Question

Membrane proteins are among the most important proteins biologically because they allow cells to communicate with their environments. In humans, they determine whether the immune system recognizes the cell as foreign or not and they are the targets of most pharmaceuticals. In all organisms, membrane proteins are responsible for other functions as well. One function determines when and if cell division takes place. That is

Answer 1

Membrane proteins are crucial for various cellular functions, including molecule transport, cell signaling, and immune responses, with integral and peripheral types interacting with the cell membrane differently.

Step-by-step explanation:

Membrane proteins serve critical roles in the function of cells by regulating the passage of molecules and ions, enabling cell-cell communication, and acting as receptors for signaling molecules. Integral membrane proteins are firmly embedded within the plasma membrane and are essential for transporting substances across this barrier. Another class is peripheral proteins, which interact more loosely with the membrane's surfaces.

These proteins participate in a wide array of cellular processes including cell signaling, molecular transport, and enzymatic activity. The extracellular domains of membrane proteins are often glycosylated, playing a part in cell recognition and immune response, while the cytoplasmic parts may interface with components of the cytoskeleton. The diversity of membrane proteins enables them to function as receptors for hormones or neurotransmitters, to facilitate cell adhesion, and to anchor cells to extracellular matrices.

Answer 2

One function determines when and if cell division takes place. That is activation of growth hormones.
When these hormones start forming, that is when the cell is going to be divided.