Q 01/05

Caffeine keeps you awake mainly by blocking the receptors of which sleep-promoting molecule?

A) Adenosine

B) Serotonin

C) Melatonin

D) Histamine

Answer · why

A) Adenosine

The molecule builds up in the brain the longer you stay awake; caffeine has a similar shape and sits in its receptors without switching them on.

Q 02/05

To which chemical class of stimulants does caffeine belong?

A) Cannabinoids

B) Opioid alkaloids

C) Methylxanthines

D) Amphetamines

Answer · why

C) Methylxanthines

Its cousins theophylline and theobromine, found in tea and chocolate, are also methylxanthines and are used to treat asthma.

Q 03/05

Caffeine is chemically related to which components of DNA and RNA?

A) The sugar deoxyribose

B) The bases adenine and guanine

C) The bases cytosine and thymine

D) The phosphate backbone

Answer · why

B) The bases adenine and guanine

It is a purine alkaloid, a bitter white crystalline solid.

Q 04/05

What title does caffeine hold among the world's psychoactive substances?

A) The most strictly regulated

B) The most widely consumed

C) The most addictive

D) The most recently discovered

Answer · why

B) The most widely consumed

Global consumption is estimated at 120,000 tonnes a year, and unlike almost every other psychoactive drug it is legal nearly everywhere.

Q 05/05

Why do plants such as coffee and tea make caffeine in the first place?

A) As a natural pesticide against insects

B) To attract pollinating bats

C) To make their leaves taste sweet

D) To store energy for winter

Answer · why

A) As a natural pesticide against insects

It can paralyse and kill insects, and it leaches into the soil to stop rival seeds germinating near coffee seedlings.