In biochemistry, proteins are macromolecules built by linking together many copies of which type of small monomer units?

Introduction / Context:
Biological macromolecules such as proteins, nucleic acids, and polysaccharides are built from repeating smaller units called monomers. Each class of macromolecule has its own characteristic type of monomer. Proteins play many roles in living organisms, including acting as enzymes, structural components, and signalling molecules. To understand how proteins are formed and how they function, it is essential to know the basic monomer units from which they are constructed. This question asks you to identify those monomers.

Given Data / Assumptions:

• Proteins are large biological macromolecules composed of long chains.
• These chains are sometimes called polypeptides.
• The options include amino acids, nucleotides, disaccharides, chaperones, and fatty acids.
• We assume a basic understanding of the major biomolecule classes: proteins, nucleic acids, carbohydrates, and lipids.

Concept / Approach:
Proteins are polymers whose repeating monomer units are amino acids. Each amino acid has an amino group, a carboxyl group, a hydrogen atom, and a characteristic side chain attached to a central carbon. In cells, amino acids are linked together by peptide bonds during protein synthesis on ribosomes. Nucleotides are monomers of nucleic acids like DNA and RNA, disaccharides are small carbohydrate units, chaperones are special proteins that help other proteins fold, and fatty acids are components of lipids. Only amino acids directly serve as the monomer building blocks of proteins.

Step-by-Step Solution:
Step 1: Recall that proteins are also called polypeptides, indicating they consist of many peptide bonds linking small units. Step 2: Recognise that each peptide bond connects the amino group of one amino acid to the carboxyl group of another amino acid. Step 3: Understand that a protein primary structure is defined by the linear sequence of amino acids in its chain. Step 4: Compare this with nucleic acids, where nucleotides are joined to form DNA and RNA, and with carbohydrates, where monosaccharides form polysaccharides. Step 5: Conclude that the monomers specifically used to build proteins are amino acids, not nucleotides, disaccharides, chaperones, or fatty acids.

Verification / Alternative check:
Standard biology textbooks state that there are about 20 common amino acids used in protein synthesis. These amino acids are encoded by the genetic code and joined in various sequences to create the vast diversity of proteins in living organisms. Experimental methods like protein sequencing and mass spectrometry identify proteins by their amino acid sequences. Nucleotides are clearly identified as monomers of DNA and RNA, while disaccharides such as sucrose and lactose are small carbohydrate units, not protein building blocks. This consistent evidence supports amino acids as the correct answer.

Why Other Options Are Wrong:
Nucleotides are monomers of nucleic acids, not proteins. Disaccharides are carbohydrates made of two monosaccharide units and play roles in energy metabolism, not in forming protein chains. Chaperones are proteins that assist in folding other proteins but are not monomer units; they are themselves built from amino acids. Fatty acids are components of lipids such as triglycerides and phospholipids and do not directly form protein backbones. Therefore, none of these alternatives are the monomer units that make up proteins.

Common Pitfalls:
Students sometimes mix up different classes of biomolecules, especially when they are introduced together in a single chapter. A typical confusion is between nucleotides and amino acids because both have nitrogen containing groups. Another pitfall is to see the word chaperone and think it might be a small unit, when it actually refers to whole proteins. To avoid such mistakes, remember a simple mapping: amino acids for proteins, nucleotides for nucleic acids, monosaccharides for carbohydrates, and fatty acids plus glycerol for many lipids.

Final Answer:
Proteins are macromolecules built by linking together many amino acids as their monomer units.