Assignment Example on Cell Transport Mechanisms and Permeability

ACTIVITY 1: Cell Transport Mechanisms & Permeability: Simulating Diffusion (Simulating Dialysis)

1. Two variables influence the rate of diffusion.

The rate of diffusion is affected by molecular weight. A larger molecule will diffuse faster if it has a greater mass. The rate of diffusion is also affected by membrane size. If the pores on the membrane are smaller, it will take molecules more time to diffuse through it than if they were larger. The membrane thickness also plays a role in the speed of diffusion.

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2. What is the reason why the urea could not diffuse through the 20MWCO membrane? What did the actual results show?

Our prediction was that urea would not be able diffuse through the 20 Molecular Weight Cut Off membrane (MWCO). This is because urea is too large a molecule for it to diffuse through 20 MWCO membrane's pores.

Our prediction was right, the Urea could not diffuse through such a small membrane.

3. Describe the results from the experiments to diffuse glucose through the 200MWCO membrane. What did the results show? How does it compare to your prediction?

Because they are large molecules, we predicted that albumin and glucose would diffuse slowly through the 200 MWCO. The glucose was able to diffuse through the 200 MWCO membrane at a rate 0.0040 per hour. Because the albumin molecules are too large to pass through the membrane pore, it was unable to diffuse through 200 MWCO.

4. The following are listed in alphabetical order, from smallest to most molecular weight: glucose (no sodium chloride), albumin, and the urea.

Sodium Chloride and Urea, Glucose and Albumin.

ACTIVITY 2: Cell Transport Mechanisms and Permeability - Simulated Facilitated Difusion

1. Explain how facilitated diffusion differs from simple diffusion.

Facilitated diffusion works in the same way as simple diffusion, except that they both go down (or with the concentration gradient) and are passive. Facilitated diffusion is different than simple diffusion because it uses a carrier protein for transporting the material across the membrane.

2. A higher rate of glucose transport is indicated by a larger value when there were more glucose carriers. Explain the reason why the rate increased. What did the prediction hold up?

Because glucose concentration increased, the rate at which glucose was transported increased. The rate of diffusion increases with a higher concentration gradient. Consequently, the glucose diffuses faster through the membrane if there are more glucose carriers. Although we predicted slower diffusion due to more molecules, the actual result was opposite. We didn't know anything about Fick's Law of diffusion at the time.

3. Describe your prediction about the effects Na+ Cl- could have on glucose transport. Also, tell us why you made the decision you did. What did the prediction hold up?

We expected that the glucose transport rate would rise. This was because we believed that Na+Cl would allow the glucose molecules to diffuse through the membrane faster than without it. Our prediction was confirmed by our results. The Na+Cl+ helped glucose through the membrane faster.

ACTIVITY 3: Cell Transport Mechanisms and Permeability - Simulating Osmotic Pressure

1. Explain the impact that increasing the Na+ Cl+ concentration has on osmotic tension and the reasons for this effect. What did the results show? How does it compare to your prediction?

We increased the Na+Cl- concentration, which changed the concentration gradient of the water. This raised the osmotic tension. We predicted that adding more Na+Cl would increase the osmotic Pressure and speed up diffusion. Our results were in line with our predictions.

2. Discuss one way that osmosis can be similar to simple diffusion, and one way it can be different.

Simple diffusion is similar to Osmosis in that it is passive diffusion and moves down concentration gradient. Osmosis is a process that occurs when there is a gradient in concentration across a membrane.

3. Sometimes, solutes can be measured in milliosmoles. Explain the statement "Water chases milliosmoles."

Water chases milliosmoles refers to water diffusion or osmosis. Water can move through most membranes quickly and when there is an increase in water concentration between the membrane sides, it moves. This is called water chasing the concentration gradient.

4. The conditions were 9mM albumin and 10mM glucose in the left beaker, with the 200MWCO membrane in place. Describe the results. What did the results show?

The results showed that albumin could not pass through the membrane due to its too large molecule. However, glucose passed through the membrane at a rate 0.0044 per hour. Both were at 153 L osmoticpressure. However, albumin could not pass through the membrane due to its large size. Both would have diffused through the membrane if they were at a higher osmotic level, but glucose was the only molecule that could diffuse through it.

ACTIVITY 4: Cell Transport Mechanisms and Permeability - Simulating Filtration

1. Explain why increasing the size of the pores increased the filtration rate. To support your argument, use an analogy. What did the results say about your prediction?

The filtration rate rose by increasing the size of the pores in the membrane. This is because more molecules could diffuse through the larger pores faster than the smaller ones. We predicted that the rate would rise because larger pores allowed more molecules to pass through them. The membrane pores in the kidneys are larger, which allows glucose and other urea to pass through the pores.

2. Which solute was not found in the filtrate without any membrane? Please explain why.

The membranes did not contain powdered charcoal because the molecules were too large to pass through the membrane pores.

3. What is the difference between increasing pressure and increasing solute concentration? What did the actual results show?

Increased pressure caused the filtration to take place faster but it did not affect the concentration of the solutes. Pressure is what determines how fast the filtrate diffuses and not how much.

It passes through the membrane. We expected that the rate would rise.

ACTIVITY 5: Cell Transport Mechanisms and Permeability - Simulating Active Transportation

1. Explain the importance of using 9 mM sodium chlorineide inside and 6 mM potassium saltide outside cells, in place of other concentrations.

These concentrations are more important than any other ratios because for every 3 Na+ions that leave a cell, 2 K+ions enter it. We were also able to determine the rate at which diffusion occurs.

2. Explain why sodium transport was not possible despite the presence of ATP. What did the prediction hold up?

Because there is more Na+ in the cell than inside, Na+ tends not to move out of the cell.

3. Explain why adding glucose carriers to sodium and potassium transport had no effect. What did the result compare to your prediction?

Because glucose is transport independently, it has no effect on Na+ and K+.

4. Is glucose being transported actively or by facilitated diffusion? Please explain your answer.

Glucose has been actively transported by this experiment, because it was transported with the ATP.