Mod.A. Bio Lec2:Homeostasis of pH Flashcards
pH
measure of The acidity or alkalinity of a
solution
Acid
is a substance that acts as a
H+ (proton) donor
Base
is a substance that combines
with a H+ i.e. H+ acceptor
OR : substances which produce
hydroxyl ions
The homeostasis of the body fluids at a Normal arterial blood pH is between :
7.35-7.45
If blood pH moves to much below 6.8 or above 7.8,
cells stop functioning and the patient dies
The more H+ conc.
the more acidic the solution and the LOWER the pH
The lower H+ conc.
the more alkaline the solution and the HIGHER the pH
Sources of Hydrogen Ion
1-Metabolism of carbohydrates and fats Produce CO2 (volatile acid)
2-metabolism of protein
التي تحتوي AA S أي
تنتج sullfer على
sulphuric acids
3-metabolism of
phospholipids
تنتج
phosphoric acid
Types of acids: (2)
VOLATILE ACIDS. FIXED ACIDS
Volatile acids:
Produced by oxidative metabolism
of CHO, Fat, and Protein.
Excreted through LUNGS as CO₂
gas
Fixed acids:
Acids that do not leave solution, once produced they
remain in body fluids until eliminated by KIDNEYS
E.g. Sulfuric acid, phosphoric acid, and organic acids
are most important fixed acids in the body
Why Is Normal pH Essential?
1-Maintain Body hemostasis Enzyme activity
2-Acid destroys cell membranes مثال : Lactate acid can destroy the cell membrane
3- Alteration of K+ levels. and Delivery of O2
Acidosis:
Physiological state resulting from
abnormally low plasma pH
–Too much acid –Too little base
–Acidemia: plasma pH < 7.35
Alkalosis:
Physiological state resulting from
abnormally high plasma pH
–Too much base –Too little acid
–Alkalemia: plasma pH > 7.45
Rates of Compensation : 3
1•Buffers function almost instantaneously
2•Respiratory compensation take several minutes
3•Renal compensation may take several hours to days
Buffer Systems
Is the systems that maintain a normal pH or resist changes in pH.
يعتبر* :First line of defense
مدة عمله * : act instantaneously short-term solution to the problem of excess H+.
Most important buffers are :4
1-bicarbonate
2-phosphate
3-protein
4-ammonia
most important
Extracellular buffer
bicarbonate
a buffer is made up of
two compounds, called a buffer pair.
1- one of the pair is an acid 2- the second of the pair is a base
Bicarbonate buffer system:
Most important buffer system in the plasma
• Buffer all fixed acid, but not volatile acid
• Buffer capacity is strong
مكان عمله * : in all tissues that contain carbonic anhydrase
(found mainly in erythrocytes and kidneys.).
Phosphate buffer system:
1-not found in high concentrations in all tissues. 2-Its concentration in plasma is very low. 3-It is mainly an intracellular buffer and a renal tubular buffer.
This buffer system consists of :
weak acid
1-dihydrogen phosphate ions (H2PO4
as hydrogen-ion donor
base
2-hydrogen phosphate ions (HPO4
as hydrogen-ion acceptor
Most important buffer system in body cells.,Also in the blood. ?
protein buffer system
in albumin:
16 histidine -
buffer in plasma.
in hemoglobin:
38 histidines -
buffer in the RBC’s.
Steps of Hb buffer system:
1- : CO2 diffuses across RBC membrane
2- As carbonic acid dissociates : يتكون
Bicarbonate ions diffuse into plasma Hydrogen ions are buffered by hemoglobin molecules
The lung regulates the ratio of [HC03
-]/[H2CO3] to approach
20/1
The respiratory buffering system uses
bicarbonate
how does the respiratory buffering system work:
Eliminate or Retain CO₂ (controls CO2 levels )
Hyperventilation :
leads to loss of CO2 and creates
alkaline conditions
Hypoventilation:
leads to retain of CO2 creates
acid conditions
The renal buffer system uses
bicarbonate, phosphate and ammonium.
Normal pCO2 level
35-45
Normal HCO3 level
22-28
Primary problems with C02 excretion are reflected in PC02;
these are called
Respiratory
Primary problems with hydrogen ion production or excretion
are reflected in the [HC03-] and these are called
Metabolic
