Amino Acids
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50 free Amino Acids trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Every protein in your body, from the enzymes digesting your lunch to the fibers in your muscles, is spelled out with the same alphabet of 20 amino acids. Each one has its own personality: some are oily, some carry a charge, one is barely there at all, and a few have turned up in places as unlikely as a blockbuster film plot and a rock from space. This quiz covers what a biology or biochemistry class expects you to know: what sets each of the 20 apart, the difference between essential and nonessential amino acids, how the one-letter code works, and how cells link amino acids into chains that become working proteins. It also tells the stories behind the names and discoveries, which is often the easiest way to make them stick. The questions run from kitchen-table trivia to exam-level detail, and every answer comes with a short explanation, so it works as a study check before a test as well as a round for quiz night.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Which amino acid is wrongly blamed for the drowsiness that follows a big Thanksgiving turkey dinner?
Tryptophan
Tryptophan takes the blame, yet turkey holds about as much of it as any other poultry. The body does turn it into serotonin and the sleep hormone melatonin.
Q 02Which amino acid, identified in kelp broth by a Tokyo chemist, gives food its savory umami taste?
Glutamate
Glutamate is the G in MSG: Kikunae Ikeda crystallized it from kombu broth in 1908 and named its taste umami. Aged cheeses and soy sauce are naturally rich in it.
Q 03In Jurassic Park, the dinosaurs are engineered to die without supplements of which amino acid?
Lysine
Lysine was the kill switch, known as the lysine contingency. Humans have no way of making it either, and simply get it from everyday foods such as eggs, meat and beans.
Q 04Which energy drink ingredient, a cousin of the amino acids, is named after the ox bile it came from?
Taurine
Taurine comes from taurus, Latin for bull or ox, because two German scientists first isolated it from ox bile in 1827. Cats must get it from their diet, so it is added to cat food.
Q 05Diet sodas sweetened with aspartame carry a warning for people with PKU about which amino acid?
Phenylalanine
Phenylalanine is released as the body digests aspartame, and people born with phenylketonuria cannot break it down. Left unchecked it harms the brain, so many countries screen every newborn.
Q 06What did Stanley Miller pass through a flask of simple gases to create amino acids from scratch?
Electric sparks
Electric sparks stood in for lightning in a mock early-Earth atmosphere, and amino acids formed. Sealed vials reopened after Miller's death in 2007 held even more of them than he had reported.
Q 07Which Google DeepMind AI system predicts a protein's 3D shape from its amino acid sequence alone?
AlphaFold
AlphaFold won its makers Demis Hassabis and John Jumper a share of the 2024 Nobel Prize in Chemistry. Sixty years of lab work had solved about 170,000 protein shapes out of some 200 million known proteins.
Q 08Which protein, the most abundant in mammals, holds together skin, tendons, cartilage and bone?
Collagen
Collagen makes up a quarter to a third of all the protein in a mammal's body. Its three chains twist into a rope so tight that every third amino acid has to be the smallest one available.
Q 09Which legume is a complete protein, supplying enough of all nine essential amino acids?
Soybean
The soybean is unusual among plant foods in that respect, which is why tofu and soy milk can stand in for meat and dairy. Chickpeas and most other legumes run short of one essential amino acid.
Q 10Which hormone that drives labor contractions and milk release is a chain of just nine amino acids?
Oxytocin
Oxytocin is so small that in 1953 it became the first hormone of its kind to be built from scratch in a lab, earning Vincent du Vigneaud a Nobel Prize. Doctors still use the synthetic form to induce labor.
Q 11Which amino acid, the first ever isolated, was crystallized from the juice of a spring vegetable?
Asparagine
Asparagine turned up in asparagus juice in 1806, in the hands of French chemists Louis Nicolas Vauquelin and Pierre Jean Robiquet. Heated with sugars during cooking, it forms the chemical acrylamide.
Q 12Which amino acid is the simplest of the 20, with just a single hydrogen atom for a side chain?
Glycine
Glycine is also the only one of the 20 with no mirror-image twin, because its side chain is too plain to have one. Its name comes from the Greek for sweet, after the taste of its crystals.
Q 13Which amino acid forms the bridges in hair that a perm breaks and then rebuilds in a new shape?
Cysteine
Q 21Which element, absent from pure fats and carbohydrates, is found in every single amino acid?
Nitrogen
Nitrogen sits in the amino group that gives these molecules their name. Food labs exploit that: they estimate how much protein a food holds by measuring how much of the element it contains.
Q 22Nine of the 20 standard amino acids are labeled essential for adult humans for what reason?
The body cannot make them
The body cannot make them, so they have to arrive ready-made in food. The other eleven are just as vital to life; our cells simply build those for themselves.
Q 23Which small molecule is released each time two amino acids join together in a growing chain?
Water
Cysteine carries a sulfur-tipped side chain, and two of them can clasp together into a disulfide bridge. Perm lotion snaps those bridges, then a second lotion re-forms them around the curler.
Q 14Which amino acid is coded by AUG, the start signal that opens nearly every protein recipe?
Methionine
Methionine is therefore the first link laid down whenever a cell begins building a protein. It is also one of only two amino acids spelled by a single genetic word; most have several.
Q 15Which amino acid is the only one of the 20 whose side chain loops back to bond with its backbone?
Proline
Proline's rigid five-membered ring makes it a structural disruptor, breaking up the neat spirals and sheets of a folded protein. It is named after pyrrolidine, the ring it contains.
Q 16Which amino acid, the body's raw material for dopamine, is named after the Greek word for cheese?
Tyrosine
Tyrosine was discovered in 1846 by Justus von Liebig in casein, the main protein of cheese. The skin and hair pigment melanin is built from it too.
Q 17Which amino acid does the body turn into the allergy chemical that hay fever pills block?
Histidine
Histidine loses a single carbon dioxide group to become histamine, the trigger for the sneezing, itching and hives of an allergy. Antihistamine pills blunt its effects.
Q 18Which amino acid do blood vessel walls convert into nitric oxide, the gas that relaxes arteries?
Arginine
Arginine is the raw material for the gas, whose discovery as a blood vessel relaxer earned a 1998 Nobel Prize. Its name comes from the Greek for silver, after its silvery-white crystals.
Q 19Which branched-chain amino acid, abundant in whey, signals muscles to start building new protein?
Leucine
Leucine flips on mTOR, a master switch for growth inside muscle cells, which makes it the star of BCAA supplements. Its name comes from the Greek for white, the color of its powder.
Q 20Which amino acid gives its name to ALT, the enzyme measured in routine blood tests of liver health?
Alanine
Alanine aminotransferase, or ALT, is screened for because a raised level in the blood is an early flag for liver trouble. The amino acid itself was first made in a lab in 1850 and named in a nod to aldehyde.
Water is squeezed out as each link forms, which is why chemists call it a condensation reaction. Digestion runs the process in reverse, adding the molecule back to split proteins apart.
Q 24Which cell structure reads a genetic message and links amino acids together into a protein chain?
Ribosome
The ribosome of a bacterium differs enough from ours that some antibiotics kill germs simply by jamming theirs. Every living cell depends on these molecular machines.
Q 25What name do chemists give the link that joins one amino acid to the next in a protein chain?
Peptide bond
A peptide bond forms when the acid end of one amino acid reacts with the amine end of the next. The name goes back to Emil Fischer, who proposed in 1902 that proteins are chains built this way.
Q 26In sickle cell disease, a one-letter gene change swaps which amino acid into hemoglobin?
Valine
Valine leaves an oily patch on hemoglobin where a charged amino acid used to be, and the molecules stick together into long stiff chains that bend the red cell into a crescent.
Q 27Which amino acid was first obtained from silk protein, and takes its name from the Latin for silk?
Serine
Serine was first obtained from silk in 1865 by Emil Cramer, and the fiber remains a particularly rich source of it. Its name comes from sericum, the Roman word for the fabric.
Q 28Which amino acid, the last of the 20 to be discovered, was found by nutrition chemist William Rose?
Threonine
Threonine turned up in 1935, after Rose found that the 19 amino acids then known were not enough to sustain growth. The hunt let him map exactly which amino acids a diet must supply.
Q 29Which amino acid, a major fuel for intestinal cells, is the most abundant one free in human blood?
Glutamine
Glutamine also serves as the bloodstream's safe carrier for ammonia, ferrying the toxic waste away for disposal. Its one-letter code in protein sequences is Q.
Q 30Which tough structural protein makes up human hair and fingernails as well as rhino horn?
Keratin
Keratin also builds feathers, claws, hooves and the outer layer of your skin. Even the slime threads of the hagfish, an eel-shaped sea creature, are made of it.