Zephyr Case Study

1. In class, we discussed some experiments that demonstrated the importance of a homotypic cell adhesion molecule receptor for cell-cell adhesion. These experiments used L cells and calcium ions. The conclusions from these experiments were: i) Integrins are the key homotypic cell-cell adhesion receptor ii) Calcium is needed for the receptor to function in cell-cell adhesion iii) L cells are non-adherent cells unless they have a cell adhesion receptor iv) L cells with different amounts of the same cell adhesion receptors can sort themselves out and become layered 2. Proteoglycans promote hydration of surrounding cells, primarily due to: i) the presence of large amounts of N-linked complex oligosaccharides ii) high levels of the mannose-6-phosphate modification iii) The strong negative charge of GAGs. iv) the presence of many Gly-X-Y repeats v) All of these vi) None of these 3. Which of the following proteins assemble into polymers on the outside of the cell? i) tubulin ii) collagen iii) fibronectin iv) dolichol v) mRNA vi) none of these 4. Briefly explain why each of the following mutations or drug treatments would prevent the formation of fibronectin fibrils. i) Integrin beta subunit mutation in cytosolic tail

ii) Mutation of the RGD motif in fibronectin

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5. (10 pts) The intestinal epithelium is faced with the complex task of providing a barrier while also allowing nutrient and water absorption. i) On Cell #1 on the diagram below, draw an arrow to AND name the structure that is responsible for both the barrier function (distinct ionic compositions on either side of the epithelial sheet) and the nutrient absorption.

ii) To explain how this structure allows for nutrient absorption from the gut lumen to the blood to occur, do the following two things. a) On Cell #2, draw the localization of the transporters that mediate glucose absorption (use circles for apical and...