DNA helicase is the enzyme that unwinds the strands of DNA. It is a motor protein and "unzips" the DNA molecule by using the free energy of ATP to break the hydrogen bonds between the nucleotides of the DNA molecule that hold it together. There are many types of helicase that are used in multiple ways by the cell, and DNA helicase is found in many types of cells including both prokaryotic and eukaryotic cells. DNA helicase, along with all the other helicases is an enzyme. This isindicated in the name by the "ase" ending. All enzymes are proteins. Protein synthesis occurs in the ribosomes of the cell, either floating free in the cytoplasm, or attached to the rough ER.