What is "which part of the cell is semipermeable?

The part of the cell that is semipermeable is the cell membrane, also known as the plasma membrane. This phospholipid bilayer surrounds the cell and separates it from its external environment. The cell membrane is selectively permeable, meaning it allows certain substances to pass through while blocking others. Small, nonpolar molecules such as oxygen and carbon dioxide can freely pass through the cell membrane, while larger molecules and charged particles require the assistance of transport proteins to enter or exit the cell. This selective permeability helps the cell maintain its internal environment and carry out essential functions like nutrient uptake and waste removal.