There's an old saying, "You are what you eat." In some senses, this is literally true! When we eat food, we take in the large biological molecules found in the food, including carbohydrates, proteins, lipids (such as fats), and nucleic acids (such as DNA), and use them to power our cells and build our bodies. Review the different types of macromolecules and what they are made up of.
Where would we be without water? Well, we probably wouldn't exist at all! Review the properties of water including its hydrogen bonding, and learn why it's a key ingredient for biological systems of all sizes.