Molarity vs Molality
Molarity: Moles of substances per litre of the solution.
Molality: Moles of substance per kg of solvent
Osmolarity vs Osmolality
Osmolarity: osmoles per litre of solution
Osmolality: Osmoles per kg of solvent
Some molecules liberate more than one particle in solution. NaCl vas Na2so4.
Osmosis: Movement of water to a semi-permeable membrane from a compartment in which solute conc is lower to one which is higher.
I.e low osmoses to higher osmoses.
Osmotic pressure is pressure needed to stop water movement of osmosis.
1.1 Van't Hoff's Law
osmotic pressure = number of dissociable particles/molecues X Total solute concentration X Gas Constant X Absolute Temperature.
1.2 Comparing Solutions
Tonicity of a solution depends on the osmolarity concentration and whether the solute can permeate the cell.
Permeant solutes, it is different.
For example, with the same amount of solute i.e Nacl and urea.
NaCl has a pump so it pumps out stuff, so there's like no change.
Whereas, urea, it goes into the cell, so the water also gets into the cell to maintain tonicity.
1.2.2 Colloid osmotic pressure
Also known as oncotic pressure, it si the pressure exerted by proteins and other cations.
2 Volume of Body Fluid Compartments
Typical 70kg man consists of water, proteins and related substances, mineral Fats.
Total body water varies with age (young more, old less)
Obesitity and women, i.e more fat more water storage.
3 Measurement of Volumes
Indicator Dilution Technique:
V = Q/c
Q= amount injected - amount lost
More changes in intracellular content due to loads of proteins.
Plasma electrolyte composition is controlled by kidney.
Plasma vs Interstitial fluid composition is maintained by:
Capillaries that thens to hold protein
Extracellular vs intracellular:
Selective ion pumps
Total body water is controlled by thirst, kidney and ADH.
Regulates: water and electrolyte balance, acid-base balance
Excretion: Metabolic waste products, foreign chemicals and other bioactive substances.
Regulate: Arterial BP, RBC production, VIt D and gluconeogenesis.