1. Plasma membrane: This thin, flexible barrier encloses the cell, separating its internal environment from the external environment. It controls what enters and leaves the cell, ensuring the proper functioning of cellular processes.
2. Cytoplasm: This gel-like substance fills the cell and contains various organelles, the functional units of the cell. It also provides a medium for chemical reactions to occur.
3. DNA (deoxyribonucleic acid): This genetic material contains the instructions for the cell's structure and function. It is found in a region called the nucleoid in prokaryotic cells, and within a membrane-bound nucleus in eukaryotic cells.
These three structures are fundamental to the life of every cell, allowing it to maintain its integrity, carry out essential functions, and replicate.
