a. ras that cannot hydrolyze GTP b. ras that cannot bind to gtp c. ras that cannot bind to grb2 or Sos d. ras that cannot bind to raf 答:a 18. The sequence of events that occurs after insulin binds to its receptor tyrosine kinase is a. binding ofIrs-> phosphorylation of proteins with SH2 domains-> effect b. binding of proteins with SH2 domains -> phosphorylation of Irs-> effect c. autophosphorylation and phosphorylation ofIrs-> binding of proteins with sh2 domains-> effect d. autophosphorylation and bind ing of IrS -> phosphorylation of proteins with sh2 domains -> effect 19.下列连接方式中属于与中间纤维相连的锚定连接的是(C)。 a.粘合带;b.粘合斑 桥粒 d.紧密连接。 20.缬氨霉素是一种可形成通道的离子载体,能够使(a)的运输速度提 高100000倍。 aK+ b Na+. C Ca2+. dH+ 四、简答题(毎题4分,选做5题,共20分) 1. Describe the similarities and differences in the cycling of Gs and Ras between the active and inactive forms Answer 1: Binding of hormone to its receptor causes a con-formational change eptor. The receptor then binds to gm protein causing a conformational change in the Gsa protein and release of the bound GDP. GTP then binds to Gsa which causes release of the GTP-Gsa complex from the B and r subunits. The gtp-g then activates adenylyl cyclase. Activation is short-lived because the intrinisic GTPase activity in Gsa hydrolyzes gtP to gdp and returns g to its inactive form 2.如何理解“被动运输是减少细胞与周围环境的差别而主动运输则是努 力创造差别维持生命的活力 答:主要是从创造差异对细胞生命活动的意义方面来理解这一说法。主动8 a. ras that cannot hydrolyze GTP b. ras that cannot bind to GTP c. ras that cannot bind to Grb2 or Sos d. ras that cannot bind to Raf 答:a 18. The sequence of events that occurs after insulin binds to its receptor tyrosine kinase is: a. binding of IRS -> phosphorylation of proteins with SH2 domains -> effect b. binding of proteins with SH2 domains -> phosphorylation of IRS -> effect c. autophosphorylation and phosphorylation of IRS -> binding of proteins with SH2 domains -> effect d. autophosphorylation and binding of IRS -> phosphorylation of proteins with SH2 domains -> effect 19. 下列连接方式中属于与中间纤维相连的锚定连接的是( c )。 a．粘合带； b．粘合斑； c．桥粒； d．紧密连接。 20. 缬氨霉素是一种可形成通道的离子载体, 能够使( a )的运输速度提 高 100,000 倍。 a.K+ ; b.Na+ ; c.Ca2+ ; d.H+ 四、简答题(每题 4 分， 选做 5 题，共 20 分) 1．Describe the similarities and differences in the cycling of Gs and Ras between the active and inactive forms. Answer 1:. Binding of hormone to its receptor causes a con-formational change in the receptor. The receptor then binds to Gm protein causing a conformational change in the Gs protein and release of the bound GDP. GTP then binds to Gs which causes release of the GTP-Gs complex from the  and  subunits. The GTP-Gs complex then activates adenylyl cyclase. Activation is short-lived because the intrinisic GTPase activity in Gs hydrolyzes GTP to GDP and returns G~ to its inactive form. 2. 如何理解“被动运输是减少细胞与周围环境的差别,而主动运输则是努 力创造差别,维持生命的活力”? 答: 主要是从创造差异对细胞生命活动的意义方面来理解这一说法。主动