Question

HdDUCIRUDUCULUD HUDUCU HUDDLDI AUDULLDI HUDDLED Heading 1 Heading 2 Title Subtitle Subtle Em... Emphasis intense E... Styles 4. You now are given a normal sample of muscle tissue which contains many individual cells. The tissue is minced and digested with enzymes to liberate individual muscle cells. You are given a solution of Dextrose in half-normal saline (NaCl) which you are told is isosmotic but you are not told the concentration of Dextrose or NaCl but they are both present in the solution. In this case Dextrose is permeable to the cell. You place the isolated muscle cells in this solution. Assume all of the solutes inside the cell are not permeable to the cell membrane. What happens to the cells when you place them in this solution and it has reached equilibrium? (4 Points) a. The cells remain the same size b. The cells have increased in size, they swell c. The cells have decreased in size; they shrink d. There is not enough information given in the problem to determine what happens Assume that Solution A by itself is hyposmotis to cells in each of the following questions (5-8) and that you don't know the concentration of non-penetrating and penetrating solutes in Solution A. All of the solutes in the cell are non penetrating. Circle the correct response for each part below. (4 points) 5. Solution A is hyposmotic to cells. What can you say about the tonicity solution A? a. Solution A is hypotonic b. Solution A is isotonic c. Solution A is hypertonic d. Solution A could be hypotonic, isotonic or hypertonic e. Solution A could be hypotonic or isotonic, but not hypertonic 6. Solution A +5% Glucose (a penetrating solute) is hyperosmotic to cells. What can you say about the tonicity of this mixture? (4 points) a. Solution A + 5% Glucose is hypotonic b. Solution A + 5% Glucose is isotonic c. Solution A +5% Glucose is hypertonic d. Solution A + 5% Glucose could be hypotonic, isotonic or hypertonic e. Solution A+ 5% Glucose could be hypotonic or isotonic, but not hypertonic

Answer 1

1. The solution’s tonicity depends on the solution’s concentration of nonpenetrating solutes (e.g., NaCl) relative to that in the cell, not on the total osmolarity of the solution.
2. Tonicity provides the information on how the solution affects the cell’s volume once osmotic equilibrium is reached; that is, when the osmolarities of the solution and the cytosol become equal.
3. Water molecules move faster through the cell membrane than particles of solute do. Therefore, a cell placed in a hyperosmotic solution will always shrink initially, regardless of the solution’s tonicity
Osmolarity is an important property of any biological solution. But just as knowing the molarity of a solution does not tell us its osmolarity, knowing the osmolarity of a solution does not tell us its tonicity. This is because tonicity is a term that requires two compartments: the solution being described and a cell. In addition to knowing the concentration (osmolarity) of the solution, you must know the composition of the solution: what the solutes are and whether or not they can enter the cell. Solutes that enter a cell by any means (simple diffusion, protein-mediated transport, and so on) are said to be “penetrating” solutes. Solutes that do not enter the cell are said to be “nonpenetrating” solutes.
The tonicity of a solution predicts the effect of the solution on cell volume at equilibrium and depends on the relative concentrations of nonpenetrating solutes in the cell and the solution. At equilibrium, water movement into the compartment with the higher starting concentration of nonpenetrating solutes will increase that compartment’s volume. Net water movement stops when the concentrations of nonpenetrating solutes in the cell and solution are equal. The cell’s volume change in response to the solution tells us the tonicity of the solution:
• If cell volume at equilibrium has increased, the solution is said to be hypotonic to the cell.
• If cell volume at equilibrium has decreased, the solution is said to be hypertonic to the cell.
• If cell volume at equilibrium has not changed, the solution is said to be isotonic to the cell. In other words,
• If the cell has a higher initial concentration of nonpenetrating solutes than the solution, at equilibrium water will have moved into the cell. The solution is hypotonic to the cell.
• If the solution has a higher initial concentration of nonpenetrating solutes than the cell, at equilibrium water will have moved out of the cell. The solution is hypertonic to the cell.
• If the cell and solution have equal concentrations of nonpenetrating solutes, at equilibrium there will be no net movement of water. The solution is isotonic to the cell.
There are several important points to keep in mind about tonicity:
• Tonicity has no units like mM or mosM. It is a comparative term that predicts changes in cell volume at equilibrium after exposure of the cell to a solution.
• By convention, we speak of the tonicity of a solution relative to a given cell. We never speak of the cell being hypo-/ hyper-/isotonic to the solution.
• With one exception, knowing only the osmolarity of the solution tells you nothing about the tonicity of the solution. The exception is that all hyposmotic solutions are hypotonic
. • Tonicity describes what has happened to cell volume at equilibrium but does not tell you what happens to cell volume on the way to equilibrium.
• It is important to be clear about the cell that is the frame of reference when discussing tonicity. Solutes that can enter one type of cell may not be able to enter a different type of cell. One example where this is true involves the disaccharide sucrose (table sugar). Mammalian cells do not have transporters for sucrose, so sucrose is a nonpenetrating solute for mammals. But plant cells do have sucrose transporters, making sucrose a penetrating solute for plants.

Hypo osmofio solution - with Jersey concentration of solution. (fresh water compared to salt wates) If a cell from a fresh water fish is placed into a beaker of salt water, the cell is se hypoosmotic to the water. Hyper osmotic solution with the greater concen -tration of solute (salt water compared to fresh water). If a cell from a salt water fish is placed in a beauer of freshwater, the cell is said to be hyper osmotic to the water. solutions of equal solution concen- Isoosmotic - -brations

6. Solution is hyposmotic to cells... So the solution is hypolonic to sell. by which is the only exception to the tonicity and osmolarity, discussion, where we can say that less number of active molecules. Cosmotic) in a solution makes it hypofonic to I the cell. Since, we do not know the concentration of the solutes we cannot say about isotomac or hypertonic reference, but in this case hypotonic. solution is confirmed. ② is solution A+ 5% Glucose (a penetrating solute hyperosmotic to the cells. - Tonicity? Answert W water molecules move faster through the cell membrane that particles of solute do. Therefore, a cell placed in a hyperosmotic solution will always shrink mitially, regardless of the solution's tonicity. Anite'ally the solution A was hypoesosmofes with 6% Glucose it becomes hyper osmotic but glucose is penetrable, so it can permeate the cell. - so it camot be hypertonic at equilibrium

(e) At equilibrium, solution At Glucose 5% can be either lactonic or hypotonic but not hyperionic. - (e) Solution A+ Glucose 5% cannot solely be hypotonic or isotonic as we are not Sodution to toga sure about concentration of solutes in solution A. and similarly, option (d) is not applicable. A muscle cell is kept in an iso osmotic. envirom ment with Dextrose + Nace. (0.45% (4 penetrable Non- penetrable. Assuming all solutes in cell are non- penetrable to cell membrane. Initially, the water movement will be nie due to isosmotic conditions Due to movement of dextrose (concentration unknown) water movement can be observed to a smaller extent When destrose moves into cell solution is hypoosmotic to cell and therefore must be hypotonic. So, water would move in tо hаѕ соu - Due to this, cell will increase in size at equilibrium . (6)