AP BIOLOGY

Detailed explanation-1: -When a ligand (the paracrine factor) binds its receptor in the extracellular region, the ligand induces a conformational change in the receptor’s structure. This shape change is transmitted through the membrane and changes the shape of the cytoplasmic domains.

Detailed explanation-2: -Signal transduction occurs as a result of a ligand binding to the outside region of the receptor (the ligand does not pass through the membrane). Ligand-receptor binding induces a change in the conformation of the inside part of the receptor, a process sometimes called “receptor activation".

Detailed explanation-3: -Cellular receptors are proteins either inside a cell or on its surface which receive a signal. In normal physiology, this is a chemical signal where a protein-ligand binds a protein receptor. The ligand is a chemical messenger released by one cell to signal either itself or a different cell.

Detailed explanation-4: -Changes in signal transduction pathways alter cellular response by altering the protein and enzyme synthesis, thereby affecting processes like binding messenger molecules to the receptor.