Term
| What percentage of the body is water weight, and what portion of that is intracellular vs. extracellular fluid? |
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Definition
50-60 percent of the bodies weight is water
Of that 50-60 percent, 2/3 is intracellular fluid and 1/3 is extracellular fluid |
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Term
| What 2 classes of molecules can passively pass through the bilayer? |
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Definition
1. Hydrophobic molecules
2. Small, uncharged, polar molecules
Note: Steroid hormones are a special type of large molecule that alter DNA activity that are hydrophobic and can pass through the bilayer |
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Term
| What is the difference between osmolarity and osmolality? |
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Definition
Osmolarity - moles of particles per LITER... cannot be measured, only calculated
Osmolality - moles of particles per KG solvent, can be measured by boiling point elevation or freezing point depression |
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Term
| Explain how solute concentration affects boiling point and freezing point |
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Definition
| Solutes only exist in the liquid state of the solvent, so the concentration of water (amount of water molecules per unit volume) is decreased in the liquid state because the solute particles are taking up space. This drives the equilibrium toward the water state, causing either gas to condense or ice to melt. In order to bring it back to its normal equilibrium, temperature must be lowered or raised. This causes the boiling/freezing point to alter. |
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Term
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Definition
| The pressure of the water crossing a barrier due to osmotic differences in the intra and extra cellular fluid composition |
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Term
| What is the osmolality of intracellular fluid in cells? |
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Definition
| 0.9% NaCl (330 milli-osmole) |
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Term
| What equation governs the change in volume of a cell in response to osmotic forces, and what is the assumption made in deriving this equation? |
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Definition
Vinit*OSMOLARITYinit = Vfinal*OSMOLARITYfinal
You assume that the extracellar Osmolarity does not change in response to water movement (Voutside>>>Vinside) |
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Term
| What are the steps involved in osmotic movement with both salts and urea present? |
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Definition
1. Transient response (only water moves to balance osmotic forces due to differences in Osmolarity)
2. Urea equilibrates across cell membrane such that urea osmolarity in and out of the cell are the same
3. Water changes direction again due to the new osmotic forces and reequilibrates |
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Term
| What is the difference between osmolality and tonicity? |
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Definition
osmolality is a property of a solution containing osmotically active particles
Tonicity is the ability of a solution to affect cell volume, and only impermeable solutes contribute to this |
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