Water determines the structure and biological properties of:
Proteins, Nucleid acids, Lipids, biological membrane
Water has a tendency to inoize into?
Ionize into hydrogen and hydroxyde ions. This ionization is crucial to waters role in cellular function. The amount of hydrogen and hydroxide ion in a solution is: (H+) x (OH-) = 10^-14 mol/l
pH in water?
- In pure water, there is one hydrogen ion for every hydroxide ions, so they are both equal 10^-7 mol/l. - as pH = -log (H+), in pure water pH =7
Claude Bernard stated:
Life is an expression of the physical reality and the maintenance of life is guaranteed by the constancy of the fluid matrix or "milieu interieur"
Walter Bradford Cannon stated:
Stability of internal environment = Homeostasis
Fluid compartments in the Body:
Total Body Fluid:
- Intracellular fluid (ICF)
-Extracellular Fluid (ECF):
- Interstitial fluid (ISF), Intravasal fluid (IVF), Trancellular fluid (TCF)
Comprises 2/3 of the bodys water. It is primarly a solution of potassium and organic anions, proteins etc. The cell membranes and cellular metabolism control the constituents of this ICF.
Extracellular fluid (ECF)
Is 1/3 of the bodys water. ECf is primarly NaCl and NaHCO3 solution. It is further subdivided into: - Interstitial fluid (surrounds the cells, but does not circulate. 3/4 of ECF) - Intravasal fluid IVS (blood plasma, circulates as the extracellular components of blood. 1/4 of ECF) - Transcellular fluid TCF (set of fluid that are outside of the normal compartments, 1-2%. Cerebrospinal fluid in the CNS, aqueous humor and vitreous humor, synovial fluid in the joints, glandular secretion, serous fluid etc)
Components of homeostasis
Isovolemia, isosmosis, isoinoia, isohydria
The constancy of the volume of ECF
decreased volume of ECT, less than 20%
Increased volume of ECF, more than 20%
decreasedvolume of blood plasma
increased volume of blood plasma
increased volume of ISF
The constancy of the osmotic pressure of ECF
Osmotic pressure depends on?
the number of solute particles per unit volume = osmotic concentration (osmolarity)
Difference between Isosmotic and Isotonic?
For an isosmotic solution to be isotonic, the membrane must be equally impermeable to all solutes. - All isotonic solution are isosmotic! - But not all isosmotic solutions are isotonic!
The constancy of the pH of ECF
pH of ECF=
pH in blood =
-log 2.5 x 10^-7 = 7.4 (7.35-7.45)
pH is acidosis when?
it is between 7.35-7.0
pH is alkalosis when?
it is between 7.45 and 7.8
Acid-base balance is regulated by:
Acid-base buffer systems, respiratory centers in the brain ste and the kidneys
Buffer systems or buffer pairs tend to....?
reisits change in pH, when H+ or OH- is added
What is buffer capacity?
it is a measure of the efficiency of a buffer in resting changes in pH. Conventionally, the buffer capcaity is expressed as the amount (mol) of strong acid or base, that must be added to 1 liter of the solution to change its pH by one unit.
Bicarbonate buffer system:
mainly in ECF
Phosphate buffer system:
Mainly in ICF
Protein buffer system:
in plasma and ICF
Hemoglobin buffer system: