there are about ten billion proteins in one human cell.
The reason your question is tricky is because you asked "different proteins." These ten billion proteins are definitely of different varieties, thousands of them. But like I said, we don't know the exact number.
If you need this information for homework, I think it's safe to say that there are approximately ten billion proteins of at least ten thousand types in one human cell.
@mankygoat, @ElizaBennett-- I don't know the exact answer, but my instructor was talking about a chemist's book in class recently. This chemist, I think his name was deDuve, estimated that there were around three million combinations of proteins (different proteins) on earth.
He calculated this based on the information that each protein is made up of anywhere from less than one hundred amino acids to more than one thousand. He assumed that a typical protein would have around two hundred amino acids. And since there are twenty different amino acids, the possible combinations would be a calculation of twenty to the power of two hundred.
So I think @ElizaBennett is right. To calculate the space of proteins, you can estimate the length of a typical protein and then calculate the possible combinations.
@anon137829 - What does the RNA do if it doesn't create protein? I'm seeing pretty much what the article says, that each gene codes for one protein.
@mankygoat - I have the same question. I would assume that it involves taking the minimum and maximum practical lengths of a protein and seeing how many combinations could exist within that range made of up the 20 amino acids.
What is the total number of amino acids in the human body? Is there a way to calculate this? A rough estimate will do.
How was the total space of possible proteins calculated? And on what basis was this calculation performed?
How many different proteins are there in a typical human cell?
Post your comments