The cell membrane is selectively permeable.  Which type of membrane protein best illustrates this concept?

The type of membrane protein that best illustrates the concept of the cell membrane being selectively permeable is the transport protein.

Step 1: Understanding the question The question is asking for a type of protein that is found in the cell membrane and demonstrates the property of selective permeability.

Step 2: Understanding selective permeability Selective permeability is a property of cellular membranes that only allows certain molecules to enter or exit the cell. This regulation of substances in and out of the cell is crucial for the cell's survival and function.

Step 3: Identifying the protein Transport proteins are the type of proteins that best illustrate this concept. They are found in the cell membrane and regulate the movement of substances across the membrane.

Step 4: Understanding how transport proteins work Transport proteins allow specific molecules or ions to move through the cell membrane. They can either facilitate passive transport (where substances move along their concentration gradient without the use of energy) or active transport (where substances move against their concentration gradient, requiring energy).

So, the transport proteins in the cell membrane best illustrate the concept of selective permeability as they regulate and control the passage of molecules and ions in and out of the cell.