AP Bio Unit 4: Cell Communication and Cell Cycle Cheat Sheet (DRAFT) by PrincessB3ll3

Function: results in changes in gene expression and cell function, which may alter phenotype or result in programmed cell death (apopt­osis)

1. Recogn­ition of a chemical messenger (ligand) by a receptor protein in a target cell
-Ligan­d-b­inding domain of receptor recognizes ligand (peptide, small chemical, or protein) in a specific one-to-one relati­onship.
-Ex: G protei­n-c­oupled receptors in eukaryotes

2. Signaling cascades relay signals from receptors to cell targets
-Often amplify incoming signals
-Results in cell growth, secretion of molecules, or gene expression

3. After ligand binds intrac­ellular domain of a receptor protein changes shape, initiating signal transd­uction
-Second messen­gers: Molecules that relay and amplify the intrac­ellular signal (ex: cyclic AMP)
-Binding of ligand to ligand­-gated channels can cause channel to open or close

Changes that alter cellular response:
-Mutations in any domain of receptor protein or component of signaling pathway may affect succeeding components
-Chemicals that interfere with any component of the signaling pathway may activate or inhibit the pathway

Negative:
-Maintain homeos­tasis for a particular condition by regulating physio­logical processes
-If system disrupted, negative feedback mechanisms return system to target set point
-Operate on molecular and cellular level

Positive:
-Amplify responses and processes in biological organisms
-If system disrupted, positive feedback mechanism moves farther from set point
-Ampli­fic­ation: stimulus is further activated, initiates an additional response that produces system change