Final answer:
The plasma membrane is a selectively permeable structure that regulates the entry and exit of substances into and out of the cell, essential for maintaining cell viability and function.
Step-by-step explanation:
The structure referred to as a screen that allows certain substances to pass through into the cell while others cannot is the plasma membrane. The plasma membrane is selectively permeable, meaning it allows some substances to pass through but not others. This characteristic is vital for a cell's survival as it maintains a balance of materials, allowing the cell to sustain itself. The plasma membrane facilitates the transport of materials necessary for cell function, sometimes utilizing mechanisms that require energy, such as the hydrolysis of adenosine triphosphate (ATP). Additionally, it is involved in maintaining an imbalance of sodium and potassium ions, which is crucial for cellular processes.