Enzymes are proteins that speed up the chemical reactions that keep every living thing alive.
What are most enzymes made of?
Tiny living cells
Proteins
Sugars
Fats
Right! Most enzymes are proteins: long chains of amino acids folded into a precise 3D shape.
Most enzymes are proteins. They are folded chains of amino acids, not living cells, sugars, or fats, and their shape is what lets them work.
Catalase in your liver breaks down hydrogen peroxide. After it breaks down one molecule, what happens to the catalase?
It is used up in the reaction
It turns into water and oxygen
It breaks into amino acids
It is free to work again
Exactly! Enzymes are catalysts: they come out of the reaction unchanged and can be used again and again.
The catalase is free to work again. Enzymes aren't used up or changed into products; the hydrogen peroxide becomes water and oxygen, not the enzyme.
How do enzymes speed up chemical reactions?
By lowering the activation energy
By adding heat energy to molecules
By supplying extra energy to substrates
By making impossible reactions possible
Yes! Enzymes lower the activation energy, the energy hump a reaction must get over, so it happens much faster.
Enzymes lower the activation energy. They don't add energy, and they only speed up reactions that could happen anyway, just very slowly.
Scratch the card to reveal a fact about enzymes
Carbonic anhydrase, which helps remove carbon dioxide from your blood, can handle about a million molecules every second.
A human enzyme works best at 37°C. What happens if it is heated to 60°C?
It works twice as fast
It keeps speeding up steadily
Its active site loses its shape
It dies like a living cell
Correct! High heat breaks the bonds holding the enzyme's shape, so the active site changes and the enzyme is denatured.
Its active site loses its shape. Above its optimum temperature, an enzyme denatures and slows down or stops; it isn't alive, so it can't die.
An enzyme was denatured at 60°C. What happens when it is cooled back to 37°C?
It returns to full speed
It stays inactive
It slowly repairs itself
It splits into amino acids
That's it! Denaturing from heat is usually permanent, so the enzyme stays inactive, like a cooked egg white that can't turn clear again.
It stays inactive. Heat denaturing usually can't be undone, but the amino acid chain is still whole; only its folded shape is ruined.
Flip the card to discover an enzyme surprise
Fireflies glow thanks to an enzyme called luciferase, which turns chemical energy into light inside their bodies.
Did you know?
Enzymes are biological catalysts
Enzymes are used up in reactions
Each enzyme fits specific substrates
Enzymes are tiny living organisms
Saliva contains enzymes
Pepsin digests protein in your stomach. At about what pH does it work best?
About pH 7
About pH 8
About pH 11
About pH 2
Right! Pepsin works best around pH 2, matching the strong acid in your stomach.
Pepsin works best around pH 2. Each enzyme has its own optimum pH, and pepsin is adapted to the very acidic stomach, not neutral conditions.
Why does amylase break down starch but not protein?
It is too weak for protein
Protein needs a hotter temperature
Only starch fits its active site
It only works inside the mouth
Exactly! Enzymes are specific: only a substrate with the right shape fits the active site, like a key in a lock.
Only starch fits amylase's active site. Enzymes are specific to their substrate's shape; protein needs different enzymes, called proteases.
Where in the human body are enzymes found?
In almost every cell
Only in the stomach and gut
Only in the blood
Only in the liver
Yes! Enzymes work in nearly every cell, running processes like respiration, copying DNA, and building proteins.
Enzymes are found in almost every cell. Digestive enzymes are famous, but thousands of others run reactions all over your body.
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Can any enzyme survive near-boiling water?
Yes! Bacteria in hot springs make enzymes that work above 70°C, and one is used in labs to copy DNA.
Fresh pineapple has an enzyme that digests protein and stops gelatin from setting. Why does canned pineapple work fine?
The enzyme was used up in the can
Canning heat denatured the enzyme
The enzyme died inside the can
The can's juice is too acidic
Right! Canned pineapple is heated, which denatures the enzyme bromelain, so it can't break down the gelatin's protein anymore.
Canning heat denatured the enzyme. Pineapple's bromelain breaks down gelatin's protein, but heating during canning ruins its shape for good.
Biological laundry detergents contain enzymes. Why are they best used at about 40°C rather than 90°C?
Hot water uses up enzymes faster
Enzymes need cool water to live
Enzymes only work at body heat
High heat denatures the enzymes
Correct! Very hot water would denature the enzymes, so the protein- and fat-digesting enzymes couldn't remove stains.
High heat denatures the enzymes. Detergent enzymes are chosen to work well in warm water, but at 90°C their shape breaks down and they stop working.
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Question 1: What are most enzymes made of?
Question 2: Catalase in your liver breaks down hydrogen peroxide. After it breaks down one molecule, what happens to the catalase?
Question 3: How do enzymes speed up chemical reactions?
Question 4: A human enzyme works best at 37°C. What happens if it is heated to 60°C?
Question 5: An enzyme was denatured at 60°C. What happens when it is cooled back to 37°C?
Lightning round 1
Question 6: Pepsin digests protein in your stomach. At about what pH does it work best?
Question 7: Why does amylase break down starch but not protein?
Question 8: Where in the human body are enzymes found?
Question 9: Fresh pineapple has an enzyme that digests protein and stops gelatin from setting. Why does canned pineapple work fine?
Question 10: Biological laundry detergents contain enzymes. Why are they best used at about 40°C rather than 90°C?
Made with AI. This quiz was made with AI, which can make mistakes.
