Final answer:
There are 20 different amino acids that combine in sequences to form proteins with unique functions and structures. These proteins are critical to life and exhibit diverse properties and roles in biological systems.
Step-by-step explanation:
There are 20 different amino acids which can create an immense number of different proteins depending on how they are sequenced and arranged.
Each of these amino acids has a different R group (side chain), giving it unique chemical properties. Proteins formed from these amino acids can vary greatly in function and structure. The order in which amino acids are bonded changes the identity, properties, and function of the resulting polypeptide, much like how the sequence of letters forms different words. Despite there being only 20 amino acids, there are thousands of possible polypeptides that can be formed, and each of the naturally occurring proteins has its characteristic amino acid composition and sequence, resulting in a unique three-dimensional shape and specific function in the body.
Since scientists have determined the amino acid sequences and three-dimensional conformations of numerous proteins since the 1950s, they have obtained important clues about how proteins perform their functions. Similarly, the 20 amino acids are also classified as essential, non-essential, or conditionally essential, with essential amino acids being those that must be obtained from the diet as the human body cannot produce them.