Acid base

1. ACID-BASE
BALANCE
By
Dr Sajad Ahmad

2. Acids & Bases
Acids:
acids are sour tasting
Arrhenius acid: Any substance that, when dissolved
in water, increases the concentration of hydronium
ion (H3O+)
Bronsted-Lowry acid: A proton donor
Lewis acid: An electron acceptor
Bases:
bases are bitter tasting and slippery
Arrhenius base: Any substance that, when dissolved
in water, increases the concentration of hydroxide
ion (OH-)
Bronsted-Lowery base: A proton acceptor
Lewis acid: An electron donor

3. Acids & Bases
STRONG vs WEAK
_ completely ionized _ partially ionized
_ strong electrolyte _ weak electrolyte
_ ionic/very polar bonds _ some covalent bonds
Strong Acids: Strong Bases:
HClO4 LiOH
H2SO4 NaOH
HI KOH
HBr Ca(OH)2
HCl Sr(OH)2
HNO3 Ba(OH)2

4. pH
A measure of the hydronium ion
• The scale for measuring the hydronium ion concentration [H3O+]
in any solution must be able to cover a large range. A logarithmic
scale covers factors of 10. The “p” in pH stands for log.
• A solution with a pH of 1 has [H3O+] of 0.1 mol/L or 10-1
• A solution with a pH of 3 has [H3O+] of 0.001 mol/L or 10-3
• A solution with a pH of 7 has [H3O+] of 0.0000001 mol/L or 10-7
pH = - log [H3O+]

5. The pH scale
The pH scale ranges from 1 to 10-14 mol/L or from 1
to 14.
pH = - log [H3O+]
1 2 3 4 5 6 7 8 9 10 11 12 13 14
acid neutral base

6. INTRODUCTION
• pK/ pKa
– Negative log of the ionization constant of an
acid
– Strong acids would have a pK <3
– Strong base would have a pK >9
• pH
– Negative log of the hydrogen ion
concentration
– pH= pK + log([base]/[acid])
– Represents the hydrogen concentration

7. • Buffer
– Combination of a weak acid and /or a weak
base and its salt
– Mixture of compounds which have the ability
to absorb small amounts of H+ or OH- with
very little change of pH or no change at all.
– They resist change in pH

8. REGULATION OF PH
• Direct relation of the production and retention of
acids and bases
• Systems
– Respiratory Center and Lungs
– Kidneys
– Buffers
• Found in all body fluids
• Weak acids are good buffers
• Strong acids are poor buffers

9. BUFFER SYSTEMS
• Why do we need them?
– If the acids produced in the body from the
catabolism of food and other cellular
processes are not removed or buffered, the
body’s pH would drop
– Significant drops in pH interferes with cell
enzyme systems.

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11. BLOOD BUFFER SYSTEMS
Major Buffer Systems
– Protein Buffer systems
• Amino acids
• Hemoglobin Buffer system
– Phosphate Buffer system
– Bicarbonate-carbonic acid Buffer system

12. BLOOD BUFFER SYSTEMS
Protein Buffer System
– Originates from amino acids
• ALBUMIN- primary protein due to high
concentration in plasma
– Buffers both hydrogen ions and carbon
dioxide

13. BLOOD BUFFERING SYSTEMS
Hemoglobin Buffer System
• Binds CO2
• Binds and transports hydrogen and oxygen
• Maintains blood pH as hemoglobin
changes from oxyhemoglobin to
deoxyhemoglobin

14. BLOOD BUFFER SYSTEMS
Phosphate Buffer System
• Has a major role in the elimination of H+ via
the kidney
• Essential within the erythrocytes

15. BLOOD BUFFER SYSTEMS
Bicarbonate/carbonic acid buffer system
– Function almost instantaneously
– Cells that are utilizing O2, produce CO2, which
builds up. Thus, more CO2 is found in the
tissue cells than in nearby blood cells. This
results in a pressure (pCO2).
– Diffusion occurs, the CO2 leaves the tissue
through the interstitial fluid into the capillary
blood

16. Henderson-Hasselbalch
Equation
• Relationship between pH and the
bicarbonate-carbonic acid buffer
system in plasma
• Allows us to calculate pH

17.  General Equation
pH = pK + log [Base]
[Acid]
 Bicarbonate/Carbonic Acid system
pH= pK + log HCO3
H2CO3
• The ratio of HCO3
- (salt) to H2CO3 ( acid) is normally
20:1

19. PHYSIOLOGICAL BUFFER SYSTEM
• Lungs/respiratory
– Quickest way to respond, takes minutes to
hours to correct pH
– Eliminate volatile respiratory acids such as
CO2
– Body pH can be adjusted by changing rate
and depth of breathing
– Provide O2 to cells and remove CO2

20. PHYSIOLOGICAL BUFFER SYSTEM
• Kidney/Metabolic
– Can take several hours to days to correct pH
– Most effective regulator of pH
– Can eliminate large amounts of acid
– Can excrete base as well
– If kidney fails, pH balance fails

21. ACID-BASE
BALANCE
DISORDERS

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23. ACID-BASE BALANCE DISORDERS
ACIDOSIS
respiratory metabolic
ALKALOSIS
respiratory metabolic

24. RESPIRATORY ACIDOSIS (RAc)
RAc is caused by hypoventilation (or breathing of
CO2 containing air). Hypoventilation is associated
with an impaired ability to eliminate CO2, whereby
pCO2 increases and the accumulated CO2 reduces
the arterial pH.
CAUSES:
airway obstruction, neuromuscular disorders,
disorders of CNS, opiate poisoning

25. RESPIRATORY ALKALOSIS (RAl)
The hyperventilation is disproportionately high
compared to the CO2 production, whereby the pCO2
falls and the pH increases
CAUSES:
CNS injury, Pregnancy, Anxiety, Fever, cerebral
disease, anxious patient during an attack of asthma.

26. Metabolic acidosis (MAc)
● MAc is caused by accumulation of acids in ECF.
CAUSES:
• hypoxia is a lack of O2 in tissues → anaerobic
glycolysis produces lactic acid → lactate acidosis
• overproduction of ketone bodies → ketoacidosis

27. METABOLIC ALKALOSIS (MAl)
MAl is caused by a primary accumulation of
bases in ECF
CAUSES:
• ingestion of alkaline drugs (e. g. NaHCO3)
• prolonged vomiting → loss of H+

28. THANK
YOU