Enzymes
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50 free Enzymes trivia questions with answers — science & nature quiz, new questions added Oct 2026.
Enzymes are the molecules that make life's chemistry fast enough to keep a cell alive. Bread, beer, medicines and modern DNA testing all depend on them too, which makes them one of the most useful topics in biology to understand properly. This quiz covers how enzymes work and what shapes their activity: heat, pH, helper molecules and inhibitors. It also visits the digestive system, the enzymes behind well-known drugs and poisons, the tools of genetic engineering, and the scientists who worked out the rules. The early questions suit GCSE and high-school biology revision, and the later ones reach into A-level, AP and first-year biochemistry. Every answer comes with a short explanation, so a wrong guess still teaches something.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Taq polymerase, the heat-proof enzyme behind PCR, came from bacteria found in which national park?
Yellowstone
Yellowstone's Mushroom Spring gave science Thermus aquaticus, whose enzyme survives 95 °C. That let PCR copy DNA through repeated heating without fresh enzyme being added for every cycle.
Q 02Adults who cannot digest the sugar in milk make too little of which enzyme in the small intestine?
Lactase
Lactase splits milk sugar into two simpler sugars that the gut can absorb. In most of the world's population, the body makes far less of it after weaning.
Q 03Which painkiller, first sold by Bayer, permanently disables the COX enzymes that make prostaglandins?
Aspirin
Aspirin shuts the enzyme down for good, while ibuprofen only blocks it for a while. In platelets the block lasts for the cell's whole life of 8 to 9 days, which is why a small daily dose reduces clotting.
Q 04PETase, an enzyme from bacteria found near a Japanese recycling site, breaks down which material?
Plastic
Plastic of the PET type, used in drinks bottles, is what PETase cuts apart. The bacteria that make it were found in sludge and can feed on the carbon in the bottles.
Q 05Many meat tenderizers get their protein-cutting enzyme from the latex of which tropical fruit?
Papaya
Papaya latex is dried to make papain, the active ingredient in many commercial tenderizers. People who are allergic to latex may react to the fruit and its enzyme too.
Q 06Which model by Emil Fischer pictures a substrate fitting an enzyme's exactly matching pocket?
Lock and key
Lock and key was Fischer's image for why each enzyme accepts only its own substrate. Later work added flexibility: in the induced fit version, the pocket reshapes itself as the substrate binds.
Q 07Which mix of enzymes, traditionally taken from the stomachs of calves, curdles milk in cheesemaking?
Rennet
Rennet contains chymosin, which curdles the casein proteins in milk. Each ruminant makes its own version, so kid goat rennet is sold for goat's milk and lamb rennet for sheep's milk.
Q 08Which enzyme in saliva starts digesting starch, so that rice tastes sweeter the longer it is chewed?
Amylase
Amylase begins cutting starch into sugar before food is even swallowed. Some historic brewers relied on it, chewing grain so that their saliva would start the conversion.
Q 09Enzymes speed up reactions by lowering which barrier that reacting molecules must first overcome?
Activation energy
Activation energy is the push a reaction needs to get going, and enzymes often cut it enough to speed things up millions of times. The enzyme itself is not consumed, so it can work again and again.
Q 10Raised levels of the enzymes ALT and AST in a blood test usually point to damage in which organ?
Liver
Liver injury of almost any kind raises ALT, so doctors read the pair as markers of damage there. AST is the less specific of the two, because a variety of other tissues can release it.
Q 11Which protein-digesting stomach enzyme is most active in strong acid, at around pH 2?
Pepsin
Pepsin is released as inactive pepsinogen and only switches on when it meets the stomach's hydrochloric acid. Theodor Schwann, who discovered it, named it after the Greek word for digestion.
Q 12Which process, which also hardens a boiled egg, wrecks an enzyme's shape when it overheats?
Denaturation
Denaturation unravels the folded chain, so the enzyme's working pocket no longer fits its substrate. Strong acid, alcohol and radiation can do the same job as heat.
Q 13Which class of cholesterol-lowering drugs works by blocking the enzyme HMG-CoA reductase?
Statins
Q 21Which enzyme from the pancreas digests fats by cutting fatty acids off triglyceride molecules?
Lipase
Lipase uses water to clip the fatty acids from fat molecules. Related enzymes do very different jobs elsewhere in the body, including helping to build fat-based hormones.
Q 22Humans cannot digest the fiber in grass and paper because the body makes no version of which enzyme?
Cellulase
Cellulase is missing in most animals, and even cattle and sheep rely on gut bacteria to make it for them. The textile industry uses the enzyme for the 'biostoning' of jeans.
Q 23Which mold-derived antibiotic kills bacteria by jamming the enzymes that cross-link their cell walls?
Penicillin
Statins jam the enzyme at the center of the body's own cholesterol production. Natural versions are made by fungi, probably as a weapon against the microbes they compete with.
Q 14Test strips used by people with diabetes carry an oxidase enzyme that reacts with which sugar?
Glucose
Glucose oxidase pulls electrons from the sugar, producing a current in proportion to how much is there. Honeybees put the same enzyme into honey, where it acts as a natural preservative.
Q 15Most enzymes in the human body work fastest near which temperature, slowing sharply above it?
37 °C (99 °F)
37 °C is the average human body temperature, and the body's enzymes are tuned to work best close to it. Above 40 °C they quickly start to lose their shape.
Q 16Subtilisin, a protein-digesting bacterial enzyme, is made in bulk to cut stains in which product?
Laundry detergent
Laundry detergent uses it to break down protein stains such as blood and egg. Makers re-engineer the enzyme first, because the natural form is easily knocked out by detergents and heat.
Q 17The induced fit model likens an enzyme reshaping around its substrate to which item being put on?
A glove
A glove changes shape as a hand slides in, just as the enzyme's pocket shifts when its substrate arrives. Daniel Koshland proposed the idea in 1958 as a more flexible update of an older, rigid picture.
Q 18Which digestive fluid, stored in the gallbladder, breaks fat into droplets for enzymes to attack?
Bile
Bile works like a soap, coating fat droplets so that they cannot merge back together. The far larger surface area lets fat-splitting enzymes from the pancreas get to work.
Q 19ACE inhibitors, first modelled on a peptide in pit viper venom, are prescribed mainly to lower what?
Blood pressure
Blood pressure falls because the drugs block angiotensin-converting enzyme, which lets blood vessels relax. The snake's venom works the same way, by severely depressing blood pressure.
Q 20Most enzymes are proteins, long folded chains built from which small molecules in a set order?
Amino acids
Amino acids in their exact sequence decide how the chain folds, and the fold decides what the enzyme can do. Yet only around two to four of them usually carry out the actual chemistry.
Penicillin stops a growing bacterium from completing its wall. The enzymes it disables are named after the drug itself: biochemists call them penicillin-binding proteins.
Q 24Which enzyme, found in nearly all oxygen-exposed life, splits hydrogen peroxide into water and oxygen?
Catalase
Catalase is among the fastest enzymes known, with one molecule breaking down millions of hydrogen peroxide molecules each second. Labs test bacteria for it by watching for oxygen bubbles.
Q 25Which enzyme makes fireflies glow by oxidizing a light-emitting compound, using oxygen and ATP?
Luciferase
Luciferase also lights up click beetles. Because its reaction needs ATP, laboratories use the firefly enzyme widely in biotechnology.
Q 26Which fast-acting poison kills by blocking cytochrome c oxidase, the enzyme that lets cells use oxygen?
Cyanide
Cyanide leaves the body's tissues unable to use oxygen, however much is carried in the blood. Because that oxygen stays in the veins, a victim's skin can turn cherry red.
Q 27Which enzyme unzips DNA ahead of copying by breaking the hydrogen bonds between its two strands?
Helicase
Helicase is a motor protein that burns ATP as it travels along the DNA, prising the strands apart. Cells make many kinds, since copying, reading and repairing DNA all need the strands separated.
Q 28Which molecular scissors, such as EcoRI, do bacteria use on viral DNA and labs use for gene splicing?
Restriction enzymes
Restriction enzymes each recognize a specific short stretch of DNA and cut there. The name comes from studies of a virus whose growth was restricted inside certain host bacteria.
Q 29Which enzyme does the cutting in CRISPR gene editing, steered to its DNA target by a guide RNA?
Cas9
Cas9 is part of an immune system that bacteria use against viruses. In 2012 Jennifer Doudna and Emmanuelle Charpentier showed that a single guide RNA could aim it at chosen DNA sequences.
Q 30Which enzyme, the most abundant on Earth, grabs carbon dioxide from the air during photosynthesis?
Rubisco
Rubisco accounts for about half the soluble protein in the leaves of many plants. It is far from perfect, sometimes reacting with oxygen instead of carbon dioxide.