Title: Physioex 8.0 Answers to simple diffusion Post by: michelle.mckain.love on Sep 6, 2011 Answers to Questions
Activity 1: Simulating Dialysis (Simple Diffusion) (pp. 2–4) 9. All solutes except albumin are able to diffuse into the right beaker. Using distilled water in the right beaker and either the 100 MWCO or 200 MWCO membrane will remove urea from the left beaker and leave albumin If the left beaker contains NaCl, urea, and albumin, you can selectively remove urea by dispensing a concentration of NaCl into the right beaker equivalent to that in the left beaker and by using the 100 or 200 MWCO membrane. Albumin is too large to diffuse and there will be no net diffusion of NaCl. However, urea will move down its concentration gradient into the right beaker. Activity 2: Simulating Facilitated Diffusion (pp. 4–5) 11. Carrier proteins facilitate the movement of solute molecules across semipermeable membranes, so increasing their number will increase the rate of diffusion. Because facilitated diffusion requires a concentration gradient, making the concentration on both sides of the membrane equal stops net diffusion. NaCl does not have an effect on glucose diffusion. Activity 3: Simulating Osmotic Pressure (pp. 6–7) 6. Using the 20 MWCO membrane results in an osmotic pressure increase using any of the solutes. The 50 and 100 MWCO membranes caused osmotic pressure increase with albumin and glucose. Only albumin caused osmotic pressure increase using the 200 MWCO membrane. NaCl appeared in the right beaker with all membranes except the 20 MWCO membrane. 8. Increasing the number of non?diffusible particles increases osmotic pressure. If solutes are able to diffuse, then equilibrium will be established and osmotic pressure will not be generated. Osmotic pressure would be zero if albumin concentration was the same on both sides of the membrane. If you increased (or doubled) the concentration of albumin, osmotic pressure will increase (or double). Glucose is freely diffusible using the 200 MWCO membrane and therefore has no effect on osmotic pressure. The 100 MWCO membrane does not allow glucose to pass and therefore glucose will generate an osmotic influence. Because albumin concentration in the left beaker is 9.00 mM and glucose concentration in the right beaker is 10.00 mM (1.00 mM higher than the left), the small gradient dictates that an osmotic pressure increase will appear in the right beaker. Activity 4: Simulating Filtration (pp. 7–9) 9. Smaller MWCO numbers translate to smaller pore sizes, which correlate with lower filtration rate. Powdered charcoal did not appear in the filtrate using any membrane. Increasing the force driving filtration increases filtration rate. Increasing the pressure gradient effectively increases the filtration rate. By examining the filtration results, we can predict that the molecular weight of glucose must be greater than NaCl but less than powdered charcoal. Activity 5: Simulating Active Transport (pp. 10–11) 7. Solute transport stops before the completion of transport because of a lack of ATP. Sodium and potassium transport will not occur if ATP is not available. 8. Yes, transport has changed because more ATP is available. This fact supports the earlier supposition that ATP is required for active transport. The rate of active transport will decrease if fewer solute pumps are available, but will still go to completion given enough ATP and time. You can show that this is an active process by making the sodium concentration in the right beaker greater than the sodium concentration in the left beaker. Transport will occur against the concentration gradient in active transport but not in diffusion. 9. Sodium transport is not affected by putting NaCl into the right beaker. Increasing the number of pump proteins will increase solute transport. Glucose presence does not affect active transport. Simple Diffusion None Albumin NaCl The smaller the solute particle the greater the rate of diffusion. Facilitated Diffusion No; in facilitated diffusion, a passive process, substances can move only down their concentration gradient. 0.0038 8mM glucose with 900 glucose carriers in the membrane Increase amount of glucose in solution; increase number of glucose carriers in the membrane No No; because of its small size, NaCl is able to diffuse down its concentration gradient without the aid of carriers. Osmotic Pressure 20 MWCO Buildup of osmotic pressure due to the presence of non?diffusable NaCl in the solution causes water to diffuse down its concentration gradient. 200 MWCO There was no buildup of osmotic pressure, which indicates that glucose is able to diffuse down its concentration gradient. No The higher the solute concentration, the higher the osmotic pressure. Filtration 200 MWCO The larger the pore size, the greater the filtration rate. Powdered charcoal The filtration rate of glucose is less than that of NaCl and urea, so its molecular weight would be greater. The filtration rate increases. Pressure is higher in capillaries than in kidney tubules so particles that are small enough are filtered from capillaries into kidney tubules. The rate of filtration would decrease. No; ATP was depleted at 3 minutes. The rate of active transport decreases. Sodium moved from the left beaker into the right beaker against its concentration gradient; there was no movement of sodium when there were no Na!/K! pumps added to the membrane. Title: Re: Physioex 8.0 Answers to simple diffusion Post by: Ame on Sep 6, 2011 SWEATNESS
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