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A) Calculate the osmolarity of the cell. 15 0SA B) Calculate the osmolarity of t

ID: 3511701 • Letter: A

Question

A) Calculate the osmolarity of the cell. 15 0SA B) Calculate the osmolarity of the solution: 30 osm C) The solution is Cell Solution 15 mM NaCI 15 mM Urea to the cell. hyperosmotic b) isoosmotic c) hyposomotic 15 mM Dextrose IMPORTANT NOTE: Osmolarity does not differentiate between penetrating solutes (can diffuse across a membrane) and non-penetrating solutes (cannot or does not diffuse across a membrane). In contrast, tonicity only takes into account non-penetrating solutes. 6) Name a non-penetrating solute to a human red blood cell 7) Provide a mechanical explanation for this paradox: Simple sugars can be a penetrating solute for human cells.

Explanation / Answer

Osmolarity = z × Molarity (z = total number of ions formed by dissolution of a substance).

A. Molarity of NaCl = 15 m M and NaCl dissociate into 2 ions Na+ and Cl- so Z for NaCl = 2. So Osmolarity of 15 m M NaCl = 2 × 15 = 30 mOsm.

B. Osmolarity of solution = Osmolarity of 15 m M urea + Osmolarity of 15 m M Dextrose.

C. The solution is hyperosmotic.

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