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By the end of this subtopic, you should be able to:
Before we talk about enzymes, we need to understand what a catalyst is, because enzymes are a type of catalyst.
A catalyst is a substance that:
Think of a catalyst like a helper. Imagine you are trying to fold 100 pieces of paper. A helper speeds up the job — but the helper themselves is not destroyed in the process. They remain available to help with the next piece.
Key point: A catalyst increases the rate of a reaction. Without a catalyst, the reaction would still happen — just much more slowly.
Enzymes are the body's own special type of catalyst. Here is everything you need to know about them:
Enzymes are proteins. All enzymes are made of a type of molecule called a protein. Proteins are made of long chains of smaller building blocks called amino acids. These chains fold into a very specific three-dimensional (3D) shape — and this shape is absolutely critical to how the enzyme works.
Enzymes are biological catalysts. The word biological simply means "related to living things." Because enzymes are made inside living cells, they are called biological catalysts. Like all catalysts, they speed up chemical reactions without being used up or permanently changed.
Enzymes are involved in all metabolic reactions. Metabolism means all the chemical reactions that take place inside a living organism to keep it alive — things like breaking down food, building new cells, and releasing energy. Every single one of these metabolic reactions is controlled by enzymes. Without enzymes, these reactions would happen far too slowly to sustain life.
Why are enzymes so important? Consider digestion as an example. If you eat a meal, your body needs to break the food down into small molecules so it can be absorbed and used. Without digestive enzymes, this process would take weeks. With enzymes working as biological catalysts, your body can digest a full meal in just a few hours. This shows how vital enzymes are — they keep the speed of life-sustaining reactions at a level that actually keeps you alive.
Summary of enzyme characteristics:
| Feature | Detail |
|---|---|
| What they are | Proteins |
| Their role | Biological catalysts |
| What they do | Speed up metabolic reactions |
| Are they used up? | No — they remain unchanged after each reaction |
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