Q 01/05

Most of the world's citric acid is not squeezed from fruit but made by feeding sugar to which organism?

A) A red seaweed

B) A black mould

C) A soil bacterium

D) A green alga

Answer · why

B) A black mould

A black mould, Aspergillus niger, is the workhorse of the citric acid industry. The same species causes the sooty rot sometimes found on onions and gr...

Q 02/05

Which American drug company, later known for a COVID-19 vaccine, owed its early growth to making citric acid?

A) Moderna

B) Novavax

C) Merck

D) Pfizer

Answer · why

D) Pfizer

Pfizer grew on citric acid from the 1880s. Its later skill at fermenting the acid in deep tanks was the same know-how it used to mass-produce penicill...

Q 03/05

The citric acid cycle, which releases energy from food inside cells, is also named after which Nobel laureate?

A) Hans Krebs

B) Linus Pauling

C) Frederick Sanger

D) Otto Warburg

Answer · why

A) Hans Krebs

Hans Krebs identified the cycle in 1937 and won the Nobel Prize in Physiology or Medicine in 1953, sharing it with Fritz Lipmann.

Q 04/05

Which toiletry, invented by Lush co-founder Mo Constantine, relies on citric acid reacting with baking soda?

A) Shower gels

B) Dry shampoos

C) Bath bombs

D) Shaving foams

Answer · why

C) Bath bombs

Bath bombs were invented in 1989 in a shed in Dorset. Dropped in water, the acid and the soda react and release a stream of gas bubbles.

Q 05/05

Which famous impotence drug, approved in 1998, contains its active ingredient sildenafil as a salt of citric acid?

A) Cialis

B) Viagra

C) Levitra

D) Stendra

Answer · why

B) Viagra

Viagra is sildenafil citrate. The compound was first studied as a treatment for high blood pressure and angina before its more famous effect showed up...