The Very Edible Organic Chemistry Quiz

Answer: caffeine

Caffeine belongs to a class of organic compounds called alkaloids (as does nicotine). Caffeine is a powerful stimulant of the central nervous system. It is usually present in coffee in the amount of 100-150 mg per cup (of course in decaf, there is virtually none!). Like many alkaloids, caffeine acts as a poison in large quantities.

The lethal dose of caffeine for adults is estimated at about 10 g, so unless you drink about 70-100 cups of coffee a day, you should be safe!

Answer: sugar

"Sugar" as we know it is the generic term given to sucrose. However, "sugar" is a term that is given to a whole range of compounds of a certain general structure that display sweetness as a physical property. More complicated sugars are all based on the linking together of small sugar units such as glucose. Sucrose is a disaccharide, which means that its structure is composed of two sugar units - in this case one unit of glucose and one unit of fructose.
Sucrose can be obtained from sugar cane (approx 20% by weight) or sugar beets (15% by weight).

Answer: baking soda

Sodium bicarbonate (chemical formula NaHCO3) is what makes cakes rise. This is because when it's mixed with water, it forms carbon dioxide (CO2). These bubbles of carbon dioxide are what make the cake rise and give it a light texture. Self-raising flour has a small amount of sodium bicarbonate already added to it.

Answer: vinegar

Acetic acid (chemical formula CH3COOH) is the major component of vinegar. Acetic acid belongs to the chemical family of carboxylic acids. These acids all contain an -OH group bonded directly to a carbonyl (C=O) group. Formic acid (found in ants) and butyric acid (found in your stomach) are other examples of carboxylic acids. Butyric acid is also what gives rancid butter its smell - in fact, the word "butyric" is derived from the Latin word "butyrum", meaning butter.

Answer: onions

Onions contain a chemical called propanethial S-oxide, which is responsible for the tears you cry when chopping them. Chemical words containing "thia" or "thio" in them mean that they are sulphur-containing compounds. Many sulphur-containing compounds have particularly disagreeable smells (volatile sulphur-containing compounds are added in small quantities to natural gas so that you can smell it).

It has recently been discovered that an enzyme in the onion is responsible for making propanthial S-oxide, and researchers have suggested that genetic modification may be the way to tear-free onions. In the meantime, tips to reduce those tears when handling onions include slicing them under water and only slicing the top off the onion before chopping (the root apparently has the highest concentration of sulphur-containing compounds).

Answer: salt

Sodium chloride is common table salt. Sodium chloride (NaCl) is an ionic compound whose structure consists of a regular 3-dimensional lattice of sodium ions and chloride ions. Although the body needs sodium to function properly, too much salt in the diet can lead to fluid retention which in turn may lead to hypertension and stroke. Salt substitute can be purchased in some supermarkets: this is simply potassium chloride, which has the taste of sodium chloride, but no sodium ions.

Answer: chocolate

Phenylethylamine belongs to a class of organic compounds called amines. Amines feature a nitrogen atom bonded to one or more carbon-based groups. Phenylethylamine is also produced naturally by the brain, and its effect is to produce a general sense of wellbeing or happiness. No wonder eating chocolate makes us happy! ;)

Answer: orange

Limonene is a pleasantly citrus-smelling compound found in most citrus fruits such as oranges, lemons and limes. Limonene is an example of a terpene (see my quiz "Common names of Organic Molecules II"). Limonene is used as a solvent in degreasing metals prior to industrial painting, for cleaning in the electronic and printing industries, and in paint as a solvent.

It is also used as a flavour and fragrance additive in food, household cleaning products, and perfumes. It can be easily obtained from most citrus fruits by steam distillation.

Answer: chillies

Capsaicin (and the related capsaicinoids) is the chemical present in chillies (and all peppers) that gives them their well-known heat. Capsaicin is another example of an amine (see question 7). When eaten, the capsaicinoids in chillies bind to a receptor in the lining of the mouth.

This is the same receptor that registers pain from heat, thus the effect is a burning feeling. If you find yourself in dire straits after eating a too-hot chilli, you'll get relief from drinking a glass of milk.

Answer: carrot

Beta-carotene is a naturally-occurring pigment responsible for the bright orange colour of carrots (I guess it's not hard to see where its name comes from!). Beta-carotene has an extremely important role in relation to vitamin A, the vitamin that is essential for our eyes. Vitamin A is an alcohol (a molecule containing an -OH group) whose structure is exactly one half of that of beta-carotene. Cleavage of beta-carotene by an appropriate enzyme gives two molecules of vitamin A. Thanks for playing this quiz; I hope you enjoyed it. If you did, check out my other quizzes in the Organic Chemistry section.