buffers

1. BUFFERS
By
Mehreen roohi

2. LEARNING OBJECTIVES:
BY THE END OF THIS LECTURE YOU WILL
BE ABLE TO:
Define buffers
Define pH
Describe different types of buffers
Describe bicarbonate buffer and phosphate
buffer.

5. BODY BUFFER SYSTEMS
 bicarbonate/carbonic
acid
 major plasma buffer
 phosphate: H2PO4- /
HPO42-
 major urine buffer
 ammonium: NH3 / NH4+
 also used to buffer the
urine
 proteins: important in ICF
 Hb: is the main buffer
against CO2 changes

6. BICARBONATE BUFFER SYSTEM
 Carbonic acid (H2CO3)
 Weak acid
 Bicarbonate ion (HCO3
-)
 Weak base
 CO2 + H20  H2CO3  H+ + HCO3
-

7.  Works along with respiratory and urinary system
These systems remove CO2 or HCO3
-
THE RATIO OF BICARBONATE TO CARBONIC ACID IS
NORMALLY 20:1
Alterations in the ratio alters Ph irrespective of absolute
concetrations

8. *Image via Bing

9. NaOH + H2CO3 H2O + NaHCO3
HCl + Na HCO3 NaCl + H2CO3

10. BICACARBONATE
BUFFER

11. *Image via Bing

12.  The most powerful extracellular
buffer in the body
 The two elements of the buffer
system are regulated by the
kidneys and the lungs

17. PHOSPHATE BUFFER SYSTEM
Dihydrogen phosphate ion (H2PO4
-)
Weak acid
Monohydrogen phosphate ion (HPO4
2-)
Weak base
H2PO4
-  H+ + HPO4
2-
More important in buffering kidney filtrate than in tissue

19. PHOSPHATE BUFFER SYSTEM
The main elements of the phosphate buffer system are
H2PO4- and HPO4
NaOH + NaH2PO4 H2O+ Na2HPO4
HCl + Na2HPO4 NaCl + NaH2PO4

20.  pK 6.8
 8 % of the concentration of the bicarbonate buffer
 The total buffering power less than that of the bicarbonate
buffering system.
 Works totally in conjunction with the kidney
 Excretes the excess acid or base without any alteration in urinary
pH

21. *Image via Bing