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Bio102 Problems Transport Across Membranes 1. Antiport is one type of A. facilitated transport. B. active transport. C. endocytosis. D. channel protein. E. carrier protein. 2. Pinocytosis is one type of A. exocytosis. B. phagocytosis. C. facilitated transport. D. endocytosis. E. diffusion. 3A. Consider a bacterial cell that is hypertonic in comparison to its environment. Will water move into the cell or out of the cell? in 3B. We now add a large amount of either O2, N2, or Pyruvate to the fluid surrounding the cell. Which one will have the biggest effect on the movement of water? Will its addition increase or decrease the movement of water? Please explain your answer. Pyruvate will have the biggest effect, decreasing the movement of water because the cell is less hypertonic (and may even be hypotonic). Oxygen and nitrogen both move through the membrane and thus don’t affect osmosis. 4. Imagine a bacterial cell living in a test tube under the following conditions: inside the cell outside the cell K+ Mg2+ Na+ 50 mM 10 mM 0.1 mM 3 mM 10 mM 150 mM 4A. Is the G value for Mg2+ movement into the cell positive, negative or zero? negative 4B. Under these conditions, is the solution hypotonic, hypertonic or isotonic relative to the cell? hypertonic 4C. Under these conditions, will the net movement of water be into the cell or out of the cell? Why? out of 4D. If we added a large concentration (say, 1M) of CO2 to the outside of the cell, it would have no effect on the net movement of water. Why not? CO2 can cross the membrane 4E. If the fatty acid tails in the phospholipids that make up this cell’s membranes were more saturated, would that increase or decrease the rate at which water moves? Or would it have no effect? Please explain. decrease. More saturations mean that it is less fluid and thus less permeable to everything, including water 5. Which one molecule might move across a membrane by simple diffusion? A. CO2 B. Glutamate (an amino acid) C. Insulin (a peptide hormone) D. K+ E. Maltose (a simple carbohydrate) 6. Which one statement does not accurately describe simple active transport? A. It requires a protein. B. Simple active transport is a type of endocytosis. C. Any type of substrate may be moved by simple active transport. D. ATP provides the energy for the movement. E. Simple active transport may be used to move a molecule against its concentration gradient. 7. A human liver cell is living in a a dish under the following conditions: Na+ SO42- Cl- K+ outside the cell 100 mM 0.1 mM 15 mM 15 mM inside the cell 10 mM 100 mM 15 mM 150 mM - + 0 + Gin value: 7A. For each ion, indicate in the table whether the G value for the movement of that ion into the cell is positive (+), negative (-) or zero (0). 7B. These cells use an antiporter protein to drive the uptake of SO42- into the cell. What other ion might be co-transported along with SO42-? Briefly describe how you arrived at your answer. Sodium would work. The movement of the second ion needs to release energy (G<0) to power the uptake of the sulfate. 7C. Under these conditions, is the cell hypotonic, hypertonic or isotonic relative to the solution? Hypertonic 7D. Under these conditions, will the net movement of water be into the cell or out of the cell? into 7E. If we added more cholesterol to this membrane, how would that affect the G values you described above? How would it affect whether the cell is hypertonic or hypotonic? How would it affect the rate at which the water moves? Or would it affect any of these? Please briefly explain your answer. It would have no effect on the G values above or the hyper/hypotonicity of the cell. Rather, it would affect the rate at which water (or anything else) moves by simple diffusion. 8. For each statement about membrane transport listed below, circle the type(s) of transport being described. Circle all that apply. Can be used to transport amino acids. Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport A sodium-magnesium symporter is an example of this type of transport. This type of transport always requires a protein. The transported molecule always follows its concentration gradient. Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport Uses energy in ATP to move a molecule. Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport Osmosis is one example of this type of transport. CO2 waste is removed from the cell by this type of transport Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport Simple Diffusion Facilitated Transport Simple Active Transport Coupled Active Transport 9. Match each statement to the type of transport being described. Notice that some statements may describe more than one type of transport; in those cases, list all that apply. Manganese ions could be moved by this type (or types) _FA____ of transport. The waste product of aerobic cell respiration is typically __P___ removed from the cell by this one type of transport. Some cells contain many copies of a Na+/Mn2+ __A____ antiporter. What type (or types) of transport is this? Increasing the number of unsaturations in the phospholipid tails would increase the rate of which one __P____ type of transport? A channel protein may be used for this type (or types) of __FA___ transport. P Passive Transport F Facilitated Diffusion A Active Transport N None of the above 10. It’s not surprising that meat spoils quickly if left at room temperature for just a few days, due to the growth of a large number of bacteria. However, if that meat is first treated with large amounts of salt (making beef jerky), it can be left at room temperature indefinitely without spoiling. Why? The high concentrations of salt draws nearly all of the water out of the meat cells by osmosis. With so little water left in the meat, it is impossible for it to spoil. 11. Which process is an example of endocytosis? A. Mitochondrial fission B. Antiport C. Oxidative phosphorylation D. Osmosis E. Pinocytosis 12. Imagine that we collect some white blood cells from a human donor and resuspend them in Phosphate-Buffered Saline (PBS). Under these conditions, the cells can live and be fully functional for several days. PBS consists of 10 mM sodium phosphate buffer at pH 7.4, 140 mM NaCl and 1M glucose and is isotonic to the cells. 12A. If we forgot to add any NaCl when preparing the PBS, what would happen to the white blood cells? Why? The PBS is no longer isotonic but is now hypotonic. Water will rush into the cells, leading to their lysis. 12B. If we accidentally added 280mM NaCl while preparing the PBS, what would happen to the white blood cells? Why? The PBS is no longer isotonic but is now hypertonic. Water will leave the cells, leading to their shrivelling. 12C. After they have lived in the test tube for several hours, we are able to detect increasing concentrations of lactic acid in solutions surrounding these cells. What can you conclude about the metabolic state of these cells? Do you also expect these cells to be producing CO2? Please briefly explain your answers. They are principally undergoing anaerobic metabolism. Very little CO2 will be produced, since the Kreb’s cycle is not extensively being used. 12D. What type of transport could be used by these cells to excrete the lactic acid? Please briefly explain your answer. Since this is a three-carbon acid, it can’t leave by simple diffusion. It must be leaving by facilitated or active transport. 13. For each statement about membrane transport listed below, circle the type (or types) of transport being described. Circle all that apply. Molecular oxygen enters a cell by this type(s) of transport. Antiport Endocytosis Exocytosis Facilitated Transport Osmosis Simple Active Transport Simple Diffusion Symport Cotransport includes this type(s) of transport. Antiport Endocytosis Exocytosis Facilitated Transport Osmosis Simple Active Transport Simple Diffusion Symport Antiport Endocytosis Exocytosis Facilitated Transport Osmosis Simple Active Transport Simple Diffusion Symport Antiport Endocytosis Exocytosis Facilitated Transport Osmosis Simple Active Transport Simple Diffusion Symport Antiport Endocytosis Exocytosis Facilitated Transport Osmosis Simple Active Transport Simple Diffusion Symport Proteins made on the Rough ER are secreted by this mechanism(s). A carrier protein can be used for this type(s) of transport. ATP is cut in this type(s) of transport.