A Level Biology Practice Exam

Polymers are indeed long-chain molecules formed by the chemical bonding of many smaller units, known as monomers. These monomers can be identical or different and are joined together through various types of chemical bonds, typically covalent bonds. This structure allows polymers to exhibit a diverse range of physical and chemical properties, influencing their function in biological systems.

The other options present different concepts that do not accurately describe polymers. Short-chain molecules composed of amino acids refer specifically to peptides, which are not classified as polymers in the same way that longer chains of repeating units are. Small molecules that cannot bond with others would describe monomers or perhaps simple non-reactive molecules, neither of which can be classified as polymers. Finally, suggesting that polymers are only carbohydrate-based molecules excludes the vast array of polymers that exist, including proteins (made of amino acids) and nucleic acids (made of nucleotides). Thus, the definition provided in the chosen answer captures the essence of what polymers are in a comprehensive manner.