What type of biomolecule is characterized by having structural and functional diversity that includes amino and carboxylic acid groups?

The correct answer is proteins. Proteins are unique biomolecules composed of amino acids, which are the building blocks that feature both amino groups (-NH2) and carboxylic acid groups (-COOH). This structural characteristic allows proteins to possess a high degree of functional and structural diversity. Each of the 20 standard amino acids can vary in their side chains (R groups), which contribute to the overall properties and functions of the protein.

Proteins can serve various roles in biological systems, such as enzymes catalyzing biochemical reactions, structural components of cells and tissues, transport molecules, and signaling molecules. This diversity is fundamental to almost all cellular processes, as proteins can adopt complex three-dimensional shapes that are critical for their specific functions.

In contrast, carbohydrates primarily consist of sugar units and do not have the same diversity in terms of functional groups as proteins. Lipids are mainly hydrophobic molecules that do not feature amino and carboxylic acid groups in a manner akin to proteins. Nucleic acids, such as DNA and RNA, are composed of nucleotides and are primarily involved in genetic information storage and transmission, not possessing the amino and carboxylic acid functionalities characteristic of proteins.