Can restore normal ph fast milliseconds buffer system

Can restore normal pH FAST - milliseconds
Buffer system composed of weak acid and weak
base
3 major chemical buffers in the body:
Bicarbonate system
Phosphate system
Protein system
The amount of acid or base neutralized depends on
concentration of buffer and pH of working
environment

24-58
Bicarbonate Buffer System
a solution of carbonic acid and bicarbonate ions
Carbonic acid and bicarbonate ions participate in a
reversible reaction
CO
2
+ H
2
O  H
2
CO
3
 HCO
3
−
+ H
+
Direction of reaction determines whether it raises or lowers pH
CO
2
+ H
2
O  H
2
CO
3
 HCO
3
−
+ H
+
Lowers pH by releasing H
+
CO
2
+ H
2
O  H
2
CO
3
 HCO
3
−
+ H
+
Raises pH by binding H
+
integrated with lungs & kidneys to regulate pH and CO
2
- to lower pH, kidneys excrete HCO
3
−
& lungs retain CO
2
- to raise pH, kidneys excrete H
+
& lungs excrete CO
2

24-59
Phosphate Buffer system
a solution of HPO
4
2−
and H
2
PO
4
−
H
2
PO
4
−
 HPO
4
2−
+ H
+
Reactions that proceed to the right liberate H
+
and  pH,
and reactions that proceed to the left will  pH
Phosphates are important buffers in ICF and renal tubules
Protein Buffer System
Proteins , more concentrated than bicarbonate or phosphate
systems, especially in the ICF
accounts for ~3/4 all chemical buffering in body fluids
Protein buffering ability due to side groups of amino acid residues
 pH  carboxyl (−COOH) groups release H
+
when pH gets too low, amino (−NH
2
) groups bind H

24-60
Respiratory Control of pH
Strong buffering capacity due to bicarbonate buffer system
CO
2
+ H
2
O  H
2
CO
3
 HCO
3
-
+ H
+
addition of CO
2
to body fluids   H
+
, lowering pH
removal of CO
2
  H
+
, raising pH
Respiratory system neutralizes 2-3X more acid v. chemical buffers
Chapter 22 ...
CO
2
is constantly produced by aerobic metabolism,
and normally eliminated by the lungs at an equivalent rate
 CO
2
and  pH  stimulate pulmonary ventilation,
whereas  pH inhibits pulmonary ventilation
CO
2
from metabolism + H
2
O  H
2
CO
3
 HCO
3
−
+ H
+
Lowers pH by 'releasing' H
+
CO
2
expired + H
2
O  H
2
CO
3
 HCO
3
−
+ H
+
Raises pH by 'binding' H
+

24-61
Renal Control of pH
Kidneys neutralize more acid or base than either the
respiratory system or chemical buffers
Renal tubules secrete H
+
into tubular fluid & excrete

Most H
+
binds to bicarbonate, ammonia, and phosphate buffers

Bound and free H
+
excreted in urine, i.e., H
+
expelled from body
 Other buffer systems  H
+
concentration by binding H
+

Secretion and Neutralization of H + by the Kidney
K
+
Na
+
NaHCO
3
HCO
3
–
Na
+
Urine
Carbonic
Anhydras
e
CO
2
Aerobic Respiration
Na
+
HCO
3
–
+
CO
2
–
H
2
CO
3
H
2
CO
3
H
2
O
Antiport
Diffusion thru
channel
Diffusion thru
lipid
membrane
Key
+
CO
2
2
1
8
5
10
11
6
7
9
4
3
1
In blood:
H
+
+ HCO
3
–
 H
2
CO
3
2 H
2
CO
3
 H
2
O + CO
2
,
which enter the tubule cell
3
4
Carbonic Anhydrase
combines
H
2
O + CO
2
to re-form H
2
CO
3
5
H
2
CO
3
 HCO
3
–
+ H
+
;
HCO
3
–
returns to blood
6
Na
+
-H
+
antiport
exchanges H
+
for Na
+
7
from glomerular filtrate
NaHCO
3
 Na
+
+ HCO
3
–
;
Na
+
transported into tubule cell
8
Na
+
leaves cells by Na
+
-pump
at basolateral side  into blood
9 HCO
3
–
+ H
+
from tubule
 H
2
CO
3
10
At brushborder, H
2
CO
3
 H
2
O + CO
2