Cell Membrane: A cell membrane works like a screen. It lets the good things in like nutrients and lets the bad things out like waste. It is like a sieve.Cytoplasm: Cytoplasm is the jelly-like part of the cell where the action takes place. It is where the nutrients are used.Nucleus: The nucleus is the brain of the cell. It controls the cell, and tells it what to do. The nucleus also contains the DNA which is like a blueprint. A blueprint is a plan that people use when they build. A cell's blueprint is the plan the cell uses when it reproduces.