Rate Of Diffusion Lab Report

Activity One:
1. The two major variables that affect the rate of diffusion:
a. The composition of the lipid bilayer (eg. more cholesterol, less permeability to polar substances)
b. The structure of the molecule undergoing diffusion (eg. steric conformation, size, polarity, amount and strength of hydrogen bonding)

2. Urea was not able to diffuse through the 20 MWCO because the pores of the membrane were too small for the urea to pass through. The molecular weight of urea is 60.06 g/mol, over three times greater than the 20 MWCO.

3. Glucose was able to diffuse through the 200 MWCO pore because it was small enough, having a molecular weight of 180.2 g/mol. Albumin was unable to pass through because it was far too large, having a molecular
weight in the range of 1000s of g/mol, far greater than the 200 MWCO.

4. For molecular weight: Sodium chloride < urea < glucose < albumin

Activity Two:
1.
Facilitated diffusion is similar to simple diffusion in the fact that it transports solutes from an area of high concentration to an area of low concentration; however it differs from simple diffusion because for the solute to pass, a protein transporter is required.

2. The increased number of glucose transporters allowed for an increased rate of glucose transport because more glucose molecules were able to bind to the transporters at the same time, thus allowing for an increased maximum rate of glucose transportation at saturation point.

3. When Na+ and Cl- ions were present in the solution, they had no effect on the transport of glucose because the transport of the ions and the transport of the glucose undergo diffusion using separate methods and thus are independent of each other.

Activity Three:
1. Increasing the Na+ and Cl- increases the osmotic pressure because raising the concentration of the solutes on one side of the membrane results in a larger concentration difference between both sides of the membrane. If the molecules were impermeable to the membrane, the only way to restore balance between concentrations would be for the movement of water across the membrane to the area of higher solute
concentration.

2.
Osmosis is similar to simple diffusion in that both processes are passive, allowing molecules to diffuse through a membrane from an area of high concentration to an area of low concentration without the input of energy; however it differs from simple diffusion in that during osmosis, water is the molecule being diffused, and is typically the solvent while in simple diffusion solute molecules are the molecules being diffused.

3. The statement, “water chases miliosmoles” means that as the solute concentration increases, the concentration of water decreases. When a difference of water concentrations occur between a membrane permeable to water, the water will diffuse to the area of lower water concentration (higher concentration of solute).

4. The glucose molecules were able to diffuse from the right beaker to the left beaker until equilibrium was reached, allowing both sides of the beaker to contain the same concentration of glucose. The albumin was not able to diffuse through the 200 MWCO membrane because it was too large thus resulting in osmotic pressure within the left side of the beaker.

Activity Four:
1. Increasing the pore size increases the filtration rate because more types of solutes can pass through the membrane. An analogy would be the size of the hole in an hour glass, the larger the hole, the more sand particles can flow through at the same time, thus increasing the rate of
transport.

2. Powdered charcoal was the only solute that did not appear in the filtrate using any of the membranes, due to the large size of the charcoal.

3. Increasing the pressure increased the filtration rate because the force causing the solutes to move was greater. The increased pressure did not increase the concentration of solutes that passed through the membrane because pressure is independent of the number of molecules present.
Activity Five:
1. The significance of using 9mM sodium chloride inside the cell and 6mM potassium chloride outside the cell is that 3 sodium ions are transported outside of the cell for every 2 potassium ions transported into the cell.

2. The reason sodium transport did not occur even in the presence of ATP is because in order for the Na+/K+ pumps to function, both ions must be present; excluding one of the two ions prevents the pump from working.

3. The presence of carriers had no effect on the sodium and potassium transport because the carriers are not used in the transport of sodium or potassium; they are used for molecules such as glucose.

4. Glucose is being passively transported down its concentration gradient by glucose transporters. This process is facilitated diffusion and does not require ATP.