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ACID BASE BALANCE BY DR. VENKATA.pptx
1. DR. VULLI VENKATA RAO Ph.D.(Medical
Biochemistry)
SENIOR LECTURER
DEPARTMENT OF BIOCHEMISTRY
ACID BASE BALANCE
2. Objectives.
■ Concept of Acid & base.
■ pH and H ion concentration.
■ Handerson-Hasselbalch equation.
■ Mechanisms to maintain acid base balance.
■ Applied aspects.
Saturday, April 18, 2015
3. ACIDS
❑ Acids are the substances which can donate
H+ ion (proton).
❑These are hydrogen containing substances
which can dissociate in soln. to release H+.
❑Not all hydrogen containing substances are
acids; e.g. Carbohydrate.
H+
HCl + Cl-
4. ACIDS
❑ Types of acids in the body:
1. Volatile Acids:
➢Can leave the solution and enter the
environment.
➢H2CO3 is the only volatile acid in the body.
2. Non-Volatile Acids (Fixed Acids/Metabolic
Acids):
➢Acids that do not leave the solution.
➢All other acids in the body.
➢Ex: Pyruvic acid, Lactic acid, Phosphoric acid
etc.
H2CO3 H2O + CO2
5. ACIDS
❖ Physiologically important acids:
❖Carbonic acid (H2CO3)
❖Phosphoric acid (H3PO4)
❖Pyruvic acid (C3H4O3)
❖Lactic acid (C3H6O3)
❖ These acids are products of various
metabolisms in the body.
❖ Dissolved in body fluids.
6. BASE
➢
➢ Bicarbonate (HCO3
-)
Biphosphate (HPO4 )
-2
❑
Base is a substance which can
accept H+ ion (proton).,e.g. Hydroxyl
ion (OH-).
OH- +H+ H2O
■Physiologically important bases:
7. Alkali
❑ Used synonymously with base.
❑ Molecule formed by combination of an
alkaline metal (Na,K,Li) with a highly basic ion.
➢ Ex- NaOH, KOH, NaHPO4
❑ Base portion of these molecules react quickly
with H+to remove these from solution, i.e.
alkalis act as typical bases.
NaOH
+ H+
Na+ + OH-
H2O
8. Acids & Bases can be classified as strong or weak
acid/base
■ Strong acid/base:
■ One that dissociates completely in a solution.
■ Ex: HCl, H2SO4, NaOH
■ Weak acid/base:
■ One that dissociates partially in a solution.
■ Ex: H2CO3,
HCl
NaOH
H+ + Cl-
Na+ + OH-
H2CO3
H+ + HCO3-
10. pH:potential of hydrogen
The letters pH stand for potential of
hydrogen, since pH is effectively a measure
of the concentration of hydrogen ions (that is,
protons) in a substance.
11. PH SCALE
❑ Normal blood pH is 7.35 - 7.45
❑ pH range compatible with life is 6.8 - 8.0
pH = - log H+ concentration
pH = 7.4
The pH is a measure of the concentration of hydrogen ions,
the acidity or alkalinity of a solution. The pH-scale is normally
between 0 and 14.
13. 29-Nov-22 Acid Base Balance
13
Normal H+
Concentration
Because of low H+ conc in body
fluids
H+ concentration
Customarily expressed on
logarithm scale
Using pH units
pH = log (1/[H+]) = -log[H+]
14. 29-Nov-22 Acid Base Balance
14
Normal H+
Concentration
With a normal [H+] = 40 nEq/L =
0.00000004 Eq/L
pH = -log[0.00000004]
pH = 7.4
Thus pH is inversely related to [H+]
Low pH corresponds to high [H+]
High pH corresponds to low [H+]
15. ❑ Normal blood pH is 7.35 - 7.45
❑ pH range compatible with life is 6.8 - 8.0
16. PH SCALE
pH = - log [H+] pH = log 1/
[H+]
❑ pH is inversely related to H+concentration. low pH –
indicates high H+concentration. high pH –
indicates low H+concentration.
❑pH = 4 has 10 times more free H+concentration than pH = 5
and 100 times more free H+concentration than pH = 6
❑pH range from 1-14.
pH < 7 – Acidic pH
> 7 – Basic pH
7 - Neutral
17. PH of the ECF is regulated very precisely
ACIDOSIS ALKALOSIS
NORMAL
DEATH DEATH
Venous
Blood
Arterial
Blood
7.3 7.4 7.5
6.8 8.0
18. EFFECTS OF pH change
■ pH changes have dramatic effects on normal cell
function
■ 1) Changes in excitability of nerve and muscle
cells
■ 2) Influences enzyme activity
■ 3) Influences K+levels
18
19. Changes in cell excitability
■ pH decrease (more acidic) depresses the central
nervous system
■ Can lead to loss of consciousness
■ pH increase (more basic) can cause over-excitability
■ Tingling sensations, nervousness, muscle twitches
pH Excitability
pH Excitability
19
20. Influences on enzyme activity
■ pH increases or decreases can alter the shape
of the enzyme rendering it non-functional
■ Changes in enzyme structure can result in
accelerated or depressed metabolic actions
within the cell
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21. ACID BASE BALANCE
■
■ pH maintenance means maintaining [H+].
■ This involves two important ions which are regulated by
various chemical & physiological process:
H+
HCO3
-
22. 29-Nov-22 Acid Base Balance
22
Henderson
Hasselbach
Equation
pH = pKa + log(Base)/(Acid)
This is the Henderson-Hasselbach
equation
