Bacterial cells are prokaryotic, meaning they lack a nucleus and membrane-bound organelles. Their structure typically includes a cell wall, which provides shape and protection, and a plasma membrane that regulates the movement of substances in and out of the cell. Inside, they contain cytoplasm, ribosomes for protein synthesis, and a single circular DNA molecule that carries genetic information. Many bacteria also have additional features, such as flagella for movement and pili for attachment to surfaces. The cell wall is primarily composed of peptidoglycan, which is crucial for maintaining the integrity of the cell. Bacterial cells can vary in shape, including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral).