Enzymes are the catalysts of living cells. If science learning requires an understanding of basic concepts, the function of enzymes in a chemical reaction is surely one of these important concepts. Here's a short video to show you what enzymes can do for you:
Thousands of chemical reactions every second form a complex web that keeps an organism alive. Even though many of these chemical reactions are exergonic (which means they release energy), they still need a bit of energy input in order to start.
For example, think of the energy of combustion, more commonly known as fire. (Science learning may have started with fire, long ago!) Once you have a good fire going, you can throw on as many logs as you want, and they will burn. The reaction will be exergonic--you'll get light and heat as each log combusts. However, logs usually don't start burning spontaneously by themselves. You need matches to get the fire going. The match provides the energy to start a fire. Once you start your fire, it will keep on burning as long as you provide fuel, oxygen, and the right conditions.
It's the same in many chemical reactions that take place in cells. For example, when an organism hydrolyzes sugar, there is a net release of energy which can be used to convert ADP into ATP. However the organism needs a bit of energy to start the reaction. This is known as the Activation Energy.
In general, it's not a problem to provide activation energy (we wouldn't be here if it were!). But an organism can function more efficiently if there is a way to reduce the amount of activation energy needed. That's where the enzymes come in handy.
Enzymes are macromolecules (typically protein but sometimes special RNA) that assist in a chemical reaction. A specific enzyme will work for a specific chemical in a specific reaction. The chemicals impacted by the enzyme are called substrates.
Unlike the substrate, the enzyme itself will not change or be used up in the reaction. This means it's available for more reactions in the future. Some reactions take place many times per second, in multiple locations, inside millions of cells. Without the use of enzymes, organisms would be a lot slower, weaker, and less efficient. Be glad you have enzymes.