2. (6 points) You have prepared lipid vesicles (spherical lipid bilayers) that contain Na+-K+ pumps as the sole membrane protein. Assume for the sake of simplicity that each pump transports one Na+ one way and one K+ the other way in each pumping cycle, as illustrated below. All of the Na+-K+ pumps are oriented so that the portion of the molecule that normally faces the cytosol faces the outside of the vesicle. Predict what would happen under the following conditions (1 point, each prediction). Explain your reasoning (1 point, each explanation, 1-2 sentences) a. (2 points) The solution inside the vesicles contains both the Na+ and K+ ions; the solution outside also contains both ions, as well as ATP b. (2 points) The solution inside and outside the vesicles contains both Na+ and K+ ions, but no ATP. c. (2 points) The solution is as in A, but the Na+-K+ pump molecules are randomly oriented, some facing one directions, some the other
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- The vesicles contain Na+ and K+ ions inside. - The outside solution contains Na+, K+, and ATP. - The Na+-K+ pumps are oriented with the cytosolic side facing outside. Show more…
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You have constructed phospholipid vesicles that contain Na+/K+ pumps as the sole membrane protein. The portion of the pump that normally faces the cytosol is oriented towards the outside of the vesicles. The solutions inside the vesicles and outside the vesicles have both Na+ ions and K+ ions, but ATP is not present on either side. What would happen? Select an answer and submit. a Very little Na+ would move inside the vesicle (only one partial cycle of all the pumps would occur, moving a single cycle of Na+ to the inside of the vesicle) b Very little Na+ would move outside the vesicle (only one partial cycle of all the pumps would occur, moving a single cycle of Na+ to the outside of the vesicle). c Na+ and K+ would be pumped repeatedly out of the vesicle. d Na+ and K+ would be pumped repeatedly into the vesicle. e No Na+ or K+ would move.
Sri K.
Lipid vesicles (small spherical bilayers) provide an ideal in vitro system for the study of pumps and channels. You have prepared lipid vesicles that contain Na+/K+ pumps. The pumps are oriented such that the portion of the pump that normally faces the cytoplasm is facing the outside of the vesicle. Predict what would happen under each of the following conditions (for simplicity, assume that the ions are pumped in a 1:1 ratio). a. The solution on the inside and outside of the vesicles contains both ions, but no ATP. b. The solution inside the vesicle contains both ions; the solution outside contains both ions and ATP. c. The solution inside contains sodium ions; the solution outside contains sodium ions plus ATP. d. The solution as in part B, but the pumps are randomly oriented, some facing outward and some facing inward.
The sodium-potassium (Na^ + $/ \mathrm{K}^{+}$ ) pump functions like an anti-porter transporting $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ across membranes using ATP. This protein spans the membrane with intracellular and extracellular domains. It has a binding site for $\mathrm{Na}^{+}, \mathrm{K}^{+},$ and ATP. An experiment was conducted to determine the locations of these binding sites. Artificial cells were created and incubated in buffers containing ATP, ouabain (or oubain), $\mathrm{Na}^{+},$ and $\mathrm{K}^{+}$ in varying combinations inside and outside of the cell as indicated in the chart. The transport of $\mathrm{Na}^{+}$ and $\mathrm{K}^{+}$ was measured to determine activity of the $\mathrm{Na}^{+} / \mathrm{K}^{+}$ pump. Which of the following conclusions is supported by the data? a. Ouabain can disrupt ATp binding to the $\mathrm{Na}^{+} / \mathrm{K}^{+}$ pump. b. ATp is required for transport of $\mathrm{Na}^{+}$ and not for transport of $\mathrm{K}^{+}$ . c. The ATP binding site of the $\mathrm{Na}^{+} / \mathrm{K}^{+}$ pump is located on the intracellular domain of the pump. d. The ATP binding site of the $\mathrm{Na}^{+} / \mathrm{K}^{+}$ pump is located on the extracellular domain of the pump.
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