Cell Transport Mechanisms and Permeability Persuasive

1. What is the molecular weight of Na+?

The molecular weight of Na+ is 23.

2. What is the molecular weight of Cl-?

The molecular weight of Cl- is 35.

3. Which MWCO dialysis membranes allowed both of these ions through?

The MWCOs that allowed both of these ions through were 50,100 MWCO and 200 MWCO.

13. Which materials diffused from the left beaker to the right beaker?

NaCl, Urea, and Glucose were the materials that diffused from the left to the right beaker.

Which did not?

Albumin did not diffuse from the left to the right.

Why?

Albumin is a protein, which means it is a thicker substance, and the molecular weight was greater than the MWCO.

Activity 3
Facilitated Diffusion

12. At a given glucose concentration, how does the amount of time it takes to research equilibrium change with the number of carriers used to “build” membrane?

At a given glucose concentration, the time decreases as the carriers get more to “build” membrane.

Does the diffusion rate of Na+/Cl- changes with the number of receptors?

No the diffusion rate of Na+/Cl- does not change with the number of recpetors.

What is the mechanism of the Na+/Cl- transport?

Simple diffusion is the mechanism of the Na+/Cl- transport.

If you put the same amount of glucose in the right beaker as in the left, would you be able to observe any diffusion?

Yes, if you put the same amount of glucose in the right beaker as in the left, you would be able to observe diffusion.
Does being unable to observe diffusion necessarily mean that…….?
Yes, diffusion is taking place.

Review Questions

1. Match each of the definitions in Column A with the appropriate term in Column B. Column A
_e. Hypotonic__ term used to describe a solution that has a lower concentration of solutes compared to another solution. _g. Hypertonic__ term used to describe a solution that has a higher concentration of solutes compared to another solution. _a. Diffusion___the movement of molecules from an area of higher concentration to an area of lower concentration as a result of random thermal motion. _d. active transport___ the movement of molecules across a membrance that requires the expenditure of cellular energy (ATP) _c. Osmosis___ the transport of water across a semipermeable membrane. _f. Isotonic__ term used to describe two solutions tha have the same concentration of solutes relative to one another. _b. Facilitated diffusion___ the movement of molecules across a selectively permeable membrane with the aid of specialized transport proteins.

Column B
a. Diffusion
b. Facilitated diffusion
c. Osmosis
d. Active transport
e. Hypotonic
f. Isotonic
g. Hypertonic

2. What is the main difference between simple diffusion and facilitated diffusion?

The main difference between simple diffusion and facilitated diffusion is that in facilitated diffusion a carrier protein is used.

3. What is the main difference between facilitated diffusion and active transport?

The main difference between facilitated diffusion and active transport is that in active transport the solutes are moved from an area of low concentration to an area of high concentration, which is the opposite of facilitated diffusion. Also in facilitated diffusion binding to a transporter is needed.

4. In the “Simple Diffusion” experiment, which solute(s) passed through the MWCO 20 membrane? Why?

None of the solutes passed through the MWCO 20 membrane because the solutes molecular weights were greater than the MWCO 20 membrane.

5. List three examples of passive transport mechanisms.  Three examples of passive transport are osmosis, simple diffusion, and facilitated diffusion.

6. Describe the relationship of solute concentration to solvent concentration in osmosis.

The concentration of the solute is higher than the concentration of the solvent when describing the relationship in osmosis.

8. How can the concentration of water in a solution be decreased?

Increasing the solute will decrease the water concentration because the solution concentration is the inverse of the solvent concentration.

9. Suppose that a membrane separates a solution of higher osmolarity and a solution of lower osmolarity. To prevent osmotic flow of water across the membrane, pressure should be applied to which of the two solutions?

It should be applied to the higher osmolarity. The solution with the higher osmolarity has a higher concentration of solute and low concentration of water, which means this specific solution would need to have pressure present to block waterfront coming in from the solution of lower osmolarity.

10. What change in the cell volume will occur when a cell is placed in a hypotonic solution?

In a hypotonic solution the cell will expand. The water will move from the solution into the cell and if enough water moves into the cell it will explode.

11. What change in the cell volume will occur when a cell is placed in a hypertonic solution?

When a cell is placed in a hypertonic solution water will move out of the cell, causing the cell to shrink and die.

12. By what mechanism does the active transport of sodium lead to osmotic flow of water across a membrane?