Cell structures are the various components that make up a cell, each with specific functions. The cell membrane surrounds the cell, controlling what enters and exits. Inside, the nucleus houses the cell's genetic material, while mitochondria produce energy. Other structures include ribosomes, which synthesize proteins, and endoplasmic reticulum, which helps in the production and transport of proteins and lipids. Different types of cells have unique structures tailored to their functions. For example, plant cells have a rigid cell wall for support and chloroplasts for photosynthesis, while animal cells lack these features but have more flexible shapes. Understanding these structures is essential for studying biology.