Organic Chemistry MCAT Practice Exam 2025 - Free MCAT Practice Questions and Study Guide

The correct choice highlights the presence of the two primary functional groups characteristic of amino acids: the amino group (-NH2) and the carboxylic acid group (-COOH).

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid is distinguished by its central carbon (alpha-carbon) bonded to four different groups: a hydrogen atom, an amino group, a carboxylic acid group, and a variable side chain known as the R group.

The amino group (-NH2) serves as a basic functional group that can accept protons, contributing to the amino acid's role in forming peptides and proteins. The carboxylic acid group (-COOH) donates protons, which is essential for the acid-base properties of amino acids.

Together, these two functional groups are fundamental to the structure and functionality of all amino acids, supporting their involvement in protein synthesis and various metabolic pathways. Other options do not represent the functional groups present in all amino acids and would not encompass their essential nature.