The Ras protein functions as a molecular switch that is set to its onstate by a guanine-nucleotide exchange factor (GEF) that causes it to bind GTP. A GTPase-activating protein (GAP) resets the switch to the off state by inducing Ras to hydrolyze its bound GTP to GDP much more rapidly than in the absence of the GAP. Thus Ras works like a light switch that one person turns on and another turns off. In a cell line that lacks the Ras-specific GAP, what abnormalities would you expect to find in the way Ras activity responds to extracellular signals

问答题简述第二信使cAMP的发现及生成的实验证明(20分)。

问答题Why do you suppose that phosphorylation dephosphorylation, plays such a prominent role in switching proteins on and off in signaling pathways

问答题Describe the different methods that cells use to restrict proteins tospecific regions of the plasma membrane. Is a membrane with many anchored proteins still fluid

问答题How is an IP3-triggered Ca2+ response terminated

问答题Why does a red blood cell membrane need proteins

问答题Should RGS (regulator of G protein signaling) proteins be classified as GEFs (guanine nucleotide exchange factors) or GAPs (GTPase activating proteins) Explain what role this activity plays in modulating G-protein-mediated responses in animals and yeasts.

问答题Transport by carrier proteins can be either active or passive, whereas transport by channel proteins is always passive. Explain your answer.

问答题The signaling mechanisms used by a steroid-hormone(固醇激素) receptor and by an ion-channel-linked receptor have very few components(组分). Can either mechanism lead to an amplification of the initial signal If so, how

问答题The basic structure of biological membranes is determined by the lipid bilayer, but their specific functions are carried out largely by proteins. Explain your answer.

判断题电镜的波长与电压有关，电压越高，波长越短，分辨率越高。