AN ACID PRESENT IN PROTEINS IS

• A. lactic acid
• B. amino acid ✓
• C. propanoic acid
• D. palmitic acid
• E. stearic acid

The answer to the question is: B. amino acid

Amino acids are organic compounds that serve as the building blocks of proteins. They contain both an amino group (-NH2) and a carboxyl group (-COOH), making them amphoteric, meaning they can act as both acids and bases. The carboxyl group is what gives amino acids their acidic properties. When amino acids are linked together in a chain, they form a protein.

Amino acids are classified into two categories: essential and non-essential. Essential amino acids cannot be synthesized by the body and must be obtained through the diet, while non-essential amino acids can be synthesized by the body.

There are 20 standard amino acids that are commonly found in proteins. These include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

Amino acids play crucial roles in various physiological processes such as protein synthesis, neurotransmission, and metabolism. They are also involved in the structure and function of proteins and peptides.

In summary, the acid present in proteins is the amino acid due to its carboxyl group that imparts acidic properties to these organic compounds.