exam_2_review_problems

exam_2_review_problems - Exam 2 Review and Practice...

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Exam 2 Review and Practice Problems Chapter 10: Biomembrane Structure and Function Concept Review Questions 1. Biomembranes contain many different types of lipid molecules. What are the three main types of lipid molecules found in biomembreanes? How are the three types similar? How are they different? 2. Proteins may be bound to the exoplasmic or cytoplasmic face of the plasma membrane by way of covalently attached lipids. What are the three types of lipid anchors responsible for tethering proteins to the plasma membrane bilayer? Which type is used by cell- surface proteins that face the external environment? 3. Phospholipid biosynthesisat the interface between the endoplasmic reticulum and the cytosol presents a number of challenges that must be solved by the cell. Explain how each of the following is handled. a) The substrates for phospholipid biosynthesis are water soluble, but the end products are not. b) The immediate site of incorporation of al newly synthesized phospholipids is the cytoplasmic leaflet, yet phospholipids must be incorporated into both leaflets. c) Many membrane systems in the cell are unable to synthesize their own phospholipids, yet these membranes must expand if the cell is to grow and expand. 4. Explain the following statement: The structure of all biomembranes depends on the chemical properties of phospholipids, whereas the function of each specific biomembrane depends on the specific proteins associated with that membrane. 5. Name the three groups into which membrane-associated proteins may be classified. Explain the mechanism by which each group associates with a biomembrane. 6. Although both faces of a biomembrane are composed of the primarily of the same general types of macromolecules, the two faces are not identical. What accounts for the asymmetry between the two faces?
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Data Analysis Question: (This question should be challenging for you.) 1. Two membrane preparations have been derived from the plasma membrane of erythrocytes and are present in a buffer solution: (1) right-side-out membrane vesicles, in which the exoplasmic leaflet of the vesicle faces the buffer (equivalent in orientation to that of the exoplasmic leaflet of the intact plasma membrane); and (2) inside-out membrane vesicles in which the exoplasmic leaflet faces the interior of the vesicles. a. Annexin V is a protein that binds to phosphatidylserine, one of the phospholipids present in cell membranes. Fluorescently labeled annexin V is mixed with each vesicle preparation. The vesicles are washed to remove unbound annexin V and then examined by fluorescence microscopy. Presence of annexin V is detected by green fluorescence, as shown above. What can be deduced from these data? b.
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exam_2_review_problems - Exam 2 Review and Practice...

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