What structure within the cell is associated with cell adhesion and signaling?

The plasma membrane is essential for cell adhesion and signaling due to its composition and function. It is a dynamic barrier that separates the intracellular environment from the extracellular space and is rich in various proteins that play key roles in these processes.

Cell adhesion molecules, which are found in the plasma membrane, facilitate the attachment of cells to one another and the extracellular matrix. This adhesion is critical for tissue integrity, communication, and the overall structural organization of tissues in multicellular organisms.

Moreover, the plasma membrane is involved in signaling by housing receptors that can detect external signals such as hormones, growth factors, and other signaling molecules. Upon binding of these ligands, these receptors can initiate intracellular signaling cascades that influence cellular responses, including growth, differentiation, and apoptosis.

In contrast, other organelles listed do not have the same functions regarding cell adhesion and signaling. The nucleus primarily houses genetic material and regulates gene expression but is not directly responsible for adhesion. Mitochondria are involved in energy production and metabolic processes while ribosomes focus on protein synthesis, neither of which are directly related to adhesion or signaling functions.