The cell is the basic structural, functional, and biological unit of all known living organisms. The cells have been classified into two categories: Prokaryotic cells and Eukaryotic cells. The cell is the fundamental structural and functional unit of all living organisms. The cell wall is found in plant cells and made of cellulose, hemicellulose, pectins, and d proteins. This is the outermost boundary of plant cells, which gives shape to the cell and protects the cell from mechanical damage. Within plant cells, chloroplasts are responsible for trapping light energy essential for photosynthesis. A cell is the smallest unit of life. Cells are often called the "building blocks of life".