50 Fun Facts About Biochemistry

Which hormone was first injected into a patient in 1922, when Toronto doctors treated a dying 14-year-old boy?

Insulin had been isolated from dog pancreas only months earlier by Banting and Best. The extract given to the boy was so impure that he had a severe allergic reaction.

Which protein, the most abundant in mammals, turns into gelatin when animal bones and hides are boiled?

Collagen makes up 25% to 35% of all the protein in a mammal's body. It often survives in ancient bones, so it may be one of the most abundant proteins in the fossil record too.

Which tough protein forms human hair and fingernails as well as the horns of cattle and rhinos?

Keratin is rich in sulfur, which is why burning hair smells so pungent. The same protein family builds feathers, hooves, claws and the slime threads of hagfish.

Which stimulant fights drowsiness by blocking brain receptors for adenosine, which builds up during waking hours?

Caffeine sits in the adenosine receptor without switching it on, so the drowsiness signal never arrives. Heavy use makes the body produce more of those receptors.

Which sugar in milk are around 65% of adults worldwide unable to absorb fully?

Lactose is digested by an enzyme that most people make less of after infancy. Struggling with milk as an adult is the ancestral human state, and tolerance evolved later among dairy farmers.

Which iron-containing protein makes up about 96% of a red blood cell's dry weight and carries oxygen around the body?

Hemoglobin lets blood carry about seventy times more oxygen than could dissolve in plasma alone. Max Perutz worked out its molecular structure in 1959.

Which margarine ingredient, formed when vegetable oil is partially hydrogenated, did the US FDA rule unsafe in 2015?

Trans fats occur naturally in small amounts in meat and dairy, but the food industry had been making them in bulk since the early 1900s, first for margarine and then for snacks and baked goods.

Which nutrient can most animals make for themselves, although humans, guinea pigs and most bats must get it from food?

Vitamin C is out of human reach because mutations have broken a gene for one of the enzymes that make it. A rat simply builds its own supply from sugar.

Which chemist's PhD student took Photo 51, the 1952 X-ray image that proved critical evidence for the structure of DNA?

Rosalind Franklin had not given permission when Maurice Wilkins showed the image to Watson. It was the 51st diffraction photo her student Raymond Gosling had taken.

Which substance, the most abundant organic polymer on Earth, makes up about 90% of cotton fibre and nearly half of wood?

Cellulose passes through humans undigested, as dietary fibre. Cows and termites can live on it only because microbes in their guts break it down for them.

Which structures in human cells carry their own DNA, which is normally inherited only from the mother?

Mitochondria in a father's sperm are usually destroyed by the egg after fertilization. That is why genealogists can use their DNA to trace a maternal line far back in time.

Which carbohydrate, the most common in the human diet, turns an intense blue-black on contact with iodine solution?

Starch traps iodine inside the coils of its long chains, and that shifts the colour. Plants make it to store energy, which is why potatoes, rice and wheat are full of it.

Which waxy lipid, first identified in gallstones in 1769, is the raw material for the body's steroid hormones?

Cholesterol is made by the body's own cells, so the body does not rely on food for its supply. Other animals make it too, which is why all animal-based foods contain some.

Which yellow-green liquid, made by the liver and stored in the gallbladder, helps break up the fat in food?

Bile acts as a surfactant, spreading fat into tiny droplets much as washing-up liquid does. Its colour comes from two pigments, one orange-yellow and one green.

Which compound, produced in muscles during exertion, also gives yogurt and kefir their sour flavour?

Lactic acid was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Far from being mere waste, it is burned as fuel by the heart, the brain and resting muscle.

Which Y-shaped proteins does the immune system use to identify and neutralize invaders such as bacteria and viruses?

Antibodies go on being made long after an infection is over. Some of the plasma cells that secrete them can potentially live for a person's whole lifetime.

Which elastic network of proteins forms when wheat flour is wetted and kneaded, giving bread dough its stretch?

Gluten is built from two kinds of protein in the grain, gliadin and glutenin, linking up. Around 1–2% of people have celiac disease and cannot tolerate it.

Which process, in which water crosses a membrane toward the more concentrated side, is how table salt kills slugs?

Osmosis is also why a potato slice shrinks in salty water. The stronger the salt solution, the more size and weight the slice loses.

In which US national park was the bacterium found whose heat-proof enzyme, Taq polymerase, makes PCR tests possible?

Yellowstone received no share of the profits made from the enzyme. Thomas Brock and Hudson Freeze had isolated the microbe from the park's Mushroom Spring in the 1960s.

Which sea animal first yielded green fluorescent protein, the glowing tag behind the 2008 Nobel Prize in Chemistry?

Jellyfish of the species Aequorea victoria carry the protein in small granules around the rim of the bell. Nobody knows what purpose the glow serves.

Which element, first isolated in 1669 by an alchemist boiling down urine, is part of the framework of DNA?

Phosphorus glowed in the dark when Hennig Brand first made it, while hunting for the philosopher's stone. It is the first element whose discoverer and date of discovery are on record.

Which French scientist first showed that molecules can be left- or right-handed, using tartrate crystals in 1848?

Louis Pasteur noticed that half the crystals were mirror images of the other half. He worked out that a lopsided arrangement inside each molecule was what twisted light one way or the other.

Which amino acid, wrongly blamed for drowsiness after a turkey dinner, does the body turn into serotonin?

Tryptophan is no more plentiful in turkey than in other poultry. The carbohydrates served alongside the bird are a likelier cause of the slump after a big meal.

Which amino acid did Kikunae Ikeda isolate from kelp broth in 1908 as the source of the savoury taste umami?

Glutamate also adds to the flavour of meat and tomatoes, as Ikeda went on to confirm. His search began with a bowl of soup that tasted better than usual because of the kombu in it.

Which infectious agent, a misfolded protein containing no DNA or RNA, is the hypothesized cause of mad cow disease?

Prion is a word Stanley Prusiner built from 'protein' and 'infection'. He won the 1997 Nobel Prize in Physiology or Medicine for his research into them.

Which two-object analogy sums up Emil Fischer's 1894 idea that an enzyme and its substrate have matching shapes?

Lock and key was revised in 1958 by Daniel Koshland, who pointed out that enzymes are flexible. In his version the enzyme is reshaped as the substrate binds to it.

Which enzyme in human saliva can make rice and potatoes taste sweet as they are chewed?

Amylase begins digestion in the mouth, cutting long carbohydrate chains down into sugar. The pancreas makes it as well as the salivary glands.

Which solvent, a main ingredient of many nail polish removers, gives the breath a fruity smell during ketosis?

Acetone forms when the liver breaks down fat rapidly, as in a long fast or a very low-carb diet. It is so volatile that it passes from the blood into the air a person breathes out.

Which popular dietary supplement, named from the Greek word for meat, helps muscle and brain cells recycle ATP?

Creatine was first isolated from skeletal muscle in 1832 by the French chemist Michel Eugène Chevreul. Products built around it for strength training did not go on sale until 1993.

Which DeepMind AI program, whose developers shared the 2024 Nobel Prize in Chemistry, predicts protein structures?

AlphaFold learned its craft from more than 170,000 known protein structures held in a public database. Demis Hassabis and John Jumper took half of the prize for it.

Which branched molecule do the liver and muscles build out of glucose as the body's short-term energy store?

Glycogen in an adult liver adds up to only about 100 to 120 grams. That small reserve keeps blood sugar steady between meals, above all for the brain and nerves.

Which sequence of ten enzyme reactions, found so widely that it must be ancient, converts glucose into pyruvate?

Glycolysis in its commonest form is called the Embden–Meyerhof–Parnas pathway, after three of its discoverers. It takes place in the cytosol, the liquid part of the cell.

Which biochemist, dismissed in Germany in 1933 for his Jewish ancestry, identified the citric acid cycle in Sheffield?

Hans Krebs worked out the cycle in 1937 with William Arthur Johnson, and it earned him the 1953 Nobel Prize in Physiology or Medicine. Nature turned down his first report of it for lack of space.

Which link joins one amino acid to the next in a protein chain, releasing a molecule of water as it forms?

A peptide bond joins the carboxyl group of one amino acid to the amino group of the next. Chemists class the reaction as a condensation because of the water it gives off.

Which inherited condition did Linus Pauling call "a molecular disease" in 1949, blaming an abnormal protein molecule?

Sickle cell anemia comes down to a single amino acid swapped for another in one protein. The gene persists because carriers are protected to some degree against malaria.

Which enzyme, found in nearly all organisms exposed to oxygen, breaks hydrogen peroxide down into water and oxygen?

Catalase is one of the fastest enzymes known: a single molecule can convert millions of hydrogen peroxide molecules every second. The bubbles of oxygen it gives off serve as a lab test for bacteria.

Which enzyme, the most abundant on Earth, lets plants turn carbon dioxide from the air into sugars?

Rubisco accounts for about half of the soluble protein in the leaves of many plants. It works in the part of photosynthesis that does not need light.

Which base does RNA use in place of the thymine found in DNA, pairing it with adenine?

Uracil is simply thymine with one methyl group missing. In RNA it holds on to adenine through two hydrogen bonds.

Which British biochemist won the Nobel Prize in Chemistry twice, first for finding the amino acid sequence of a protein?

Frederick Sanger won in 1958 for sequencing proteins and again in 1980 for a way of reading DNA. His first prize showed that every protein has one unique, definite structure.

Which sulfur-containing amino acid forms the disulfide bonds that hold many proteins in shape?

Cysteine for industry is mostly obtained by breaking down poultry feathers or hog hair. Despite a widespread rumour, human hair is rarely the raw material.

Which British biochemist won the 1978 Nobel Prize in Chemistry for showing how proton gradients power ATP synthesis?

Peter Mitchell did much of the work at Glynn House, a Cornish mansion he had partly converted into a research laboratory. The later discovery of the enzyme that makes ATP vindicated his hypothesis.

Which animal's meat gave John Kendrew the myoglobin that in 1958 became the first protein with a known 3D structure?

A whale suited him because the muscle of diving mammals is rich in the oxygen-storing protein. A chance encounter brought him a large chunk of the meat from Peru, and it gave big, clean crystals.

Which Canadian physician co-wrote the 1913 paper behind the best-known equation for the rate of enzyme reactions?

Maud Menten had moved to Berlin in 1912 to work with Leonor Michaelis, whose name comes first in the equation. She was among the first women in Canada to earn a medical doctorate.

Which American chemist, who lost an arm in a hunting accident at 17, showed in 1926 that enzymes can be crystallized?

James Sumner spent years on an enzyme from jack beans while colleagues doubted that the task was possible. He was the first to show that an enzyme is a protein, and shared the 1946 Nobel Prize in Chemistry.

Which bacteria-killing enzyme did Alexander Fleming find in nasal mucus, years before he discovered penicillin?

Lysozyme is abundant in tears, saliva and human milk, and egg white holds large amounts of it. Fleming coined the name after watching the substance dissolve bacteria.

Which two ions does the membrane pump discovered by Jens Christian Skou in 1957 move in and out of animal cells?

Sodium and potassium swap unevenly: three ions of the first leave the cell for every two of the second that enter. Keeping that up takes around 30% of a typical cell's ATP.

Which term describes a molecule, such as an amino acid, that carries equal numbers of positive and negative charges?

Zwitterion comes from the German word Zwitter, meaning hermaphrodite. Chemists also call a molecule of this kind an inner salt or a dipolar ion.

Which protein shape did Linus Pauling first model in 1948 by folding a strip of paper while in bed with a cold?

The alpha helix reached print in 1951, after Pauling had worked with Robert Corey and Herman Branson to confirm the model. He had sketched the chain on the paper out of boredom.

Which 1972 model by Singer and Nicolson describes proteins scattered through the lipid layer of a cell membrane?

The fluid mosaic model treats the membrane as a two-dimensional liquid in which the embedded proteins are spread more or less at random. Later microscopy upheld the fluid picture but found the proteins less randomly placed.

Which metal ion sits at the centre of the B12 molecule, whose structure Dorothy Hodgkin solved in the 1950s?

Cobalt has to be in an animal's diet before its gut bacteria can make B12. That is why livestock grazing on soil that lacks the metal may need supplements or injections.