questions

1. Briefly explain the location of the cellular receptor and the mechanism of action of steroid hormones. • Distinguish between synaptic, paracrine, and endocrine mechanisms of cell signaling. • Describe the structure and function of G-protein coupled receptors (GPCRs). • Describe the events by which receptor tyrosine kinases bring about a cellular response.

2. 1. You have identified a novel cytoplasmic protein. Sequence analysis revealed the presence of a number of potential serine/threonine amino acids that are potential phosphorylation sites. Based on this data, you hypothesize that this protein may be a substrate for a  A. protein kinase. B. receptor tyrosine kinase. C. G-protein-coupled receptor. D. ADP-ribosylase. 2. Why is phosphorylation-dephosphorylation commonly used to regulate signal transduction pathways?  A. Phosphate groups can be used as efficient second messengers. B. Protein kinases and phosphatases are abundant in most cells. C. The hydrolysis of bound GTP results in GDP and Pi. D. The addition or removal of a phosphate group can cause changes in a protein’s shape/function.  3. In a particular growth factor induced signal transduction pathway, which of the following proteins phosphorylates MAP kinase kinase?  A. MAP kinase B. MAP kinase kinase C. MAP kinase kinase kinase D. MAP phosphatase 

3. 1. You have identified a novel cytoplasmic protein. Sequence analysis revealed the presence of a number of potential serine/threonine amino acids that are potential phosphorylation sites. Based on this data, you hypothesize that this protein may be a substrate for a  A. protein kinase. B. receptor tyrosine kinase. C. G-protein-coupled receptor. D. ADP-ribosylase. 2. Why is phosphorylation-dephosphorylation commonly used to regulate signal transduction pathways?  A. Phosphate groups can be used as efficient second messengers. B. Protein kinases and phosphatases are abundant in most cells. C. The hydrolysis of bound GTP results in GDP and Pi. D. The addition or removal of a phosphate group can cause changes in a protein’s shape/function.  4. In a particular growth factor induced signal transduction pathway, which of the following proteins phosphorylates MAP kinase kinase?  A. MAP kinase B. MAP kinase kinase C. MAP kinase kinase kinase D. MAP phosphatase  . 4. The protein SOS is a guanine nucleotide exchange factor for Ras, a monomeric G Protein. SOS helps facilitate the exchange of GDP for GTP. What would be the effect of a mutation that inhibits the interaction between SOS and Ras?  A.  GTP would remain bound to Ras, thereby disrupting downstream signaling events. B.  GDP would remain bound to Ras, thereby disrupting downstream signaling events. C.  GTP would remain bound to Ras, leading to overstimulation of the Ras pathway. D.  GDP would remain bound to Ras, leading to overstimulation of the Ras pathway. 5. You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on. With which of the following types of cell extracts should you begin?  A. plasma membrane B. extracellular C. cytoplasmic D. nuclear 6. A mutation in the DNA binding domain of a steroid hormone receptor is most likely to affect the … …conformational change of the receptor. …binding of the hormone to the receptor. …translocation of the receptor to the nucleus. …cellular response to the hormone. 8. In response to a particular GPCR-mediated signaling event, if the enzymatic activity of the effector protein, phospholipase C, was blocked and failed to cleave phosphatidylinositol-4,5-bisphosphate (PIP2) into its two products (IP3 and DAG), which of the following signal transduction processes would most directly be affected?  A. the exchange of GDP for GTP on a G protein. B. the release of Ca++ from the endoplasmic reticulum. C. the GPCR binding to signal (ligand). D. the activation of protein kinase A by cAMP

4. 1. A team of researchers at a pesticide company are working produce a new rodent poison to address a growing problem of rat infestations at an old waterfront warehouse. The researchers are developing a poison that will cause the junctions between intestinal cells to break down. The poison will be incorporated into grain and left where the rodents will feed on it. Which of the following describes the most likely effect of this poison? A. The gap junctions will break down resulting in leaks in the digestive tract.B. The tight junctions will break down resulting in leaks in the digestive tract.C. The gap junctions will break down and interfere with absorption of nutrients.D. The tight junctions will break down and interfere with absorption of nutrients. 2. You have identified a novel cytoplasmic protein. Sequence analysis revealed the presence of a number of serine/threonine phosphorylation target motifs. Based on this data, you hypothesize that this protein may be a substrate for a A. protein kinase.B. receptor tyrosine kinase.C. G-protein-coupled receptor.D. phosphotyrosine adapter protein.

5. 4. An example of an effector protein whose activity can be indirectly modulated via a G protein coupled receptor isA. a receptor tyrosine kinase.B. glycogen synthase.C. adenyl cyclase.D. Ras.E. E2F.

6. 5. Which pair are examples of second messengers? A. Na+, K+B. serine, threonineC. estrogen, testosteroneD. glucose, glycogenE. cAMP, DAG 6. Which of the following statements best fits as an automobile analogy for a gut cell that has ingested the cholera toxin? A. The starter is broken.B. The gas pedal of a car is stuck when pushed down.C. The brake pedal of a car gets stuck while pushed down.D. The radio antenna is broken and does not receive signals.