The building blocks of proteins are amino acids. Proteins are composed of long chains of amino acids linked by peptide bonds, forming polypeptide chains
Key points about amino acids as protein building blocks:
- Each amino acid has a central alpha (α) carbon bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom
- A distinctive side chain called the R group, which varies among amino acids and determines their properties
- There are 20 standard amino acids that make up proteins in humans, with some sources recognizing up to 22 including selenocysteine and pyrrolysine (the latter not found in humans)
- Amino acids are classified nutritionally into:
- Essential amino acids (9 total, e.g., histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine) which must be obtained from the diet because the body cannot synthesize them.
- Non-essential amino acids which the body can produce.
- Semi-essential (conditional) amino acids which are synthesized by the body but may be required from the diet during stress or growth periods
- Amino acids differ in their side chains (R groups), which can be neutral, acidic, or basic, and influence protein structure and function
Summary
Proteins are polymers made from 20 amino acids linked in specific sequences. These amino acids serve as the fundamental building blocks of all proteins, determining their structure and biological activity
