The answer is 22 amino acids are incorporated into natural proteins. While there are over 500 amino acids found in nature, only a select 22 are commonly used by living organisms to build the proteins essential for life.
Understanding Amino Acids
Amino acids are the fundamental building blocks of proteins. They are organic compounds distinguished by the presence of both amino (-NH2) and carboxylic acid (-COOH) functional groups. Here's a breakdown:
- Basic Structure: Each amino acid contains a central carbon atom (the alpha carbon), an amino group, a carboxyl group, a hydrogen atom, and a unique side chain (R group). It is the R group that distinguishes each amino acid.
- Diversity: Although over 500 different amino acids exist in nature, this diversity arises from the varying R groups.
- Protein Synthesis: The 22 alpha-amino acids are used by the ribosome, the cell's protein manufacturing machinery, to synthesize the wide array of proteins required for biological processes.
The 22 Standard Amino Acids
The crucial fact is that, of the vast number of amino acids, only 22 are incorporated into proteins. They are:
| Amino Acid Category | Number |
|---|---|
| Standard Amino Acids | 20 |
| Selenocysteine | 1 |
| Pyrrolysine | 1 |
Why Only 22?
The specificity in protein synthesis comes down to the genetic code. This code, which is carried by mRNA, uses specific triplets of bases (codons) to determine which of these 22 amino acids should be added during protein synthesis. This mechanism is incredibly precise and contributes to the structure and function of proteins.
Key Points
- Over 500 Amino Acids: Nature has produced more than 500 kinds of amino acids.
- 22 Used in Proteins: Only 22 alpha-amino acids are actually used by cells to build proteins.
- Functionality: The precise sequence of these 22 amino acids in a protein chain determines its overall three-dimensional shape and functionality.
- Importance: Proteins are critical for cell structure, enzymes, immune system function and numerous other essential biological processes.
