Key Terms You Must Know

📖 Key Terms You Must Know

Penicillin

The world's first broad-spectrum antibiotic, derived from the Penicillium mould. Discovered accidentally by Alexander Fleming in 1928, developed as a usable drug by Howard Florey and Ernst Chain (1939–41), and mass-produced with US government support by 1944. Unlike magic bullets (which targeted one specific disease), penicillin was effective against a wide range of bacterial infections including blood poisoning, pneumonia, wound infections, and gonorrhoea. It transformed medicine by providing, for the first time, a reliable cure for infections that had previously been almost always fatal.

Antibiotic

A substance produced by a microorganism (or synthetically manufactured) that kills or inhibits the growth of bacteria. Penicillin was the first naturally derived antibiotic — it worked by preventing bacteria from forming cell walls, causing them to burst. Antibiotics are distinct from antiseptics (which kill germs on external surfaces) and from magic bullets/sulphonamides (which are synthetic chemicals). The antibiotic era beginning with penicillin transformed the treatment of bacterial infection and is estimated to have saved hundreds of millions of lives.

Alexander Fleming (1881–1955)

Scottish bacteriologist who accidentally discovered penicillin in 1928 when he noticed that Penicillium mould was killing bacteria on a contaminated petri dish. He named the active substance penicillin, published his findings, but was unable to purify it in sufficient quantities for clinical use. He moved on to other research and the discovery lay largely unused for a decade. He shared the 1945 Nobel Prize with Florey and Chain. For the AQA exam, Fleming represents the "chance" factor — his discovery was accidental, and he is contrasted with Ehrlich (systematic method).

Howard Florey and Ernst Chain

The Oxford scientists who transformed Fleming's accidental observation into a usable drug. Florey (Australian pharmacologist) and Chain (German refugee biochemist) worked together from 1939, developed methods to purify and concentrate penicillin, tested it on mice in 1940, and conducted the first human trial in 1941. They are arguably more important than Fleming in the practical development of penicillin as a treatment. Both shared the 1945 Nobel Prize with Fleming. For the AQA exam, they represent "individual determination" and "systematic scientific method."

Deep fermentation

The industrial production method developed by US scientists in the early 1940s that made mass production of penicillin possible. Instead of growing penicillin mould on the surface of liquid in shallow containers, the method grew it in large, deep tanks with forced aeration — dramatically increasing the yield per unit of equipment. Combined with the discovery of a higher-yield mould strain from a Peoria market cantaloupe melon, deep fermentation allowed production to scale from laboratory quantities to industrial volumes capable of supplying an army.

Nobel Prize in Physiology or Medicine (1945)

Awarded jointly to Alexander Fleming, Howard Florey, and Ernst Chain for the discovery and development of penicillin. The shared award reflects the AQA lesson that the penicillin story was not the work of one individual but a collaboration across time: Fleming's chance observation, Florey and Chain's systematic development, and the industrial and governmental machinery that produced it at scale. Fleming received more public credit than Florey and Chain, partly because his story (accidental discovery) was more dramatic — but examiners know this is an oversimplification.