The organelle that controls the exchange of materials between a cell and its environment is the cell membrane (also called the plasma membrane).

Here's why:

* Selective Permeability: The cell membrane is selectively permeable, meaning it allows some substances to pass through while blocking others. This allows the cell to maintain a stable internal environment.

* Transport Mechanisms: The cell membrane utilizes various transport mechanisms, including:

* Passive Transport: Diffusion, osmosis, and facilitated diffusion, which don't require energy, move substances down their concentration gradient.

* Active Transport: Requires energy to move substances against their concentration gradient.

* Protection: The cell membrane provides a protective barrier, shielding the cell's internal contents from the external environment.

While other organelles like the vacuole and endoplasmic reticulum play roles in storage and transportation within the cell, the cell membrane is the primary gatekeeper for the exchange of materials between the cell and its surroundings.