AP BIOLOGY

Detailed explanation-1: -Moreover, because cell surface receptors can often bind a number of different ligands there is a pertinent need to image individual receptors distributed in cellular membranes and to simultaneously quantify their interaction with several ligands.

Detailed explanation-2: -The binding can be specific and reversible. A ligand may activate or inactivate a receptor; activation may increase or decrease a particular cell function. Each ligand may interact with multiple receptor subtypes. Few if any drugs are absolutely specific for one receptor or subtype, but most have relative selectivity.

Detailed explanation-3: -The same ligand can cause different responses in different cell types due to differences in protein expression in the different cells, where the same signal activates different signaling pathways, leading to a different response in each cell type.

Detailed explanation-4: -Ligands that can enter the cell Small, hydrophobic ligands can pass through the plasma membrane and bind to intracellular receptors in the nucleus or cytoplasm. In the human body, some of the most important ligands of this type are the steroid hormones.