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Cell Transport Mechanisms Essay

Describe two Variables that affect the rate of diffusion.

The two variables that affect the rate of diffusion are:

A. The size of the molecule. The larger molecule will diffuse more slowly than the smaller molecule. B. The nature of plasma membrane. If the membrane is composed of lipid portion., only lipid soluble molecules can pass through while water molecules cannot.

3. Why do you think the urea was not able to diffuse through 20 MWCO? How well did the results compare with your predictions?

The urea was not able to diffuse through 20 MWCO because the size of the pores of 20 MWCO was too small to allow the large size of molecules of urea to pass through. Since, the molecular weight of urea is 60.07, the molecules of urea were too large to enter the pores of the 20 MWCO.

4. Describe the result of the attempts to diffuse glucose glucose and albumin through the 200 MWCO membrane. How well did the results compared with your predictions?

Glucose could diffuse through the 200 MWCO while albumin could not diffuse through such membrane. It was because there was difference of molecule weight between them. Glucose (C6H12O6) has a molecular weight of 180 g/mol and albumin, which is protein with 607 amino acids, each single amino acid is 135 g/mole, has a molecular weight of(607 x 135) 81945 g/mole. Since the molecular of albumin is quite larger in molecular weight compared with glucose, it is absolutely believed that albumin was not able to diffuse the 200 MWCO.

I obtained the results from the experiment supported my predictions because only glucose could diffuse through the 200 MWCO while albumin could not.

5. Put the following in order from smallest to largest molecular weight: glucose, sodium chloride, albumin, and urea.

Sodium chloride < urea < glucose < albumin.

Activity 2: Simulated Facilitated Diffusion Lab Report

Review Sheet Results

1. Explain one way in which facilitated diffusion is the same as simple diffusion and one way in which it is different from simple diffusion.

One way in which facilitated diffusion is the same as simple diffusion is that they both transport solutes with(or along or down) their concentration gradient and they do not required the energy of ATP to support the transport.

One way in which facilitated diffusion is different from simple diffusion is that facilitated diffusion requires the help of carrier proteins bound in the membrane to transport molecules across the membrane. On the other hand, simple diffusion does not require the help of membrane proteins.

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 result compare with your predictions?

When more glucose carriers were present, the rate of glucose transport increased. It was because with the increase in glucose carriers, more glucose molecules could bind to the carriers and that would result in an increase number of glucose molecules get across the membrane.

I obtained the results from the experiment supported my predictions because when there was an increase in number of glucose carriers, the rate of glucose transport would also increase with the help of facilitated diffusion.

3. Explain your prediction of the effect of Na+ Cl- might have on glucose transport. In other words, explain why you picked the choice you did. How well did the results compare with your prediction?

Na+ Cl- will have no effect on the rate on glucose transport since Na+ Cl- is transported through a simple diffusion without the help of a carrier protein. Adding Na+ Cl- will not affect the rate of glucose transport because the Na+ Cl- transport is completely independent from the glucose transport.

I obtained the results from the experiment supported my predictions because from run number 6, the effect of Na+ Cl- did not affect the rate of glucose transport.

Activity 3: Simulating Osmotic Pressure Lab Report

1. Explain the effect that increasing the Na+ Cl- concentration has on osmotic pressure and why it has this effect. How well did the results compare with your prediction?

Increasing the Na+ Cl- concentration in the left beaker while keeping the size of MWCO at 20 would result in an increase in osmotic pressure (Run No.2). This was because the high concentration of Na+ Cl- in the right side of membrane gives a increased force to water (in left beaker) to move towards the solution with the highest concentration of solutes. Therefore, there was an increase in osmotic pressure.

However, when the membrane was changed to from 20 MWCO to 50 MWCO, the Na+ Cl- molecules were able to diffuse through the membrane, the equilibrium would be reached and no osmotic pressure was generated. If the concentration of Na+ Cl- of both size are equal, the osmotic pressure would be zero.

I obtained the results from the experiment supported my predictions because as the the concentration Na+ Cl- was increased from 5 mM to 10 mM (by adding more Na+ Cl-), the osmotic pressure also increased. However, after the membrane was changed to 50 MWCO, the Na+ Cl- molecules could diffuse easily through the membrane and did not caused an increase in osmotic pressure.

2. Describe on way in which osmosis is similar to simple diffusion and on way in which is different.

One way in which osmosis is similar to simple diffusion is that both mechanisms are passive that involve movement of a substance from an area of its high concentration to an area of its lower concentration, that is, with (or along or down) its concentration gradient without the input of energy.

On way in which osmosis is different from simple diffusion is that ions and molecules are transported through the membrane while in osmosis water molecules are transported through a selectively permeable membrane.

3. Solutes are sometimes measured in millisomoles. Explain the statement, “Water chases millionsoles.”

It means when the concentration of solutes increase, the concentration of water decrease. Osmosis is the process of diffusion of water. It happens when there is difference of water concentration between two places which is separated by a membrane. Water will diffuse from a low concentration of solutes from one size to a higher concentration of solutes of the other size.

4. The conditions of 9mM albumin in the left beaker and 10mM glucose in the right beaker with 200 MWCO membrane in place. Explain the results. How did the results compared with your prediction.

The molecules of 10mM glucose could pass through the 200 MWCO membrane from the right beaker to left beaker until the equilibrium was reached. At this point, the concentration of glucose between two sides is equal. On the other hand, the molecules of 9 Mm albumin could not pass through the 200 MWCO membrane that kept in the left beaker and a osmotic pressure of 15m mmHg was built up.

I obtained the results from the experiment supported my predictions because glucose could diffuse through the 200 MWCO while albumin could not do so. Thus, a osmotic pressure was built up in the left size of beaker.

Activity 5: Stimulating Active Transport

1. Describe the significance of using 9 mM sodium chloride inside the cell and 6mM potassium chloride outside the cell instead of other concentration ratios.

The significance of using 9 mM sodium chloride inside the cell and 6 mM potassium chloride outside the cell is that for every three a+ ions transported out of the cell, two K+ ions are transported into the cell. The ratios of ions being out and in is 2: 3 is the same as the concentration ratio of 6 mM : 9 mM.

2. Explain why there was no sodium transport even though ATP was present. How well did the results compare with your prediction?

The reason there was no sodium transport even though ATP was present because in order to make Na+/Ka+ pump perform successful, both Na+ ions and Ka+ ions must be present. . In Stimulation Run Number 3, there was no Ka+ present, therefore the pump could not function.

I obtained the results from the experiment supported my predictions because no sodium transport could be observed even with the presence of ATP.

3. Explain why the addition of glucose carriers had no effect on sodium or potassium transport. How well did the results compared with your prediction?

The addition of glucose carriers had no effect on sodium or potassium transport because the carriers were used to transport the glucose molecules by facilitated diffusion without the input of ATP.

On the other hand, Na+ and Ka+ ions are transported actively by Na+/Ka+ pump across their concentration gradient, if glucose carriers were added, they had no effects on the transport of Na+and Ka+ ions

I obtained the results from the experiment supported my predictions because the addition of carriers had no effect on the Na+and Ka+ ion transport.

4. Do you think glucose is being actively transported or transported by facilitated diffusion in this experiment? Explain your answer.

From Run Number 5, Glucose molecules were transported passively by facilitated diffusion down their concentration gradient without the input of ATP. The presence of carriers were used to help the glucose molecules to get across the membrane.


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