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Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.

Essential amino acids. There are nine amino acids that your body can’t make. They are called essential amino acids, meaning you must have them to live. They are found in foods like milk, eggs and meat and also a wide variety of plants. This is part of why you can’t survive on a diet of just corn chips for very long. Essential amino acids were actually discovered in an experiment testing something very similar to a corn chip diet. Scientists fed rats a diet that had only corn protein in it and observed the results. 21 is all it takes. The human body uses just 21 amino acids to make all the proteins it needs to function and grow. Because amino acids can be arranged in many different combinations, it's possible for your body to make thousands of different kinds of proteins from just the same 21 amino acids. Just like a Lego house is made of bricks, proteins are made up of lots of tiny building blocks. These building blocks are called amino acids. To build a protein, first the amino acids are connected into long chains. These chains of amino acid building blocks can then fold into all types of shapes. Some chains fold into spirals. Amino acids are organic compounds containing amine and carboxyl functional groups, along with a side chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known and can be classified in many ways. They can be classified according to the core structural functional groups' locations as alpha-, beta-, gamma- or delta- a In addition, cysteine, taurine, tyrosine, and arginine are considered semiessential amino-acids in children (though taurine is not technically an amino acid), because the metabolic pathways that synthesize these amino acids are not fully developed. show/hide words to know. 1  Amino acid: molecules that contain carbon, oxygen, hydrogen, and nitrogen. 2  Enantiomer: one of a pair of molecules that are mirror images of each other, but not identical... 3  Essential: required, or necessary. In 1902, Emil Fischer and Franz Hofmeister independently proposed that proteins are formed from many amino acids, whereby bonds are formed between the amino group of one amino acid with the carboxyl group of another, resulting in a linear structure that Fischer termed peptide. General structure Protein Parts. 1  Proteins are not the same as Lego building blocks, but proteins do have special shapes that can be used to build parts of the body. Johnson Righeira Lego portrait via Wikimedia. 2  21 Amino Acids (Source: Wikimedia) Click on the image to see a a larger version. show/hide words to know. 1  Amino acid: molecules that contain carbon, oxygen, hydrogen, and nitrogen. These are the building blocks of protein... 2  Enantiomer: one of a pair of molecules that are mirror images of each other, but not identical... more. 3  Essential: required, or necessary. Amino acid. Amino acids are organic compounds containing amine (-NH2) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, although other elements are found in the side chains of certain amino acids. About 500 amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways. Query: how many amino acids are considered by scientists to be essential?
Output:
There are nine amino acids that considered by scientists to be essential.