Hydrogen bonds are important in many living organisms. They allow bonds between biomolecules that can be created and broken with control to allow life to proceed. For example, DNA that codes our genes contains two strands that are connected by many hydrogen bonds, like a zipper closing. Because the hydrogen bonds are not very strong, the two strands can later be "unzipped" and separated in order to read or copy the DNA. In protein molecules, intramolecular hydrogen bonds hold the protein molecule together in the shape that is needed. Intermolecular hydrogen bonds help connect protein molecules to each other to make many structures important for life, such as ribosomes that create new proteins. 