Polar amino acids include serine, threonine, asparagine, glutamine, histidine and tyrosine. The hydrophobic amino acids include alanine, valine, leucine, isoleucine, proline, phenylalanine, tryptophane, cysteine and methionine.
http://www.proteinstructures.com/Structure/Structure/amino-acids.html
A series of codons in part of a messenger RNA (mRNA) molecule. Each codon consists of three nucleotides, usually corresponding to a single amino acid. The nucleotides are abbreviated with the letters A, U, G and C. This is mRNA, which uses U (uracil). DNA uses T (thymine) instead.
https://en.wikipedia.org/wiki/Genetic_code
For a while it was thought that there were only 20 amino acids, and many websites still reflect this today, but in fact, a couple of more rare aminos were discovered making a total of 22 amino acids.
http://aminoacidinformation.com/how-many-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).
http://www.innovateus.net/health/how-many-proteins-exist-human-body
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.
http://www.innovateus.net/health/how-many-proteins-exist-human-body
The portion of the genome that codes for a protein or an RNA is called a gene. Those genes that code for proteins are composed of tri-nucleotide units called codons, each coding for a single amino acid. Each nucleotide sub-unit consists of a phosphate, a deoxyribose sugar, and one of the four nitrogenous nucleobases.
https://en.wikipedia.org/wiki/Genetic_code
These are listed as: alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine. However, how many amino acids from one of the above groups are actually conditional or “ semi-essential ” amino acids? These are: arginine, cysteine, glycine, glutamine, proline, serine, tyrosine.
http://aminoacidinformation.com/how-many-amino-acids/
In certain proteins, non-standard amino acids are substituted for standard stop codons, depending on associated signal sequences in the messenger RNA. For example, UGA can code for selenocysteine and UAG can code for pyrrolysine. Selenocysteine is now viewed as the 21st amino acid, and pyrrolysine is viewed as the 22nd.
https://en.wikipedia.org/wiki/Genetic_code
How many amino acids are “ essential ” (meaning you must get them from food)? They are listed as: arginine, histidine, leucine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine.
http://aminoacidinformation.com/how-many-amino-acids/
There are 22 Amino Acids. These above are the 20 more well-known amino acids; however, just how many amino acids exist actually are counted as being over 200 in numbers, but the 22 proteinogenic amino acids are the ones that are commonly known.
http://aminoacidinformation.com/how-many-amino-acids/
there are how many different amino acids
There are 22 different types of amino acids.