Download Midterm Exam 2 with Answer Key - Cell and Molecular Biology | BIO 310 and more Exams Cellular and Molecular Biology in PDF only on Docsity!
Bio 310 Midterm II, Winter ‘1 6 (Dr. Steve Alas)
NAME:_________________________________
(last) (first) INSTRUCTIONS
- This exam is 5 pages long, QUESTION VALUE including one extra credit page. Before starting, make sure you have all the pages. 1 10
- No credit will be given for an 2 10 illegible answer. Answers must be clear. I will not interpret vague responses. 3 10
- Partial credit will be given. 4 10
- You have enough space provided to answer 5 15 each question. Please be as brief as completeness allows. 6 15 7 15 8 15 Total 100 Extra Credit 9 8
KEY
Part I: Definitions
(10 points) 1. For each of the terms in the left column, choose the best matching phrase in the right column. Place the matching number in the space provided, left of the letter. 2 a. caveolin 1. secretion from a cell when a stimulus is given to the cell 10 b. uniport 2. protein that initiates plasma membrane invagination 19 c. adenylyl cyclase 3. Molecule used to produce different kinds of steroids 9 d. cytokine 4. The induction of arteries & arterioles to grow 8 e. transactivation domain 5. the carbohydrate-rich outermost face of the cell membrane 6 f. antiport 6. Coupled transport in opposite direction 12 g. SH2 domain 7. Used by cells to attach to one another 3 h. cholesterol 8. Region of protein responsible for transcription 15 i. polyubiquitination 9. Growth factor involved in cell stimulation through JAK/STAT 5 j glycocalyx 10. Individual transport of a molecule through a carrier 14 k. COPII 11. Stimulation of other cells in the environment 17 l. hemagglutinin 12. Region of a protein that binds to phosphorylated tyrosines 1 m. regulated pathway 13. Membrane region enriched in cholesterol & sphingolipids 13 n. lipid raft 14. Protein involved in stabilizing ER vesicles 7 o. glycolipid 15. The mechanism by which cells rid themselves of proteins 20 p. Ras 16. An example of a protein hormone 16 q. insulin 17. Protein used by influenza virus to enter cytoplasm 4 r. angiogenesis 18. Coupled transport in same direction 18 s. symport 19. Protein involved in generating cAMP from ATP 11 t. paracrine 20. Protein involved in activating the MAP kinase cascade
Part II: Basic Problems
( 10 pts) 2. Define and functionally distinguish between active and passive transport. Do not use the words “active” or “passive” as part of your actual definition and explanation. Both transport processes move things across the membrane. Active transport requires energy (ATP or light) and moves things against their concentration gradient. Passive transport does not require energy and moves things with their concentration gradient. ( 10 pts) 3. In order for glucose to be transported from the intestinal tract into the blood stream, the body uses glucose transporters. The glucose transporter uses Na+ to shuttle glucose. Why could the transporter not use K+ to drive glucose transport? Is the transport mechanism involving Na+ antiport or symport? Na+ concentration is greater outside the cell. Thus, the strong concentration gradient that induces Na+ to enter the cell is used to transport glucose into the cell in a SYMPORT fashion. The cell could not use K+ because it is more concentrated INSIDE the cell and has a tendency to exit the cell, following its concentration gradient. Therefore, K+ would never drive glucose INTO the cell.
Extracellular Cytoplasmic ( 15 pts) 7. You are examining the cellular response to a new drug. You treat cells with the drug and realize that it is binding and inhibiting COP I. How is the inhibition of COPI going to change what is happening in the cell? Or outside of the cell? Without COPI, vesicles will not be able to bud off of the golgi. Therefore, proteins will not get transported to the lysosome or to the surface of the cell. You, therefore, won’t be able to degrade any material that you bring in through endocytosis. You also won’t be able to put proteins on the outside surface of the cell, such as receptors. Additionally, the cell won’t be able to secrete anything to signal other cells. extracellular cytosol
(1 5 pts) 8. You are a new type of virus (no offense). You need to enter a host cell in order to replicate. Describe a way in which you could enter the cell and wind up in the cytoplasm. There are multiple ways. Design a mechanism of entry based on what we’ve learned. Students were free to use any mechanisms we saw in class. Students also got credit for being creative, unless the mechanism they invented surely did not make sense. Viruses can sit on the plasma membrane and wait to be endocytosed by invagination. Once in the endosome, a surface protein (ex. Hemaglutinin) could change shape as the pH dropped and take on a conformation that allowed it to imbed itself in the endosome membrane. This would cause the fusion of the endosome membrane and the virus, which would allow the virus to slip into the cytoplasm. Also, a virus can express receptors on its surface that grabs on to proteins on the cell membrane surface. This attachment can cause fusion of the viral envelope and the plasma membrane, allowing the virus to drop into the cytoplasm. The first example mimics influenza, while the second example mimics HIV.
Part IV: Extra Credit Problems
( 8 pts) 9. The plasma membrane is designed to block ions from entering the cell uncontrollably. If there is a large concentration of ion X+ outside the cell and low concentration of X+ inside the cell, how could the cell transfer X+ ions outside without letting any in? You can use any number of mechanisms, but you must explain their molecular mechanism. What kind of transport are you choosing? Would you power it or not? If so, how would you power it? Etc… There were different approaches students could take. To move against the gradient, you could design pumps that used energy to transport the ions toward the higher concentration. ATP could be used to power the pump. You could also use a carrier using coupled transport (symport, antiport) in which other ions powered the transport of X+. The carrier could also us ATP, which would provide a phosphate group that would change it’s shape in order to move X+ ions out of the cell, then use a phosphatase that would remove the phosphate group and return the carrier to its normal shape.
