AP BIOLOGY

Detailed explanation-1: -Second messengers are small molecules and ions that relay signals received by cell-surface receptors to effector proteins.

Detailed explanation-2: -Because membrane receptors interact with both extracellular signals and molecules within the cell, they permit signaling molecules to affect cell function without actually entering the cell.

Detailed explanation-3: -Paracrine signaling Often, cells that are near one another communicate through the release of chemical messengers (ligands that can diffuse through the space between the cells). This type of signaling, in which cells communicate over relatively short distances, is known as paracrine signaling.

Detailed explanation-4: -In which type of signaling, the cell that expresses messenger molecules also produces receptors? Explanation: In autocrine signaling, the cells that express messenger molecules also synthesize surface receptors. Surface receptors can respond to the messengers synthesized by the cell itself.