Cell Transport Mechanisms and Permeability

Cell Transport Mechanisms and Permeability

REVIEW SHEET EXERCISE 1 Cell Transport Mechanisms and Permeability NAME: LAB TIME/DATE: 1. Match each of the definitions in Column A with the appropriate term in Column B.

Column AColumn B __E__ term used to describe a solution that has a lower concentration of solutes compared to another solution _G___ term used to describe a solution that has a higher concentration of solutes compared to another solution _A___ the movement of molecules from an area of higher concentration to an area of lower concentration as a result of random thermal motion _D___ the movement of molecules across a membrane that requires the expenditure of cellular energy (ATP) _C___ the transport of water across a semipermeable membrane _F___ term used to describe two solutions that have the same concentration of solutes relative to one another __B__ the movement of molecules across a selectively permeable membrane with the aid of specialized transport proteinsa. 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?

Simple diffusion moves molecules from an area of higher concentration to an area of lower concentration without an input of energy. Facilitated Diffusion follows the same rules as regular diffusion (higher to lower concentration and no energy input), but uses protein carrier molecules to allow substances that are fat soluble to diffuse through the cell membrane. 3. What is the main difference between facilitated diffusion and active transport? Facilitated Diffusion molecules move from a high concentration to a low concentration without the requirement of ATP. The movement of molecules AGAINST the concentration gradient with the use of energy (eg, ATP) 4. In the “Simple Diffusion” experiment, which solute(s) passed through the MWCO 20 membrane?

None of the substances passed through the MWCO 20 membrane. The molecular weight cut off (MWCO) was to high- molecules with a higher molecular weight values cannot pass through the membrane. 5. List three examples of passive transport mechanisms. Diffusion, Facilitated Diffusion, and Osmosis. 6. Describe the relationship of solute concentration to solvent concentration in osmosis. The relationship is this: when the solute concentration is higher, water potential is lower, and Vice Versa. 7. What is the equation for Fick’s First Law of Diffusion? Jnet=dQs/dt=-DA(dc/dx) 8. In the mock dialysis activity, what was the only solute removed from the beaker representing the patient’s blood? Glucose.

Why is it important that this solute be removed from diabetic patients? The main job of insulin is to keep the level of sugar in the bloodstream within a normal range. After you eat, carbohydrates break down into sugar and enter the bloodstream in the form of glucose, a sugar that serves as a primary source of energy. Normally the pancreas responds by producing insulin, which allows sugar to enter the tissues. If too much insulin is produced it could be deadly as well as vise versa. 9. How can the concentration of water in a solution be decreased? You could also use dialysis to decrease the water concentration, placing your solution inside a dialysis bag.

Then, you would place the bag in a solution that has a high concentration of an ion (NaCl). Water will attempt to balance the concentration gradient by rushing out of the bag. As long as there is nothing critical in the solution smaller in size than water, this technique should work. Distillation may allow you to control more exactly how much water you are losing, as you might not be certain of the appropriate concentration of ions for your dipping solution. 10. 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? 11.

What change in cell volume will occur when a cell is placed in a hypotonic solution? The cell will expand in a hypotonic solution. 12. What change in cell volume will occur when a cell is placed in a hypertonic solution? The cell will shrink in a hypertonic solution. 13. By what mechanism does the active transport of sodium lead to osmotic flow of water across a membrane? By an active transporter protein on the cell membrane (usually a sodium-potassium pump) expends ATP to either pump Na+ into or out of the cell. If it pumps Na+ out of the cell, the salt concentration of the cell decreases, thus decreasing its osmotic pressure and water exits passively through the cell.

If the membrane protein pumps Na+ into the cell, the salt concentration increases as does the osmotic pressure causing water to passively enter the cell. 14. If two solutions having different osmolarities are separated by a water-permeable membrane, will there be a change in the volume of the two compartments if the membrane is impermeable to solutes? Will there be a change in the volume of the two compartments if the membrane is permeable to solutes? No there will be a change in in volume of the two compartments. Yes there will be a change in volume of the two compartments. Any change of volume will be due to movement of solvent e. g. water, while the solute is prevented from moving. Other result: the osmotic concentrations will become more balanced.


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