Question

explain the terms ligand and receptor. where are the two different locations that receptors are found and what type of ligand do each bond with? why can't all receptros be inside the cell?

Answer 1

Receptors are protein molecules that bind to ligands. There are two types: internal receptors found in the cytoplasm and cell-surface receptors located on the external surface of the cell membrane.

Step-by-step explanation:

Receptors are protein molecules in the target cell or on its surface that bind to ligands. There are two types of receptors:

1. Internal receptors: Also known as intracellular or cytoplasmic receptors, they are found in the cytoplasm of target cells. They respond to hydrophobic ligand molecules that can pass through the plasma membrane. These receptors predominantly mediate gene expression by binding to proteins that regulate mRNA synthesis (transcription).
2. Cell-surface receptors: These receptors are located on the external surface of the cell membrane. They have three main components: an external ligand-binding domain, a hydrophobic membrane-spanning region, and an intracellular domain inside the cell. Ligands that cannot pass through the plasma membrane, such as water-soluble hydrophilic ligands, bind to cell-surface receptors to transmit signals to the inside of the cell.