《生物化学》课程PPT教学课件（英文版）Chapter 13 Biosignaling

Chapter 13 Biosignaling

Chapter 13 Biosignaling

table13-1 Some Signals to Which Cells Respond Antigens Cell surface glycoproteins/oligosaccharides Developmental signals Extracellular matrix components Growth factors Hormones Light Mechanical touch Neurotransmitters Odorants Pheromones Tastants

(a) Specificity Signal molecule fits binding site on its complementary receptor other signals do not fit. Re eceptor Effect

(b) Amplification When enzymes activate Signal enzymes, the number of affected molecules increases geometrically in an enzyme cascade Enzyme 1 Enzyme 2 2 2 E enzyme 333333333

Signal (c) Desensitization/Adaptation Receptor activation triggers a feedback circuit that shuts off the receptor or removes AReceptor it from the cell surface Response

(d) Integration When two signals have Signal 1 Signal 2 opposite effects on a metabolic characteristic such as the concentration of a second messenger X Receptor/Receptor or the membrane potential 2 Vm, the regulatory outcome results from the integrated input from both receptors. TIX] or TV l[X] or lV Ne△x]orVm Response

Total binding doc Specific binding Nonspecific binding Total hormone added, [L]+RLI (a)

Slope Kd B max Bound hormone, IRL (b)

Gated ion channel Serpentine reeeptor Opens or clases in External ligand binding response to concentration to receptor (R) activates an of signal ligand (S) intracellular gtP- binding or membrane potential protein(G), which regulates an enzyme(Enz) that generates an intracellular Ion second messenger, X R Plasma Receptor enzyme membrane Ligand binding to extracellular domain stimulates enzyme activity in intracellular Steroid receptor DNA Steroid binding to a nuclear receptor protein allows the mRNA receptor to regulat Nuclear the expression of envelope Protein specific genes

The electrogenic Na*K ATPase establishes the membrane potential Na*K+ ATPase 十 P+P 2K INa high Lo [K+ high ICa2+] Higl Icl]High如 Lo Ions tend to move down their electrochemical gradient across the polarized membrane