The document discusses two major buffer systems in the body: 1) The bicarbonate/carbonic acid buffer system is the major plasma buffer. It works to neutralize acids produced from carbon dioxide through the reaction of CO2, H2O and bicarbonate ions. It is regulated by the respiratory and urinary systems. 2) The phosphate buffer system is the major buffer in urine and uses hydrogen phosphate and monohydrogen phosphate ions. It has less total buffering power than the bicarbonate system but works to buffer the kidney filtrate and excrete excess acid or base without altering urinary pH.

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

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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

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