Explain why an orphan receptor, once adopted, has low affinity for lipids.

Orphan receptors are a type of receptor that have not yet been identified or characterized in terms of their ligands or signaling pathways. When an orphan receptor is "adopted" and its ligands and signaling pathways are discovered, it may have low affinity for lipids because it was not originally designed to interact with lipid molecules.

Orphan receptors are typically proteins that are embedded in the cell membrane and are involved in signal transduction pathways. These receptors are usually specific to certain ligands, such as hormones or neurotransmitters, and are designed to bind to these ligands to initiate a cellular response.

When an orphan receptor is discovered to have a low affinity for lipids, it suggests that its natural ligands are not lipid molecules. Instead, the receptor may be more specialized to interact with other types of molecules, such as proteins or small molecules. This low affinity for lipids may be due to the specific structure and binding sites of the receptor, which are optimized for interactions with its natural ligands rather than lipids.

Overall, the low affinity of an adopted orphan receptor for lipids is likely a result of its specific evolutionary design and function in the cell signaling pathways.

An orphan receptor is a nuclear receptor that does not have a known ligand. Once an orphan receptor is adopted by a ligand, it undergoes a conformational change that results in a decrease in its affinity for lipids. This is because the ligand binds to the receptor in a way that prevents it from interacting with lipids. As a result, the adopted orphan receptor is less likely to be localized to the lipid bilayer and more likely to be found in the nucleus, where it can regulate gene transcription.