AP BIOLOGY

Detailed explanation-1: -Amplification in signal transduction pathways. The activation of a single receptor by a signaling molecule, such as the neurotransmitter norepinephrine, can lead to the activation of numerous G-proteins inside cells.

Detailed explanation-2: -The molecules that relay a signal are often proteins. However, non-protein molecules like ions and phospholipids can also play important roles.

Detailed explanation-3: -The process of transduction involves an amplification of the original signal that allows the cell to quickly activate many molecules using fewer steps. The proteins activated in a signaling cascade are often kinases, proteins that add phosphate groups to other molecules, called phosphorylation.

Detailed explanation-4: -The process by which a cell responds to substances outside the cell through signaling molecules found on the surface of and inside the cell.