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Chapter-21 Acid-Base, pH, Electrolyte and Water Balance

BOOK TITLE: Textbook of Biochemistry for Dental Students

Author
1. Vasudevan DM
2. S Sreekumari
3. Vaidyanathan Kannan
ISBN
9789350254882
DOI
10.5005/jp/books/11333_21
Edition
2/e
Publishing Year
2011
Pages
8
Author Affiliations
1. Faculty of Medicine, Amrita Vishwa Vidyapeetham, (Amrita University), Kochi, Kerala, Formerly Principal, College of Medicine, Amrita, Kerala; Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, Amrita Vishwa Vidyapeetham (Deemed University), Cochin, Kerala, E-mail: dmvasudevan@aims.amrita.edu, PG Programs and Research College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India, College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India; Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, India
2. Jubilee Mission Medical College, Trissur, Kerala, Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India, Government Medical College, Thrissur and Thiruvananthapuram, Kerala, India; Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India; Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
3. Amrita Institute of Medical Sciences, Kochi, Kerala, India, Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, India, Believers Church Medical College and Hospital, Thiruvalla, Kerala, India
Chapter keywords

Abstract

Acids are capable of donating protons. Strong acids dissociate completely. Weak acids ionize incompletely. Acidity of a solution is measured by noting the hydrogen ion concentration. The pH is inversely proportional to acidity. Neutral pH is 7. Buffers are solutions which can resist changes in pH when acid or alkali is added. Buffers can be made by mixtures of weak acids with their salt with a strong base. The pH of buffer is calculated by the Henderson-Hasselbalch equation. Most important buffer system in plasma is the bicarbonate-carbonic acid system. Bicarbonate represents the alkali reserve. Normal bicarbonate level in plasma is 24 mmol/L main intracellular buffer is phosphate buffer. First defense against acid entry into blood is by bicarbonate buffer system. Second defense against acid is by respiratory regulation of pH. Third defense system is the renal regulation. Renal regulation has 3 components: 1. Excretion of hydrogen ion, 2. Na+/ H+ exchange, and 3. excretion of ammonium ions. Respiratory acidosis means primary excess of carbonic acid. Metabolic acidosis means primary deficiency of bicarbonate. Respiratory alkalosis is primary deficiency of alkali. Metabolic alkalosis means primary excess of bicarbonate. The major factors controlling the water intake are thirst and the rate of metabolism. The renal function is the major factor controlling the rate of output of water. Albumin is mainly responsible in maintaining the osmotic balance intravascularly. Osmolality of plasma varies from 285 to 295 mOsm/ kg. It is maintained by the kidney which excretes either water or solute as the case may be. Regulation of sodium and water balance is by the hormones (aldo­sterone, ADH) and the renin-angiotensin system.

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