Problem 1
Match the terms with the descriptions. (a) Primary messenger (b) Second messenger (c) G-protein coupled receptor (d) Heterotrimeric G-protein (e) \(\mathbf{G}_{\alpha \mathrm{s}}\) (f) Protein kinase \(A\) (g) \(\overline{\text { cAMP }}\) phosphodiesterase (h) GTPase activity (i) Cholera (j) Pertussis (k) Phospholipase \(\mathrm{C}\) (l) \( G_{\alpha q}\) (m) Inositol trisphosphate (n) Protein kinase \(\mathrm{C}\) 1\. Activated by \(7 \mathrm{TM}\) receptor 2\. Stimulated by cAMP 3\. Results in the reassociation of \(G_{\alpha}\) and \(G_{\beta \gamma}\) 4\. Generates two second messengers 5\. Activated by diacylglycerol 6\. Composed of seven transmembrane helices 7\. Message received by the cell 8\. Results from \(G_{\text {ci }}\) inhibition 9\. Activates phospholipase \(\mathrm{C}\) 10 Activates adenylate cyclase 11\. Activates a \(\mathrm{Ca}^{2+}\)channel 12\. Due to persistent stimulation of \(G_{\alpha s}\) 13\. Intracellular chemical that relays message from ligand receptor complex 14\. Results in the inactivation of protein kinase A
Problem 2
What are the three major classes of membrane receptors?
Problem 3
Explain how a small number of hormones binding to the extracellular surface of a cell can have a large biochemical effect inside the cell.
Problem 4
What are some of the structural features common to all membrane-bound receptors?
Problem 5
Why is the GTPase activity of G proteins crucial to the proper functioning of a cell?
Problem 6
Hormones affect the biochemistry of a distinct set of tissues. What accounts for the tissue specificity of hormone action?
Problem 7
Match the terms with the descriptions. (a) Growth hormone binding (b) Growth hormone receptor (c) Receptor tyrosine kinase (d) Grb-2 (e) Sos (f) Ras (g) IRS (h) Phosphoinositide kinase 1 (i) \(\mathrm{PIP}_{3}\) -activated kinase (j) Akt 1\. Dimerization results in cross-phosphorylation 2\. Activates Ras 3\. Activates JAK 4\. Adaptor protein in insulin signaling pathway 5\. Activates Akt 6\. Binds IRS and forms \(\mathrm{IP}_{3}\) 7\. Causes receptor dimerization 8\. Promotes movement of glucose transporters to the cell membrane 9\. Small G-protein 10\. Binds receptor tyrosine kinase and Sos
Problem 8
In an elegant experiment on the nature of receptor tyrosine kinase signaling, a gene was synthesized that encoded a chimeric receptor-the extracellular part came from the insulin receptor, and the membranespanning and cytoplasmic parts came from the EGF receptor. The striking result was that the binding of insulin induced tyrosine kinase activity, as evidenced by rapid autophosphorylation. What does this result tell you about the signaling mechanisms of the EGF and insulin receptors?
Problem 9
An antibody has two identical antigen-binding sites. Remarkably, antibodies to the extracellular parts of growth-factor receptors often lead to the same cellular effects as does exposure to growth factors. Explain this observation.
Problem 10
What is the difference between heterotrimeric G proteins and small G proteins?
