A Level Biology Practice Exam

What is meant by 'synthesis' in biological terms?

1. Breaking down large molecules into smaller ones

2. Combining small molecules to form larger ones

3. Transporting molecules across cell membranes

4. Removing excess molecules from a system

The correct answer is: Combining small molecules to form larger ones

In biological terms, 'synthesis' refers specifically to the process of combining smaller molecules to form larger ones. This is crucial for a variety of biological functions, such as the formation of macromolecules like proteins, nucleic acids, and polysaccharides, which are essential for life. The synthesis process often involves chemical reactions, where simpler molecules (monomers) undergo dehydration reactions or condensation to form more complex structures (polymers). For example, during protein synthesis, individual amino acids are linked together by peptide bonds to form polypeptide chains, which then fold into functional proteins. Similarly, during photosynthesis, simple carbon dioxide and water molecules are combined using energy from sunlight to produce glucose, a more complex molecule. Understanding synthesis is fundamental in biology, as it underpins metabolic pathways and the building blocks of cellular structures and functions.