Complementary - GCSE Biology Definition

In GCSE Biology, the term "complementary" often refers to how certain shapes or structures fit together perfectly. It is like a lock and key system where one shape matches exactly with another. This idea is important when we talk about DNA, where the bases on the strands pair up in a specific way: adenine pairs with thymine, and cytosine pairs with guanine. These pairings are called complementary bases because they fit together perfectly, helping to hold the DNA structure together. Similarly, enzymes and their substrates are complementary, meaning the enzyme's active site is the right shape to bind to the substrate it works on.