In this video, we're going to begin our introduction to metabolism. Metabolism is a term that refers to all of an organism's chemical reactions. When we talk about all of the chemical reactions inside an organism, that is what metabolism is referring to. Now, metabolic pathways are defined as a series of chemical reactions that ends up altering a substrate multiple times before the final product is released. Notice the example image below showing an example metabolic pathway.

Metabolic pathways have multiple steps. Notice that the very first substrate here, substrate A, is being converted into product B here by enzyme number 1, but notice that product B is not the final product. Instead, B is going to be converted into C by enzyme 2, and C is further going to be converted into D by enzyme 3, and then last but not least, D is going to be converted into E by enzyme 4. Here, it is molecule E that is acting as the final product of this pathway, and all these other molecules that we see here are acting as substrates to enzymes. We can see here that enzymes can work together in a series of steps to convert one substrate into another until the final product is released.

When enzymes work together in this fashion, we refer to it specifically as a metabolic pathway. There are two main types of metabolic pathways that you should be aware of, and we'll introduce those two in our next video. So I'll see you all there.