What is the role of proteins in the cell membrane?

Proteins in the cell membrane play a crucial role in transport and signaling, which is why this option is the correct choice. These membrane proteins can function as transport channels or carriers that facilitate the movement of substances across the membrane, allowing essential ions, nutrients, and molecules to enter and exit the cell. This function is vital for maintaining homeostasis and allowing the cell to respond to changes in its environment.

In addition to transport, these proteins also act as receptors that receive signals from hormones, neurotransmitters, and other signaling molecules. When these molecules bind to the proteins, they can initiate a response within the cell, leading to various physiological processes. This signaling capability is essential for communication between cells and coordinating complex biological functions.

While proteins can support cell shape and provide some structural integrity, this is more commonly a function of the cytoskeleton and other structural components. Similarly, energy provision is primarily the role of carbohydrates and fats within the cell, while protection against pathogens typically involves other mechanisms, such as the immune system or barriers formed by epithelial layers. Thus, the pivotal functions of membrane proteins in transport and signaling distinguish them as vital components of the cell membrane.