CHEN 2810
Homework #4
Due 2/25/14

To receive credit for completing this assignment you must submit your answers to the questions below on the provided answer sheet. The answer sheet should be submitted with your name on it electronically to drop-box on the D2L website. No credit will be given for completing the HW assignment if the provided answer sheet is not used and if it is not submitted via drop-box.

Part 1:

1) ______BD________ | 2) ____C__________ | 3) ______A_______ |

Part 2:

4) ____cAMP_+ppi_________ | 5) ___PIP2___________ | |

Part 3:

6) There will not be a phosphorylated protein or relay protein and there will not be a cellular response at all. | 7) If it is coupled than the proteins can be turned on and off easily and only when it is needed. When the RAS protein is mutated, it can lead to cancer because the RAS protein can't be turn off. | 8)The advantage of the system is that since every next step is only activated by the previous step, than nothing unnecessary is produced. The disadvantage is that is one of the steps(proteins) can't be activated than nothing will be produced or if a protein is mutated but still functional(just can't be turned off) than there will be an over production and that is not good for the cell or body. | 9) 2,097,152,000 cells | 10) The G2/M phase checkpoint |

Part 1: Multiple Choice

1) Which of the following events occurs following the binding of a ligand to a G protein-coupled receptor that triggers release of Ca2+? (Note: more than one of the following answers is correct. Select all that apply.)

a. Activation of protein kinase A by IP3 b. Phospholipase cleavage of PIP2 to IP3 and DAG c. Release of DAG into the cytosol d. IP3-mediated opening of calcium channels in the ER membrane

2) If two chromosomes are homologous, they

a. Look similar under the microscope. b. Have very similar DNA sequences. c. Carry the same types of genes. d. May carry different versions of the same gene. e. Are all of the above.

3) Which statement best explains the way that an abnormal p53 causes normal cells to become cancer cells?

a. The abnormal p53 protein fails to carry out DNA repair. b. The abnormal p53 protein triggers too many cells to grow. c. The abnormal p53 protein damages the normal DNA. d. The abnormal p53 protein stimulates the death of normal cells. e. The abnormal p53 protein enhances tumor-suppressor genes.

Part 2: Structures

Identify each of the two structures below.

4) Structure 1:

5) Structure 2:

Part 3: Short Answer

6) In normal cells an RTK receptor that binds to epidermal growth factor is present. When EGF is present in the extracellular space it binds to the receptor and initiates an RTK signal transduction cascade that ultimately tells the cell to undergo mitosis. Describe what would happen to cell division if a cell begins to express both the natural EGF receptor and a mutated version that is capable of binding to EGF. While both receptors can bind to EGF the mutated version cannot initiate receptor dimerization and autophosphorylation.

7) Why is it beneficial for a cell signaling pathway to be coupled to a MAP kinase cascade which essentially activates a number of MAP kinase proteins via phosphorylation? 8) Kinase cascade proteins need to act sequentially in order to be effective. How does the cell help to ensure that these reactions take place in the correct order, despite occurring in a large volume of reaction space in the cytoplasm? What are the advantage(s) and disadvantage(s) to this method of reaction organization?

9) Initially, you place 1000 cells in a culture dish. After 21 divisions, how many cells would you expect there to be in the dish?

10) A new chemical is derived that hinders the formation of MPF, thereby inhibiting the formation of this kinase-cyclin complex. Identify which checkpoint within eukaryotic cell cycle would be affected by this chemical’s inhibitory action and explain the result.