In this video, we're going to introduce two different types of chemical reactions. Chemical reactions are going to be categorized into two groups based on their energy requirement. Those two groups are going to be listed down below, and we also have two images down below to show those two different groups of chemical reactions.
The very first group is going to be endergonic reactions, which require an input of energy. You can think the 'en' in endergonic reactions is for the 'en' in entering the reaction because energy needs to enter the reaction for endergonic reactions to occur. Just like this person here is entering into the room, you can think that endergonic reactions require energy to enter the reaction. You can see the little symbol here on his shirt represents energy, and so the person coming into the room represents energy entering the reaction.
The second type of reaction that you all should know are exergonic reactions, which are practically the opposite of endergonic reactions. Instead of requiring an input of energy, they actually release energy into the environment. Exergonic reactions allow energy to exit the reaction. You can think the 'EX' in exergonic reaction is for the 'EX' in exit the reaction. It's just like this person here is exiting the room through this door right here. You can see the little energy symbol on his shirt, so that he's representing energy and he's exiting the room.
Let's take a look at our example down below to better understand the difference between endergonic and exergonic reactions. Notice that our image is broken up into two halves, on the left hand side over here what we're showing you are the endergonic larger and more structured molecules. When you take a look at our image down below, notice that it's showing the building blocks, the broken-down building blocks over here on the left hand side as the reactants, the starting material or the ingredients for the reaction. By the end of the reaction, notice that those starting materials have been built up into a larger, more complex structure here that is more organized. This would be the product over here, and there is some building-up occurring here in this endergonic reaction. Because it's an endergonic reaction, you can see that energy has to enter this system. You can see the entering person here and the energy coming into the chemical reaction.
If we take a look at the little graph that we have down below, this little plot, notice that it has a y-axis that has potential energy increasing from the bottom to the top and it also has the progress of the reaction on the bottom. Notice that we start off with the reactants over here on the left hand side and the reactants have lower energy, here in comparison to the products over here, which notice they have higher energy since it's a higher bar. So they have higher energy. The reason that the products have higher energy is because energy is entering the system here. It's entering into the products. Energy is required for endergonic reactions and for building up larger molecules.
On the right hand side over here what we're showing you is the complete opposite. We're showing you exergonic reactions, which are going to be used to break down substances into their smaller components. Notice that this time we're starting the reaction with reactants that are larger, more complex, and built-up. Then notice that by the end of the reaction, the molecules are being broken down into their smaller individual components. In this exergonic reaction, notice that energy is actually leaving the system. It is exiting the system. You can think the 'EX' in exergonic is for energy exiting the system.
When we take a look at the graph down below, notice that the reactants this time have higher energy than the products, which are over here. Notice the products over here, they have lower energy. Because the products have lower energy, it means that the energy is exiting the system. It's leaving the system and going into the environment. Energy is being released into the environment due to this difference in energy where the reactants are higher and the products are lower energy.
You can see how endergonic and exergonic reactions are practically the opposite of each other. The cell can utilize both endergonic and exergonic reactions, and we'll be able to talk even more about these reactions as we move forward through our course. But for now, this concludes our introduction to endergonic and exergonic reactions, and I'll see you all in our next video.
