Final answer:
The amino acids that are not produced by the human body and must be obtained externally via the diet are referred to as essential amino acids. There are nine of these, and they play a crucial role in protein synthesis in the body.
Step-by-step explanation:
Amino acids that are not manufactured by the human body and must be obtained through diet or other external sources are known as essential amino acids. The body can synthesize many amino acids from components of other molecules, but there are nine essential amino acids that cannot be synthesized and have to be consumed in the diet. These include isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, histidine, and valine.
These essential amino acids are needed for protein construction in the human body. The body breaks down proteins in food during digestion and absorbs the resulting amino acids. These amino acids then enter the body's amino acid pool, where they are used to assemble new proteins. If a particular essential amino acid is not present in sufficient amounts in this pool, human body cells cannot properly synthesize proteins that require it.
Learn more about Essential Amino Acids