AP BIOLOGY

Detailed explanation-1: -A ligand is a molecule that binds another specific molecule, in some cases, delivering a signal in the process. Ligands can thus be thought of as signaling molecules. Ligands interact with proteins in target cells, which are cells that are affected by chemical signals; these proteins are also called receptors.

Detailed explanation-2: -The ligand is a chemical messenger released by one cell to signal either itself or a different cell. The binding results in a cellular effect, which manifests as any number of changes in that cell, including altering gene transcription or translation or changing cell morphology.

Detailed explanation-3: -As already noted, all signaling molecules act by binding to receptors expressed by their target cells. In many cases, these receptors are expressed on the target cell surface, but some receptors are intracellular proteins located in the cytosol or the nucleus.

Detailed explanation-4: -Cell-surface receptors. Cell-surface receptors are membrane-anchored proteins that bind to ligands on the outside surface of the cell.

Detailed explanation-5: -Transduction: When the signaling molecule binds the receptor it changes the receptor protein in some way. This change initiates the process of transduction. Signal transduction is usually a pathway of several steps. Each relay molecule in the signal transduction pathway changes the next molecule in the pathway.