The document describes the key parts and functions of cells. It discusses the cell membrane, nucleus, mitochondria, Golgi bodies, endoplasmic reticulum, ribosomes, vacuoles, lysosomes, centrioles, cytoplasm, chromatin, cilia, flagella, chloroplasts, cell walls, cytoskeleton, and plastids. For each part, it provides the location and basic functions, such as the cell membrane protects the cell and lets things in and out, the nucleus controls the cell, and mitochondria produce energy.