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How Enzymes Work: Basics Explained

Here's how enzymes actually speed up the chemical reactions that keep you alive.

  1. What is an enzyme?

    An enzyme is a biological catalyst that speeds up the rate of chemical reactions in the body. Most enzymes are made of protein, and they aren't consumed or changed by the reactions they catalyze, so the same enzyme molecule can be reused again and again.

  2. How enzymes lower activation energy

    An enzyme works by lowering the activation energy β€” the minimum energy needed for a chemical reaction to occur β€” which lets the reaction happen much faster than it otherwise would.

  3. Substrate specificity (the lock-and-key model)

    Each enzyme has an active site with a unique three-dimensional shape, so it binds only to the specific substrate that fits that shape and catalyzes a reaction with it β€” a property called substrate specificity.

  4. The effect of temperature and pH

    Every enzyme has an optimal temperature and pH range at which it works most actively, and if conditions move far outside that range, the enzyme's protein structure can become distorted (denatured), causing it to lose its function.

  5. Examples of digestive enzymes

    Amylase in saliva breaks down carbohydrates, pepsin in the stomach breaks down proteins, and lipase secreted by the pancreas breaks down fats β€” a variety of enzymes are at work throughout the digestive system.

  6. Cofactors

    Some enzymes can't function properly on their own as proteins, and need to bind with a cofactor β€” such as a vitamin or a metal ion β€” before they can carry out their catalytic function.

  7. Enzyme inhibition

    Enzyme inhibition, in which a particular substance binds to an enzyme's active site or elsewhere and interferes with the reaction, is widely used in drug development and in regulating the body's metabolism.

A catalyst that speeds up the reactions of life

Most of the chemical reactions happening inside our bodies would occur very slowly at ordinary room temperature and pressure, but thanks to biological catalysts called enzymes, they can actually happen almost instantly. Enzymes are involved in nearly every activity of life, from digestion to breathing to muscle contraction.

Enzymes are made of protein, too

Most enzymes are made of protein, synthesized inside cells based on genetic information. If you're curious about the specific process by which proteins are made, that's covered in protein synthesis basics.

Frequently Asked Questions

Why can a high fever put stress on the body?

If body temperature moves far outside the normal range, the three-dimensional structure of enzymes in the body can become distorted and stop functioning properly β€” which is why keeping body temperature within a certain range is important for enzyme activity and metabolism.

Does an enzyme disappear after it's used once?

No. An enzyme returns to its original form unchanged after a reaction finishes, so the very same enzyme molecule can be used repeatedly, over and over, in many separate reactions.