Q.Explain the term, target molecules or drug targets as used in medicinal chemistry.

The human body carries out its biochemical processes through large biomolecules that perform crucial functions — chiefly proteins (as enzymes, which catalyse specific biochemical reactions, or as receptors, which receive and transmit chemical signals such as hormones and neurotransmitters), and also carbohydrates, lipids and nucleic acids in some cases.

A drug is designed to bind to one such macromolecule — its target molecule or drug target — and modulate its activity:

• as an enzyme inhibitor, it can block or slow the enzyme's catalytic action, or
• as a receptor agonist/antagonist, it can mimic or block the natural signalling molecule at that receptor.

Because the target performs an essential role in a specific pathway or disease process, binding a drug to it selectively alters that pathway, producing the desired biological/therapeutic effect while (ideally) leaving other pathways unaffected.

Recall that drugs act by binding large biomolecules (proteins mainly). Explain the two chief protein target types — enzymes and receptors — and how binding to each produces a therapeutic effect.

• Describing 'target molecules' as small molecules rather than the large biomolecule the drug acts on.
• Failing to name that they are typically proteins (enzymes/receptors).