The 20 Amino Acids

amino acids

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3 Responses to The 20 Amino Acids

  1. Phil Krause says:

    Amino Acids sound boring, what the hell are they? They form naturally, on the beach, on asteroids and on other planets; even on space dust or in Stanley Millers flask.

    Amino acids are in fact one of the most interesting substances in life. They can link together end to end to form chains. When two amino acids link together, an oxygen and a hydrogen from one end and a hydrogen from the other are ejected as water and the two amino acids are linked together by the resulting peptide bond. As water is released we call this a condensation reaction. When several amino acids are joined in this way, it is called a polypeptide because it has many peptide links or bonds. When the chain gets a little longer they are called cytokines and hormones which animals use for communication circulating within the blood or cell. When they get even longer, they are called proteins which all life uses to build bodies, structures and the enzymes which accelerate reactions. For example, in the presence of water, these peptide bonds will break down, inserting the water back on the ends of the amino acids and also producing energy. However, this process is very slow taking about 1000 years on average. Certain enzymes produced in this way can make this reaction happen in milliseconds. This is exactly how all life works.

    All life, produces twenty stretches of DNA that translate to twenty stretches of RNA that attract the twenty amino acids shown in this picture that are dissolved inside our cells. Each one of the twenty, similar but slightly different stretches of RNA attracting only one of the amino acids in the picture which joins onto the RNA stretch. We call these combinations tRNA for transfer RNA. These are joined together forming proteins in a remarkable piece of cellular machinery called Ribosomes.

    Simpler life like bacteria can make all these twenty amino acids with their own metabolism. Life that is further up the evolutionary tree can usually no longer make all of them. Insects for example can only make about half of them. So insects must eat things that contain the other ten amino acids. Their bodies break down these proteins that they have eaten into their constituent amino acids that they can combine to make the twenty tRNA molecules which go on to link together to make their own proteins within ribosomes. We can only make ten as well so we must also eat things that contain the others. We call the ten amino acids that we cannot make and must eat, “essential amino acids”. Most life contains all the amino acids but in varying quantities. Over time, because we always eat things that contain most of these amino acids we have lost the ability to make all of them. Why continue to make them if you always eat them?

    Although all life, bacteria, plants, fungi and animals all use these same twenty amino acids to make proteins, we all make slightly different proteins. All animals make a protein called collagen which is a connective tissue that glues our cells together and also makes our ligaments, tendons and bones etc. About 35% of the protein we make is collagen, it makes our main body structure and glue. However, as well as the amino acids shown in the picture that all life codes for, we can make a few others from the twenty. Collagen, for example requires two others. One made from proline modified to produce hydroxyproline and the other from lysine to produce hydroxylysine. These amino acids are modified with the help of Vitamin C (a cofactor) which we must eat in order to make collagen. If we don’t eat any vitamin C at all, like the early sailors, we get scurvy and eventually die. So we also need to eat our vitamins to, which is another story.

    • Deskarati says:

      Thanks for that Phil, very interesting.
      Here’s a Deskarati Fun Fact – L-Cysteine – an amino acid used to prolong shelf-life in products such as commercial bread – can be found in duck and chicken feathers and cow horns, but most that’s used in food comes from human hair. It has been reported that most of the hair used to make L-Cysteine comes from China, where it’s gathered from barbershops and hair salons.

  2. Naan Glozi says:

    There are around 500 known amino acids but only these 20 are used by life to make proteins.

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