Blood buffer

The blood buffer is the very complex buffer system of the blood , which buffers the pH value of the blood within narrow limits. It is part of the acid-base balance . The pH constancy is essential for all organisms. The set pH value for mammals is 7.4 on average. In humans, the pH is in the range 7.35–7.45. If the pH value is lower, it is called acidosis , if it is higher, it is called alkalosis .

Buffer systems in the blood

The blood buffer is created by the interaction of four buffer systems in the blood. The four mammalian blood buffers in decreasing buffer capacity are:

• Carbonic acid-bicarbonate system ( carbonic acid - hydrogen carbonate buffer) (53% of the total buffer capacity of the blood, catalyzed by the enzyme carbonic anhydrase ):

${\displaystyle \mathrm {CO_{2}+2\ H_{2}O\ \rightleftharpoons \ H_{2}CO_{3}+H_{2}O\ \rightleftharpoons \ H_{3}O^{+}+HCO_{3}^{-}\ } }$

• Hemoglobin (35% of the total buffer capacity of the blood): In the oxygen cycle, the hemoglobin acts as a buffer:

${\displaystyle \mathrm {Hb\cdot H^{+}+H_{2}O\ \rightleftharpoons \ H_{3}O^{+}+Hb} }$

• Proteinate buffer (around 7% of the total buffer capacity of the blood): Plasma proteins (especially albumin ) act as buffers because of their amphoteric character.

• Phosphate buffer (5% of the total buffer capacity of the blood, is of great importance intracellularly):

${\displaystyle \mathrm {H_{2}PO_{4}^{-}+H_{2}O\ \rightleftharpoons \ H_{3}O^{+}+HPO_{4}^{2-}} }$

Individual evidence

1. ↑ Winfried Ahne: Zoology: textbook for students of veterinary medicine and agricultural sciences . Schattauer Verlag, 2000, ISBN 978-3-7945-1764-0 , p. 137
2. ^ PT Marshall: The Physiology of Mammals and Other Vertebrates: A Text Book for High Schools and Colleges . Birkhäuser-Verlag, reprint 2013, ISBN 978-3-0348-5964-6 , pp. 121f

literature

Internal medicine: reference work for specialists, edited by Wolfgang Gerok, 11th edition, 2007, Schattauer Verlag GmbH, ISBN 978-3-7945-2222-4