Amino acids are a combination of hydrogen,carbon,oxygen and nitrogen (incidentaly thats why plants need nitrogen to grow properly).
Energy from respiration in the mitochondria is used to build up amino acids into proteins which is called protein synthesis which takes place in the ribosomes.Thee proteins we digest are broken into amino acids by the enzyme protease which is produced in the stomach, small intestine and pancreas.
We get amino acids from the combination of described make-up elements obtained from air, water and food.