Question

1) How does polarity play a role a role in receptor affinity?

2) Is a polar or nonpolar molecule more likely to bind to a Beta 2 receptor?

Answer 1

1)Polarity play a role a role in receptor affinity as: Ligand bind to the receptors. The receptor can be present on the cell surface or intracellularly.

• Polar ligands (water soluble ligands) are charged and so cannot cross the plasma membrane. So, most polar ligands bind to the extracellular or cell-surface receptors, staying on the outer surface of the cell.
• Intracellular receptors: They are located in the cytoplasm of the cell and are activated by non- polar ligand molecules which are able to pass through the plasma membrane.
• Cell-surface receptors: They bind to an external ligand molecule and convert an extracellular signal into an intracellular signal.
• Gprotein-coupled receptors (GPCRs):They are a type of cell surface receptors that have a common method of signaling. GPCRs have seven different protein segments that cross the membrane, and they transmit signals inside the cell through a protein called a G protein.

2)Beta 2 receptor ​​​​​- A G protein coupled receptor.

Beta-2 adrenergic receptor (β2 adrenoreceptor) belong to G protein coupled receptor, a type of cell membrane surface receptor that interacts with epinephrine, a hormone and ligand.

The polarity of the epinephrine molecule allows it to bind to a stimulatory G protein which is coupled to Beta-adrenergenic receptors

So, polar molecule (mainly epinephrine) are more likely to bind on a Beta 2 receptor.