What is a drug target?
Your body works because of molecules called proteins. Many proteins have a small pocket on them. When a molecule sits in this pocket, the protein switches on or off.
A drug is a molecule that sits in such a pocket on purpose. The pocket is called the target. This is the lock-and-key idea: the shape of the drug must match the shape of the pocket. If it matches, the drug works. If not, nothing happens.
Natural drugs: help from plants and nature
For thousands of years, people tried plants, soil and moulds to treat illness. A medicine taken straight from nature is a natural drug. Examples: willow bark (pain), quinine from cinchona bark (malaria), and penicillin from a mould (infections).
Natural drugs often work, but they have limits. The amount in a plant changes from leaf to leaf. They can have side effects. Some are hard to find or too rare.
Synthetic drugs: improved in the lab
Chemists first find the active molecule, the one part that does the work. Then they can make it in a lab, or change a small part of it. A drug made or changed by people is a synthetic drug.
Why change it? To fit the pocket better, to cause fewer side effects, to be cheaper, or to last longer in the body. Aspirin is a lab-improved version of a plant molecule. Designing the best molecule on purpose is called drug design. Today computers help by testing thousands of shapes before any real chemistry starts.
Nanomedicines: tiny delivery trucks
A nanometre is one billionth of a metre. A nanomedicine uses particles of about 10 to 200 nanometres. These tiny capsules can be filled with a drug.
They help because they can carry the drug to the sick cells and leave healthy cells alone. This means a smaller dose and fewer side effects. Some mRNA vaccines also use tiny fat bubbles like this. Nanomedicines are new, and scientists still test them carefully for safety.
Try it
In the 3D: press each molecule button and count the knobs that match. Predict first: which one will work best? Then check.
At home: cut 3 paper keys with different bumps. Make a lock from card with 3 notches. Which key fits all 3? That is how a chemist thinks.
Key formulas and definitions
- Key terms: target = the pocket a drug fits into
- Natural drug = from plants, moulds or animals
- Synthetic drug = made or changed in a lab
- Nanomedicine = drug carried in a particle of 10 to 200 nm
- 1 nm = 10⁻⁹ m
Worked examples
1. A drug has knobs red, blue, grey. The pocket needs red, blue, yellow. How many match? Will it work well?
Red matches red and blue matches blue, so 2 of 3 match. Grey does not match yellow. It fits weakly, so it works poorly.
2. The chemist changes grey to yellow in the drug above. What is the fit now?
Now 3 of 3 knobs match the pocket. The improved synthetic drug fits well and works better.
3. A nanocapsule is 100 nm wide. How many metres is that?
1 nm = 10⁻⁹ m. So 100 nm = 100 × 10⁻⁹ m = 10⁻⁷ m.
Common mistakes
- Thinking natural always means safe. Many plant poisons are natural.
- Thinking synthetic always means bad. Most modern medicines are synthetic and tested carefully.
- Thinking a drug works anywhere in the body. It works only where its target is.
- Mixing up nanomedicine with a new drug. The drug can be old; the nano part is the carrier.