How do monomers form polymers in biological molecules?

Monomers form polymers in biological molecules through a process called polymerisation, involving dehydration synthesis or condensation reactions.

Polymerisation is a chemical process that involves the combination of small molecules, known as monomers, to form a larger, more complex structure known as a polymer. This process is fundamental in biology, as it is responsible for the formation of many important biological macromolecules, such as proteins, nucleic acids, and polysaccharides.

The process of polymerisation typically involves a type of reaction known as a dehydration synthesis or condensation reaction. In a dehydration synthesis reaction, two monomers are joined together with the removal of a water molecule. This is achieved by the donation of a hydrogen atom from one monomer and a hydroxyl group from the other, which together form a water molecule. This leaves a new covalent bond between the two monomers, effectively linking them together to form a dimer. This process can be repeated multiple times, with new monomers being added to the chain to form a polymer.

For instance, in the formation of a protein, the monomers are amino acids. Each amino acid has an amino group (-NH2) and a carboxyl group (-COOH). During polymerisation, the amino group of one amino acid reacts with the carboxyl group of another, releasing a water molecule and forming a peptide bond. This process is repeated to form a polypeptide chain, which can then fold and coil to form a functional protein.

Similarly, in the formation of nucleic acids like DNA and RNA, the monomers are nucleotides. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. The phosphate group of one nucleotide reacts with the hydroxyl group on the sugar of another nucleotide, releasing a water molecule and forming a phosphodiester bond. This links the nucleotides together to form a polynucleotide chain, which is the backbone of a nucleic acid molecule.

In summary, the process of polymerisation, involving dehydration synthesis or condensation reactions, is crucial in the formation of biological polymers from their respective monomers.