Which two functional groups are always found in amino acids?
carboxyl and amino groups
ketone and methyl groups
amino and sulfhydryl groups
carbonyl and amino groups
hydroxyl and carboxyl groups
The correct answer and explanation is :
The correct answer is:
Carboxyl and amino groups
Amino acids, the building blocks of proteins, always contain two essential functional groups:
- Amino Group (-NH₂): This consists of a nitrogen atom bonded to two hydrogen atoms. The amino group is basic and can accept a proton, making amino acids capable of forming peptide bonds and participating in various biochemical reactions.
- Carboxyl Group (-COOH): This functional group contains a carbonyl (C=O) and a hydroxyl (-OH) component, making it acidic. It donates a proton in aqueous solutions, contributing to the acid-base properties of amino acids.
Explanation:
Amino acids serve as the fundamental units of proteins and are essential for various biological functions. Each amino acid consists of a central carbon atom (α-carbon) bonded to four groups: an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a variable side chain (R-group) that determines its specific properties.
The amino group acts as a proton acceptor, giving amino acids their basic properties, while the carboxyl group acts as a proton donor, giving them acidic properties. These functional groups allow amino acids to form peptide bonds during protein synthesis through a dehydration reaction, where the carboxyl group of one amino acid reacts with the amino group of another, releasing water.
Additionally, these groups contribute to the zwitterionic nature of amino acids at physiological pH. The amino group can be protonated to -NH₃⁺, and the carboxyl group can be deprotonated to -COO⁻, making amino acids amphoteric, meaning they can act as both acids and bases.
These properties are crucial in protein structure, enzymatic activity, and cellular function. The diversity of amino acids arises from the R-group, which varies among different amino acids, influencing their chemical behavior and role in proteins.
Amino group (-NH₂) on the left and the carboxyl group (-COOH) on the right, attached to the central α-carbon.