We often call life here on Earth carbon-based life because carbon is an essential component of the long-chain molecules needed for life, like proteins and DNA. However, it would also be accurate to call us phosphorus-based life since all life needs phosphorus to fulfill its energy needs. In biology, this energy is adenosine triphosphate (or ATP), which is utilized in catabolic and anabolic reactions. In the body, catabolic reactions break down larger molecules, like lipids, carbohydrates, and proteins, which we ingest from food. When larger molecules are broken down into smaller molecules, energy is released, and much of this energy is converted to ATP. The opposite happens in anabolic reactions; energy is needed to build larger molecules from smaller ones, so ATP is broken down. Two primary processes drive catabolic and anabolic reactions; these are dehydration synthesis and hydrolysis. In dehydration Synthesis, which is a type of anabolic reaction, new bonds are formed by removing water molecules. Two smaller molecules are joined covalently because the -OH from one molecule and the -H from another is removed, and they join together to form H2O, or as we know, water! Imagine you have two monomers: monomer 1 and monomer 2. When these molecules bind to create a dimer, one monomer loses a hydroxyl (or OH) group, and the other monomer loses a proton or an H, which then joins together to form water. If this process happens many times, the result is much longer chains called polymers. For example, plants use photosynthesis to create simple carbohydrates (or sugars) and then store them as starch. Starch is a polysaccharide (which is a large molecule made of many smaller monosaccharides). Another common example from plants is the production of maltose (or malt sugar). In this reaction, two glucose molecules combine to form maltose. Animals use dehydration synthesis to convert excess glucose (or small molecules) into glycogen (a longer molecule) for energy storage. For example, lactose is formed by combining glucose and galactose. Energy is released in this reaction due to the breaking down of chemical bonds. Dehydration synthesis, however, goes beyond carbohydrates. In amino acid dehydration synthesis, two amino acids combine to create a dipeptide and H2O. If this happens in many series of steps, then proteins are formed. The same is true for fats. Smaller fatty acids are combined to create longer-chain lipids. Now a word on hydrolysis. Hydrolysis is the reverse of a dehydration reaction and is an example of a catabolic reaction. In these reactions, longer polymers are broken down into smaller molecules by adding a water molecule. Let's look at cellulose, a vital molecule for plants which they use to build cell walls. While we humans can't digest cellulose, cows can because they've evolved to primarily eat grass. When cellulose is hydrolyzed, the bonds between the cellobiose and cellulase molecules are broken. The cellobiose molecule can then be broken down further by hydrolysis to create glucose for energy. In animals, hydrolysis is how we digest food into smaller units. For example, sucrose is a disaccharide you will recognize as table sugar. When sucrose is hydrolyzed, distinct monosaccharide sugars are created, like glucose and fructose. And that is it for our quick review on dehydration synthesis and hydrolysis. I hope you enjoyed this video. Please like if you want to see more of these review videos. Subscribe to this channel and hit the notification button if you do not want to miss a thing. I’ll see you next time.