Enzymes: speeding up life’s chemistry — Biology, 14–17 years
Cells contain countless chemical reactions, but many would be far too slow at body temperature. Enzymes make selected reactions faster by providing a suitable place for molecules to react.
Molecular helpers
An enzyme is a protein shaped so that particular molecules can fit into part of it, called the active site. It helps those molecules react by lowering the energy barrier. The enzyme leaves the reaction unchanged, ready to work again.
Why reactions need help
Particles do not react merely because they are close; they must collide in a useful direction and with enough energy. At body temperature, many useful reactions would happen too rarely. Enzymes solve this timing problem without requiring cells to become dangerously hot.
Worked example: catalase
Hydrogen peroxide can damage cells, so catalase breaks it into water and oxygen. Add potato tissue to hydrogen peroxide: bubbles appear as oxygen forms. If boiling first stops the bubbles, heat has changed the enzyme’s shape, so its active site no longer works well.
Trap: enzymes add energy
It is reasonable to think a faster reaction must have received extra energy, like a pushed swing. An enzyme usually does not change the energy stored in the starting or ending substances. It lowers the barrier between them, so the same reaction happens more often and more quickly.
Use: washing with biological detergents
Biological detergents contain enzymes such as protease and lipase. Protease breaks down protein stains, while lipase acts on fats, helping at lower temperatures than plain water might need. The enzymes work on stains, not by magically dissolving every kind of dirt.
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