The Chemistry of Living Trivia Quiz

Answer: a metal complex

Haemoglobin is red in colour because of the iron complexed in the molecule. The iron is at the centre of a porphyrin ring, which is made up of nitrogen-containing rings joined together to make one big heterocyclic structure (a heterocycle is a molecule containing rings of carbon atoms plus other atoms such as nitrogen and/or oxygen).

The iron is complexed via the nitrogen atoms' lone electron pairs. Haemoglobin is vital for transporting oxygen around the body. Arterial blood is bright red in colour because of the oxygen coordinated to haemoglobin; when the oxygen is removed, water takes its place and venous blood changes colour to a dark purplish red.

Answer: hydrogen bonding

Hydrogen bonding is the strongest intermolecular force and occurs between electronegative atoms bearing lone pairs of electrons (such as nitrogen and oxygen) and hydrogen atoms attached to another electronegative atom. The phosphate-sugar backbone of each strand of DNA has a series of heterocyclic bases attached to it.

These bases contain nitrogen atoms that enable the complementary strands to hydrogen bond to each other, thus forming the double helix that we all recognise as DNA.

Answer: hydrolysis of an ester group

Lipases catalyse the hydrolysis of ester (RCOOR) groups as part of their role in the digestion of fats. Hydrolysis of esters is often carried out in the lab using aqueous sodium hydroxide (NaOH) at reflux - not an option in our bodies! Other types of enzymes include decarboxylases (catalysing the loss of carbon dioxide), dehydrases (catalysing the loss of water) and dehydrogenases (catalysing the loss of hydrogen and the formation of a double bond).

Answer: amino acids

Proteins are made up of different amino acids (there are 20 common amino acids) joined together. Amino acids contain both an amine (-NH2) group and a carboxylic acid (RCOOH) in the same molecule. They join together through the amine group of one molecule reacting with the carboxylic acid portion of another.

This makes a new functional group generally called an amide, but when the end product is a protein, this new link is called a peptide bond. As mentioned in question 1, haemoglobin is involved in transporting oxygen around the body.

Insulin is the hormone responsible for controlling glucose metabolism and keratin is found in wool, feathers, hooves, silk and fingernails.

Answer: Vitamin A

Beta-carotene (see my earlier quiz, "The Very Colourful Chemistry Quiz") is an orange pigment found in both carrots and orange skins. Vitamin A is synthesised in our bodies from beta-carotene by cleavage of the latter through a carbon-carbon double bond.

This cleavage is accomplished by enzymes in the liver, with one molecule of beta-carotene giving two molecules of Vitamin A. Vitamin A is then further converted to produce cis-retinal, which is the light-sensitive pigment on which our visual system is based. Cis-retinal then combines with a protein called opsin to produce rhodopsin.

When light strikes rhodopsin, it isomerises (changes the orientation of some of its atoms); this isomerisation is the trigger for a nerve impulse to the brain.

Answer: hydrochloric acid

The stomach contains hydrochloric acid (HCl), which helps break down food. The pH (a measure of the acidity of a particular solution - a pH of 7 is neutral; lower than 7 is acidic and higher than 7 is basic) of the digestive fluid in our stomach is around 1.0-2.0 (concentrated hydrochloric acid has a pH of approximately -1, while the average soft drink has a pH of around 3.0).

The enzyme pepsin, which is one of the enzymes responsible for digestion, requires this highly acidic environment in order to be active. Our stomach lining is protected from the acidity of the gastric fluid by a layer of mucous. If this mucous layer is damaged or worn away, then the acidic gastric fluid can eat away at the stomach lining, causing ulcers.

Answer: carbon dioxide

One of the waste products of our digestive process is carbon dioxide (CO2), which is exhaled through the lungs. The citric acid cycle is also known as the Krebs cycle, named after Hans Krebs, who elucidated the process in 1937. The energy produced in the citric acid cycle is then used in the electron transport chain, which produces molecules of ATP (adenosine triphosphate).

The use and production of energy in living things revolves around the interconversion of ATP to ADP (adenosine diphosphate) and the reverse.

Answer: It will oxidise the toxic substance.

Oxidation is pretty much what its name sounds like - one definition is the addition of oxygen atoms to a molecule. The body contains enzymes, such as cytochrome P-450, capable of oxidising toxic substances. It seems that, in general, the more oxygen atoms a molecule contains in comparison to its original structure, the less toxic it is to us.

A good example of this is the relative toxicity of benzene and toluene. Both have similar structures - benzene is a ring of 6 carbon atoms containing alternating single and double bonds; toluene is just a benzene ring with a methyl (-CH3) group attached to it.

However, the benzene ring is resistant to oxidation, causing benzene to be much more toxic than toluene, whose methyl group is oxidised much more rapidly than the benzene ring, allowing it to be excreted more quickly.

Answer: All of these.

The name "prostaglandin" derives from the fact that these compounds were first isolated from a sheep's prostate gland. It is now known that they are present, albeit in small amounts, in all tissues in the body. There are several dozen known prostaglandins, and their effects are wide-ranging - from lowering blood pressure to affecting blood-platelet aggregation during blood clotting, from affecting kidney function to controlling inflammation. Prostaglandins are synthesised from arachidonic acid in two steps using a cyclooxygenase (COX) enzyme.

The pain relief you get from taking an aspirin or any other non-steroidal anti-inflammatory drug is from the drug blocking the COX enzyme from making prostaglandins, which results in a decreased response by the body to inflammation.

Answer: sulphur

Proteins are usually said to have primary, secondary, tertiary and even quaternary structures. The primary structure is simply the amino acid sequence, the secondary structure is how certain sections of amino acids arrange themselves, the tertiary structure is how the whole protein molecule arranges itself to form a 3-dimensional structure and the quaternary structure describes how different protein molecules aggregate together to form other structures. Sulphur plays an important part in a protein's tertiary structure by being able to form disulphide (S-S) bonds.

The amino acid cysteine contains a sulphur atom, so any protein featuring this amino acid has the potential to make disulphide bridges in its tertiary structure provided the cysteine units are oriented correctly.

As an aside, disulphide bonds are what make vulcanised rubber (used in tyres) stronger and more durable than unvulcanised rubber. Thanks for playing this quiz; I hope you enjoyed it.