Lab 5: Osmolarity Flashcards
What is water important for?
Maintaining homeostasis- as a reservoir for hydration and dehydration reactions
What are the most common extra cellular fluids?
Blood plasma
Lymph
Interstitial fluid
(Water is a major component of all)
What are additional components to fluids?
Ions in the form of electrolytes and solutes
Predominant extra cellular electrocutes?
Sodium, chloride
Most predominant intracellular electrolytes?
Potassium
Phosphates
ATP
Proteins
What is osmosis?
Movement of water across a semi-permeable barrier
Purpose of osmosis?
To balance out concentration of solutes and water on either side of the semi permeable membrane (semi permeable membrane is permeable to water but not solutes)
How does water move from concentration wise?
From high water/low solute concentration to low water/high solute concentration (in order to balance two compartments)
What would happen is the semi-permeable barrier was permeable to the solute?
It would simply diffuse across
Does osmosis alter solution volumes on either side?
Yes
What is osmosis governed by?
The osmolarity of each of two solutions on either side of the semi permeable barrier
What does molar concentration need to be adjusted for?
The number of ions into which the solutes will dissociate, and the extent to which this occurs
What can we, therefore, define osmolarity or osmotic concentration as?
The number of molecules or ions per litre of solution
Equation for osmolarity?
(Osmotic coefficient: extent to which a compound will dissociate particularly in high concentration solutions)x( number of ions or molecules in to which the compound will dissociate in solution)x(molar concentration of the compound in solution)
How much of a compound will generally dissociate in water, in practice?
93% (instead of 100%)
What is isosmotic?
Two solutions with the same osmolarity
What is a solution with higher osmolarity than the other called?
Hyperosmotic
What is a solution with lower osmolarity than the other called?
Hyposmotic
What is osmotic pressure?
The greater the concentration, the greater the osmolarity of the solution, the greater the osmotic pressure, the greater the magnitude of water movement across the semi permeable membrane
What is the standard osmolarity of blood plasma?
280 mOsmol/L
What is intracellular fluid osmolarity compared to blood plasma under normal conditions?
The same
What does tonicity refer to?
The effect of intracellular and extra cellular (fluid) on cell volume
What happens when there’s equal osmolarity?
There will be no nett movement of water (no solute movement) and therefore no change in cell volume
What do we call no change in cell volume?
Isotonic
What would happen if the extra cellular fluid had lower osmolarity than the intracellular fluid?
Water would rush into the cell and cause it to swell
What is s solution that causes a cell to swell called?
Hypotonic
What percentage does a cell have to swell greater than its resting volume to burst (lyse)
40%
What would happen the the extra cellular fluid osmolarity increased to greater than the intracellular fluid?
The water would leave the cell and the cell would shrink (called crenation)
What is a solution that causes cell shrinking (crenation) called?
A hypertonic solution
Is osmolarity and tonicity always the same?
No- osmolarity is the number of dissolved ions/solutes, but tonicity is the effect
Why does urea explain the difference between osmolarity and tonicity?
It is isosmotic to intracellular fluids, but it can freely enter cells with water and causes a hypotonic result as it causes the cell to swell despite its isosomolarity
What are erythrocytes permeable to?
Water and some ions
What is the name of the volume of erythrocytes relative to total blood volume?
Blood haematocrit
What can a blood haematocrit identify?
Medical conditions such as anaemia and polycythemia
Average blood haematocrit of males vs females?
Males- 47%
Females- 42%
Was the process of cell washing used before this experiment?
Yes, so 99% of solution surrounding cells was an isotonic salt solution (plasma and WBC removed)
Volume concentration equation?
Moles/concentration
Moles equation?
Concentration x volume
What do you use to seal capillary tubes?
Critoseal
What is used to separate erythrocytes from NaCl solution?
Centrifuge (3700 revolutions per minute)
In a capillary tube, what vindicates a burst (lyse) cell?
The whole tube being light pink
Dilution factor equation?
Final volume/original volume
