Final answer:
Ligands are molecules designed with shapes that are complementary to receptor binding sites, allowing them to bind specifically to those receptors. This concept is key to enzyme specificity and drug development where molecules like enantiomers play a crucial role due to their 3D shape.
Step-by-step explanation:
Molecules with a shape complementary to the binding site of a receptor are generally known as ligands. Their unique shape allows them to bind specifically to receptors, enabling crucial biological processes. In the context of enzymes, these molecules are referred to as substrates, and the phenomenon where they bind only to active sites with compatible shape and charge is known as enzyme specificity.
Ion channel-linked receptors also demonstrate this specificity; they bind a ligand to open a channel allowing ions to pass through. In terms of drug design, understanding the three-dimensional shape of ligand binding sites on nuclear receptors is crucial for developing new drugs to regulate gene expression. This has been extended through the usage of positive and negative allosteric modulators (PAMs and NAMs), which can alter the shape of the binding site to modulate receptor activity.
Enantiomers are a perfect illustration of this concept. They are mirror-image molecules that, despite their similarity, have very different interactions with biological molecules due to the specificity of molecular interactions governed by their three-dimensional shapes. Consequently, only certain enantiomers are active in the body, designing drugs with the correct 3D structure is critical.