Animal and plant cells are eukaryotic: their genetic material is inside a nucleus. Bacterial cells are prokaryotic and have no nucleus. Every structure inside a cell, called a sub-cellular structure, has a job to do.
Animal cells have a nucleus that contains the genetic material and controls the cell's activities, a cell membrane that controls what enters and leaves the cell, cytoplasm where chemical reactions happen, mitochondria where aerobic respiration releases energy, and ribosomes where proteins are made.
Plant cells have all of these structures and also have a cell wall made of cellulose, which strengthens the cell, chloroplasts, which contain chlorophyll and carry out photosynthesis, and a permanent vacuole full of cell sap, which keeps the cell firm.
Bacterial cells have a cell membrane, cytoplasm and ribosomes, and usually a cell wall as well. Their genetic material is chromosomal DNA, a single loop lying free in the cytoplasm. Many also have plasmid DNA, which is made of small extra rings. Many bacteria have a flagellum (plural flagella), a long whip-like tail that rotates to move the cell.
