3 Physiology: Water and Water Balance Flashcards
What percent of water is intracellular?
40%
How much of our body weight is water?
60%
What percent of water is extracellular?
20%
What percent of extracellular fluid is plasma?
4%
What percent is classified as “other” and what are they (the “others”)?
16%
1) interstitial fluid (fluid bathing cells)
2) lymph
3) epithelial and glandular secretions
4) aqueous
5) endolymph
6) peritoneal fluid
7) pleural fluid
8) pericardial fluid
9) CSF
10) renal filtrate
The volume, composition, and concentrations of solutes in all compartments are ideally kept within narrow limits.
See figure 1
What influences the degree to which various compartments differ from one another in volume, composition, and concentration of solutes?
Diffusion
Facilitated diffusion
Active transport
Formula for Concentration
(C)=mass/volume
therefore,
volume=mass/C
Formula for Flow
volume/time=flow=mass/(time)(C)
How much is a mole?
Mole=6.02 x 10^23
How many moles in a millimole?
millimole=1 x 10^-3 mole
Formula for Molar
Molar= Moles of Substance/Liter of Solution
Formula for Molal
Molal= Moles of Substance/Liter of H2O
Equivalent=Moles of charge
Formula for this?
Equivalent= (g of substance X)(valence of substance X)/Atomic or Molecular weight of substance X
Charged substances in a solution are called?
Electrolytes
What is a solution?
a homogeneous mixture of one or more substances (solutes) dispersed in a sufficient quantity of dissolving medium (solvent).
The solvent we will ALWAYS be concerned with is H2O.
What are Osmolytes?
Solutes that cause a depression in the freezing point and an elevation in the boiling point (colligative properties) of water.
What are some examples of Osmolytes?
Glucose
Na+
Cl-
Urea
What is a mole of Osmolyte called?
Osmol(e)
What can the concentrations of osmolytes be expressed as?
Osmolarity and Osmolality
Example 1 of osmolyte concentration
1 mole of glucose dissolved in 1 liter of H2O (1 molal glucose) is a 1 osmolal solution.
Molal= moles of substance/liter of H2O
Molal= 1 mole of glucose/ 1 liter of H2O
molal= 1 osmolal solution
Example 2 of osmolyte concentrations (know how to do calculations)
1 mole (=58 grams) of NaCl is added to 1 liter of H2O and the NaCl completely dissociates, there would be 1 mole of Na+ (=23 grams) and 1 mole of Cl- (=35 grams) in the i liter of H2O. The addition of 1 mole of glucose to this solution would yield the following concentrations: the solution is 1 molal Na+ the solution is 1 molal Cl- the solution is 1 molal glucose the solution is 3 osmolal the solution is 1 Eq/L Na+ the solution is 1 Eq/L Cl-
If an osmolyte cannot cross a membrane which allows the passage of H2O, what will occur?
Osmosis
What is osmosis?
is sometimes loosely defined as the diffusion of water through a selectively permeable membran
What happens when you add solute to a large volume of solvent?
it increases the percentage of molecular collisions between water molecules and solute species (IN REALITY, IT DOES NOT ALTER THE CONCENTRATION OF THE SOLVENT IN THE SOLUTION)
And if this occurs on one side of a membrane that does NOT allow passage of those solutes (but does allow passage of water), there will be more water-water collisions in the solution on the other side of the membrane, and therefore a net movement of water from that solution to the one with the greater concentration of impermeant solute.
(SO BASICALLY THIS IS THE DEFINITION OF OSMOSIS: THE MOVEMENT OF SOLVENT MOLECULES THROUGH A PERMEABLE MEMBRANE FROM A LOW SOLUTE CONCENTRATION INTO A REGION OF HIGH SOLUTE CONCENTRATION) (so water is going to move to where there is more solute and less water to try and equal it out)
Osmosis does NOT occur when?
does NOT occur in the absence of impermeant solute (substances that cannot cross membrane)
(solutes which can diffuse across membrane (ex. O2 and CO2) will achieve the same concentration on both sides of the membrane, which will result is solute-water collision of equal frequency on both sides of the membrane, so cause no osmosis) (this is because these solutes will move about the membrane to equal out instead of the liquid)
How might solutions be compared?
by concentrations of osmolytes
What is iso-osmotic solution?
a solution that has the same concentration compared to another solution
What is hypo-osmotic solution?
a solution with a lower concentration compared to another solution
What is hyperosmotic solution?
a solution with a higher concentration compared to another solution
An osmotically active solution is one which causes?
Osmosis (i.e. causes a net diffusion of water to it)
If an osmolyte CANNOT cross a membrane which allows the passage of H2O, it will exert what?
Osmotic Pressure