Enzymes are proteins inside the cells. They are formed by special chains of amino acids that come together in different shapes to do special jobs, like breaking down sugar and fat molecules or to make more enzymes. The cells need the enzymes to live, and each different enzyme has its own work to do. When the body is missing a type of enzyme, the cells can't work properly. This can lead to problems for the person whose body is missing the enzymes.
An enzyme is a kind of big, complicated protein molecule, made mainly of hydrogen and carbon atoms, but with some other atoms as well. Both prokaryote and eukaryote cells use enzymes (ENN-zimes), so the first enzymes probably evolved around four billion years ago, together with the first living cells.
Prokaryote cells assemble enzymes in their cytoplasm. The cell's DNA molecule uses enzymes to assemble RNA molecules, and these RNA molecules then in turn assemble more kinds of enzymes. The cell pushes some of these enzymes outside the cell to digest food by breaking it apart into smaller pieces that can get through the cell membrane. Other enzymes can digest smaller molecules floating in the cytoplasm inside the cell. Some enzymes grab two small molecules and attach them together to make a larger molecule, like a lipid to fix the cell membrane. When the enzyme is done, it lets the new molecule go, and it's ready to grab two more molecules and do it again. Each kind of enzyme has its own shape, and it will only work with molecules that fit into it exactly, like having the right puzzle piece in a puzzle, or the right key for a lock. That way each kind of enzyme can do its job and not interfere with anything else in the cell.
Eukaryote cells make enzymes in the endoplasmic reticulum, following instructions from the cell's RNA. Then those enzymes, in turn, build more enzymes, and the enzymes float out of the endoplasmic reticulum into the Golgi bodies and then into the lysosomes, where they break down large molecules of food or garbage, or into vacuoles, or into the…