1.Describe two variables that affect the rate of diffusion. a.Molecular weight b.Solute concentration 2.Why do you think the urea was not able to diffuse through the 20 MWCO membrane? How well did the results compare with your prediction? a.Urea was unable to diffuse through the 20MWCO membrane because urea is a big molecule and the 20MWCO membrane pore size was too small for Urea. My predication was accurate, as I predicted that Urea would not be able to diffuse through the 20MWCO membrane
3.Describe the results of the attempts to diffuse glucose and albumin through the 200 MWCO membrane. How well did the results compare with your prediction? a.Glucose was able to diffuse through the 200MWCO membrane at a 0.0040 rate. However, albumin was not able to diffuse through the membrane as predicted. Albumin is a large protein that was not able to diffuse through the pore size of a 200MWCO membrane. 4.Put the following in order from smallest to largest molecular weight: glucose, sodium chloride, albumin, and urea. a.Sodium Chloride, urea, glucose and albumin
Activity 2 Simulated Facilitated Diffusion
1.Explain one way in which facilitated diffusion is the same as simple diffusion and one way in which it differs. a.Both facilitated diffusion and simple diffusion move down a concentration gradient. b.Facilitated diffusion requires membrane carriers, while simple diffusion does not require it.
2.The larger value obtained when more glucose carriers were present corresponds to an increase in the rate of glucose transport. Explain why the rate increased. How well did the results compare with your prediction? a.When the glucose concentration increased, this increased the concentration difference between the two sides of the membrane. More molecules were available to pass through the membrane to reach equilibrium.
3.Explain your prediction for the effect Na+Cl− might have on glucose transport. In other words, explain why you picked the choice that you did. How well did the results compare with your prediction? a.I predicted that NaCl would not effect the glucose transport rate. I made this prediction because, NaCl was not required to transport glucose in the previous exercise and there was no indication that NaCl needed to use the same membrane carrier as glucose. So the NaCl would not interfere with glucose diffusion.
Activity 3 Simulating Osmotic Pressure
1.Explain the effect that increasing the Na+Cl− concentration had on osmotic pressure and why it has this effect. How well did the results compare with your prediction? a.When NaCl was increased on the left side, the water concentration on the left side decreased, thus, water wanted to move from the right to the left down its concentration gradient with more pressure. This lead to increase in pressure on the right side to prevent the water from crossing the membrane.
2.Describe one way in which osmosis is similar to simple diffusion and one way in which it is different. a.Both in simple diffusion and in osmosis, movement is from a higher concentration to a lower concentration. However in simple diffusion both water and solutes are able to diffuse, however in osmosis only water is able to diffuse.
3.Solutes are sometimes measured in milliosmoles. Explain the statement, “Water chases milliosmoles.” a.This statement refers to the fact that as the solute concentration increase, water concentration decreased. 4.The conditions were 9 mM albumin in the left beaker and 10 mM glucose in the right beaker with the 200 MWCO membrane in place. Explain the results. How well did the results compare with your prediction?
a.Because glucose is able to cross the membrane, equilibrium will be reached, with time both side had equal amounts of glucose. However, albumin is unable to cross the membrane, this will result in osmosis or an increase in osmotic pressure on the left to prevent water from crossing to the left side from the right. In this experiment, the osmotic pressure increased on the left side as I predicted it would.
Activity 4 Simulating Filtration
1.Explain in your own words why increasing the pore size increased the filtration rate. Use an analogy to support your statement. How well did the results compare with your prediction? a.I predicted that increasing the pore size would increase filtration rate and the results conformed with my prediction. By increasing the pore size more then one solute or solvent molecule can potentially pass through it, thus, increasing the rate of filtration. It is like having a one small hole on the piñata or one huge hole, the candy will fall faster from the bigger hole.
2.Which solute did not appear in the filtrate using any of the membranes? Explain why. a.Powdered Charoal did not appear in the filtrate using any of the membranes, because the membranes used did not have a pore size big enough to allow powdered charcoal molecules to pass through.
3.Why did increasing the pressure increase the filtration rate but not the concentration of solutes? How well did the results compare with your prediction? a.The increased pressure gave more force for the filtration to take place, which resulted in faster filtration rate, however the membrane can still prevent solutes from leaving with the filtrate to the same degree as it did with no pressure.
Activity 5 Simulating Active Transport
1.Describe the significance of using 9 mM sodium chloride inside the cell and 6 mM potassium chloride outside the cell, instead of other concentration ratios. a.The Sodium Potassium pump moves 3Na for every 2K the ratio is 3:2. 9mM sodium chloride and 6mM potassium chloride ratio is also 3:2. 2.Explain why there was no sodium transport even though ATP was present. How well did the results compare with your prediction? a.Because there was no potassium present, the sodium potassium carrier was not able to do any transfers as predicted.
3.Explain why the addition of glucose carriers had no effect on sodium or potassium transport. How well did the results compare with your prediction? a.The results agreed with my prediction that the addition of glucose carriers would not effect sodium or potassium transport. The reason why there was no effect was because glucose and sodium/potassium transport are independent of each other.
4.Do you think glucose is being actively transported or transported by facilitated diffusion in this experiment? Explain your answer. a.Glucose is not being actively transported because it is not using any energy (ATP). Glucose transport is through facilitated diffusion.