True.
The basic building block or subunit of many biological molecules is often called a monomer. Monomers are small molecules that can be joined together through various chemical reactions to form larger, more complex molecules known as polymers. For example, amino acids are the monomers that are used to build proteins, while nucleotides are the monomers that are used to build nucleic acids like DNA and RNA. Carbohydrates like glucose and fructose are also considered monomers, as they can be joined together through dehydration synthesis reactions to form complex polysaccharides like starch and cellulose. Overall, monomers are an essential component of many biological molecules and play a critical role in the structure and function of living organisms.