A Level Biology Practice Exam

What forms a peptide bond?

1. Two monosaccharides

2. Two amino acids

3. Two nucleotides

4. Two fatty acids

The correct answer is: Two amino acids

A peptide bond is specifically formed between two amino acids. This type of bond occurs during a process called dehydration synthesis or condensation reaction, in which the carboxyl group of one amino acid reacts with the amino group of another, resulting in the release of a molecule of water and the formation of the covalent bond known as a peptide bond. This bond is fundamental to the structure of proteins, as it creates polypeptide chains that eventually fold into functional proteins. The other options refer to different types of biological macromolecules. For example, two monosaccharides form glycosidic bonds to create disaccharides; two nucleotides link through phosphodiester bonds to form nucleic acids like DNA and RNA; and two fatty acids can combine with glycerol to form triglycerides, but this involves ester bonds instead of peptide bonds. Each type of bond plays a specific role in the structure and function of various biomolecules.