Enzymes Make the World Go 'Round

We often talk about reactions and the molecules that change in those reactions. Those changes don't happen on their own. If you leave a blob of protein in a Petri dish, will it just break down to the amino acids? No. What will do it? Enzymes! Enzymes are the biological substances (proteins) that act as catalysts and help complex reactions occur everywhere in life.

Assembly Line Robots

You all know about cars and the assembly lines where they are made. There are giant robots helping people do specific tasks. Some lift the whole cars, some lift doors, and some just put bolts on. Enzymes are like those giant robots. They grab one or two pieces, do something to them, and then release them. Once their job is done, they move to the next piece and do the same thing again. They are little protein robots inside your cells.

Enzymes complete very, very specific jobs and do nothing else. The robot that was designed to move a car door can't put brakes on the car. The specialized robot arms just can't do the job. Enzymes are the same. They can only work with specific molecules and only do specific tasks. For example, you might have a protein in a cell. Even with hundreds of amino acids in the chain, the overall shape changes if one amino acid is different. That tiny shape change could stop the enzyme from doing its job. Some herbicides are used to block enzyme activity. Plants have adapted by changing one or two amino acids in the enzymes. They can continue to work with the correct proteins and there is no bonding to the herbicides. In the same way that there are specialized robots for different types of cars, there are enzymes for neural cells, intestinal cells, and your saliva.

Substrate combines with active site

There are four steps in the process of an enzyme at work:
1. An enzyme and a substrate are in the same area. The substrate is the biological molecule that the enzyme will work on.
2. The enzyme grabs on to the substrate at a special area called the active site. Enzymes are very, very specific and don't just grab on to any molecule. The active site is a specially shaped area of the enzyme that fits around the substrate. The active site is like the grasping handle of the robot on the assembly line. It can only pick up one part.
3. A process called catalysis happens. Catalysis is when the substrate is changed. It could be broken down or combined with another molecule to make something new.
4. The enzyme lets go. This is a big deal. When the enzyme lets go, it returns to normal, ready to work on another molecule of substrate. The first molecule is no longer the same. It is now called the product.

Can You Stop Them?

Good question! We know what you're thinking: "What if enzymes just kept going and converted every molecule in the world? They would never stop. They would become monsters!" There are many factors that can regulate enzyme activity, including temperature, activators, pH levels, and inhibitors, which we will cover in the next section.

RELATED LINKS

- Biology4Kids: Scientific Method
- Biology4Kids: Cell Structure
- Geography4Kids: Carbon Cycle
- Geography4Kids: Biosphere

-	Overview
-	Metabolism
-	Cycles
-	Carbohydrates
-	Lipids
-	Nucleic Acids
-	DNA
-	Amino Acid Structure
-	20 Amino Acids
-	Proteins
>	Enzymes
-	Enz. Regulation
	MORE CHEMISTRY TOPICS

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