Amino acid synthesis refers to the process by which living organisms produce amino acids, the building blocks of proteins. This process can occur through two main pathways: the transamination pathway, where amino groups are transferred between molecules, and the de novo synthesis pathway, where simple organic compounds are converted into amino acids. In humans and many other organisms, some amino acids are classified as essential, meaning they must be obtained from the diet, while others are non-essential and can be synthesized internally. Key enzymes and metabolic pathways, such as those involving glycolysis and the Krebs cycle, play crucial roles in this synthesis.