50 Fun Facts About Proteins

Rhinoceros horn is made of which protein, the same material found in human hair and fingernails?

Keratin also builds feathers, claws, hooves and the outer layer of skin. Rhino horn has no proven health benefits, whatever the poaching trade claims.

Miraculin, a protein from a West African berry, binds to taste receptors and makes sour foods taste how?

Sweet is how lemons and limes taste for an hour or two after miraculin coats the tongue. The protein has no sugary taste of its own.

Green fluorescent protein, which earned a 2008 Nobel Prize, was first isolated from which glowing sea animal?

Jellyfish of the species Aequorea victoria supplied the first GFP. Scientists now fuse its gene to other genes to watch proteins light up inside living cells.

Which infectious misfolded proteins, containing no DNA or RNA, cause mad cow disease in cattle?

Prions spread by forcing normal copies of the same protein to misfold. Stanley Prusiner coined the name by blending protein and infection.

Which structural protein, the most abundant in mammals, takes its name from the Greek word for glue?

Collagen makes up 25% to 35% of the protein in a mammal's body. Doctors use it in artificial skin to help severe burns heal.

Octopus blood is blue because the protein hemocyanin carries oxygen using which metal instead of iron?

Copper atoms in hemocyanin turn blue when they bind oxygen and go colourless when they let it go. The protein was first found in the common octopus in 1878.

Which amino acid is wrongly blamed for making people sleepy after a Thanksgiving turkey dinner?

Tryptophan is no more plentiful in turkey than in other poultry. The slump after a feast may come from the other foods eaten alongside the bird.

Antarctic notothenioid fish survive in subzero seawater because proteins in their blood act as what?

Antifreeze proteins bind to small ice crystals and stop them growing. Antarctic fish and northern cod evolved theirs separately.

Which oxygen-binding protein in muscle is the pigment responsible for the colour of red meat?

Myoglobin turns brown as its iron changes state in cooking, which is why a well-done steak loses its red. Cured ham stays pink because nitrites lock the pigment.

Which hormone became the first protein to be fully sequenced, work that won Frederick Sanger a Nobel Prize?

Insulin's sequence proved that a protein has one exact order of amino acids. Before the human form could be made in bulk, diabetics relied on insulin taken from pigs.

Which iron-containing protein packs red blood cells and ferries oxygen from the lungs around the body?

Hemoglobin was the first protein to have its molecular mass worked out, calculated from the weight of the iron it carries.

Which tiny cell structure, first observed by George Palade in 1955, links amino acids into protein chains?

Ribosomes are themselves part protein: each has a small and a large subunit built from RNA and many proteins.

Which Y-shaped proteins does the immune system use to identify and neutralise bacteria and viruses?

Antibodies are also known as immunoglobulins. The tip of each arm of the Y works like a lock that fits one particular target.

What name is given to the unfolding of proteins that turns a clear raw egg white solid when cooked?

Denaturation is not only caused by heat. Pouring egg whites into a beaker of acetone turns them solid too.

Which elastic network of wheat proteins lets bread dough stretch, rise and keep a chewy texture?

Gluten forms when two wheat proteins, gliadin and glutenin, are wetted and kneaded together. It accounts for 75–85% of the protein in bread wheat.

Which protein family, named from the Latin for cheese, makes up about 80% of the protein in cow's milk?

Casein clumps into curd when milk is soured, the first step towards cheese. Human milk contains a much smaller share of it than cow's milk.

Which liquid byproduct of cheese-making is processed into a protein supplement popular for building muscle?

Whey is the liquid left behind when milk coagulates. Ricotta and Norwegian brunost are cheeses made from it.

Food labs estimate protein content by measuring which element, found in every amino acid but not in fat?

Nitrogen makes up about 16% of an average protein, so food labels simply multiply the amount measured by 6.25.

Gram for gram, protein supplies about 4 kilocalories, the same food energy as which other nutrient?

Carbohydrate and protein both yield about 17 kilojoules per gram, less than half the energy packed into the same weight of fat.

Which giant muscle protein has a full chemical name of 189,819 letters, sometimes called the longest word in English?

Titin takes its name from the Titans of Greek myth. A single molecule strings together around 34,350 amino acids and acts as a spring inside muscle.

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

Peptide bond formation is a condensation reaction. Adding the water back, a step called hydrolysis, breaks the chain apart again.

What term describes the nine amino acids that the human body cannot make and must get from food?

Essential amino acids were pinned down by William Cumming Rose, who fed volunteers diets of purified amino acids and watched what happened when one was left out.

Which stomach enzyme, switched on by hydrochloric acid, begins breaking down the proteins in a meal?

Pepsin was one of the first enzymes ever discovered, by Theodor Schwann in 1836. He named it after the Greek word for digestion.

Which childhood disease of severe protein deficiency is marked by swollen feet and a bloated belly?

Kwashiorkor comes from the Ga language of coastal Ghana and means roughly the sickness the baby gets when the new baby comes. It struck toddlers weaned early to make way for a younger sibling.

Which protein-rich food is made by coagulating soy milk and pressing the curds into solid white blocks?

Tofu making was first recorded in China during the Han dynasty. Zen Buddhist monks later introduced it to Japan.

Lentils, peas, beans and peanuts are protein-rich seeds from which family of plants?

Legumes house bacteria in their roots that enrich the soil, so farmers rotate them with other crops. The family's formal name is Fabaceae.

Fibroin, a tough protein made by larvae of the moth Bombyx mori, forms the filaments of which fabric?

Silk in its raw state is two fibroin filaments coated in a second, glue-like protein called sericin. Fibroin's tightly packed sheets give the thread its strength.

Which bacterial protein, considered the deadliest known natural substance, is injected in tiny doses to smooth wrinkles?

Botulinum toxin relaxes the facial muscles it is injected into, so the skin above them smooths out. The full effect typically shows about a week later.

Which lethal protein from castor beans killed dissident Georgi Markov, shot with a pellet from a modified umbrella?

Ricin does not dissolve in oil, so little of it ends up in the castor oil pressed from the same seeds. The leftover seed cake stays toxic unless heat-treated.

Clumps of amyloid beta and tangles of tau protein in the brain are the hallmarks of which brain condition?

Alzheimer's disease is defined by those two abnormal proteins. One builds up as plaques outside nerve cells and the other as tangles inside them.

Which stage of gene expression decodes a genetic message into a chain of amino acids, outside the cell nucleus?

Translation follows transcription, which first copies the gene into RNA. The name fits because the cell is converting the language of nucleic acids into the language of amino acids.

Which single-stranded molecule carries a gene's protein-building instructions out of the cell nucleus?

Messenger RNA went on to power the Pfizer and Moderna COVID-19 vaccines, and the research behind them earned the 2023 Nobel Prize in Physiology or Medicine.

What name is given to a three-letter unit of genetic code that specifies a single amino acid?

Codon by codon, nearly every living thing reads the same code, and the whole of it fits in a simple table of 64 entries.

Which amino acid does the genetic start signal AUG code for, placing it first in newly made protein chains?

Methionine opens the chain in animals, plants and fungi. Bacteria begin theirs with a slightly modified form of the same amino acid.

Which cell structure, likened to a post office, packages proteins into vesicles and sends them to their destinations?

Golgi apparatus enzymes also modify each protein on the way through, which helps decide where it ends up. Camillo Golgi identified the structure in 1898.

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

Alpha helix coils are the most common arrangement in the secondary structure of proteins. Pauling published the model in 1951 with Robert Corey and Herman Branson.

Which level of protein structure describes the overall three-dimensional shape of a single folded chain?

Tertiary structure in globular proteins tucks water-repelling amino acids into a core and leaves charged ones on the surface. This overall fold controls what the protein does.

A hair perm works by breaking and then re-forming which links between the protein chains of each strand?

Disulfide bonds are what give hair its elasticity. One perm lotion snaps them open, then a second closes them again in the shape of the curling rod.

Which helper proteins, many of them made in response to heat stress, assist other proteins to fold correctly?

Chaperones grip half-folded chains to stop them clumping together, a risk that rises when a cell overheats.

Which reagent, a staple of school food tests, turns mauve when protein is present in a sample?

Biuret reagent contains no biuret at all, despite the name. The label stuck because the biuret molecule happens to give the same positive result.

Which DeepMind AI program, honoured by the 2024 Nobel Prize in Chemistry, predicts the 3D structures of proteins?

AlphaFold topped the CASP prediction contest in 2020 with results described as transformational. Demis Hassabis and John Jumper shared the Nobel for it.

Which technique did John Kendrew use in the 1950s to solve the first protein structure, taken from a sperm whale?

X-ray crystallography is now used routinely to see how a drug grips its protein target. Kendrew's whale samples gave large crystals with clean diffraction patterns.

Which British scientist stated the central dogma, that information cannot pass from protein back to DNA or RNA?

Francis Crick first stated the idea in 1957 and published it the next year. His wording still holds, unlike a simpler two-step version popularised by James Watson.

Which online puzzle game let players model a monkey-virus enzyme in ten days, a problem unsolved for 15 years?

Foldit was founded at the University of Washington by protein scientist David Baker. The 2011 puzzle stayed open for three weeks, and gamers cracked it in half that time.

Which inherited disease is most often caused by the loss of one amino acid, phenylalanine, from the CFTR protein?

Cystic fibrosis leaves cells unable to move chloride properly, which is why unusually salty sweat is a classic sign. Newer drugs act directly on the faulty protein.

Which motor protein drives muscle contraction by using ATP to walk along filaments of actin?

Myosin is so alike across species that the version from rabbit muscle will bind to actin taken from an amoeba.

Which fibrous protein forms a mesh over a platelet plug to complete a blood clot at a wound?

Fibrin does not circulate ready-made. The enzyme thrombin cuts it from a soluble blood protein, fibrinogen, at the site of a wound.

Which proteins act as spools for DNA to wind around, packing about 1.8 metres of it into each human cell?

Histones carry a positive charge that attracts the negatively charged backbone of DNA, which is what keeps the wrapping tight.

Which small protein tags other proteins for destruction, a signal nicknamed the molecular kiss of death?

Ubiquitin got its name because it is found ubiquitously, in most tissues. Working out how it sends proteins for recycling won the 2004 Nobel Prize in Chemistry.

Which Swedish chemist proposed the word protein in 1838, drawing on a Greek term meaning primary?

Jöns Jacob Berzelius suggested the name to his Dutch associate Gerardus Mulder, who had found that proteins all seemed to share nearly the same chemical formula.