1. Why do polysaccharides have greater structural diversity compared to polypeptides? (8 points)

3. You are studying cells that normally respond to epidermal growth factor (EGF) by increasing their rate of cell division. You measure the cell division rate in the normal cells and the cells where a GTPase-activating protein (GAP) for Ras has been knocked down using small interfering RNA (siRNA). When the two types of cells are exposed to the same concentration of EGF, what differences in response to EGF do you expect? Explain your answer. (4%)

4.Acetylcholine-gated cation channels do not discriminate between Na+, K+, and Ca2+ ions, allowing all to pass through them freely. So why is it that when acetylcholine binds to this protein in the plasma membrane of muscle cells, the channel opens and there is a large net influx of primarily Na+ ions? (5%)

5.Ouabain is an African plant derivative that has been used historically to make poisontipped hunting arrows. it disables the main Na+/K+ ATPase in neurons. How would the resting potential of neurons in an organism exposed to ouabain change relative to the normal solution? (5%)

6.The drug Taxol, extracted from the bark of yew trees, has an opposite effect to the drug chochicine, an alkaloid form autumn crocus. Taxol binds tightly to microtubules and stabilizes them when added to cells, it causes much of the free tubulin to assemble into microtubules. In contrast, chochicine prevents microtubule formation. Taxol is just as harmful to dividing cells as chochicine, and both are used as anticancer drugs. Based on your knowledge of microtubule dynamics, suggest why both drugs are toxic to dividing cells despite their opposite action. (5%)

2. Which two amino acids are completely positively charged at physiological pH? (8 points)

3. Please describe or illustrate the structure (2 points) of ATP synthase and how this machinery links to the chemiosmotic hypothesis (6 points).

4. Please describe how starch is synthesized in plants (4 points) and how this process is regulated by photosynthesis (4 points).

5. How is the organic sulfide assimilated from sulfate? (8 points)

6. Please compare the carbamoyl-phosphate I and II according to their substrate; intracellular locations; involved pathways; regulators. (8 points)

7. How are eukaryotic transcripts processed and delivered to the ribosomes fortranslation? (8 points)