Water, Acids, Bases, and Buffers | Chapter 4 - Marks' Basic Medical Biochemistry
Chapter 4 of Marks' Basic Medical Biochemistry: A Clinical Approach (5th Edition) explores the fundamental role of water and buffer systems in maintaining homeostasis and protecting cells from dangerous fluctuations in pH. The chapter begins by describing how approximately 60% of body weight is water, distributed between intracellular and extracellular compartments, and how the dipolar nature of water enables hydrogen bonding, solvent capacity, and thermal regulation. It explains osmolality, osmotic pressure, and the movement of water between compartments, showing how dehydration, osmotic diuresis, and intravenous saline infusion affect fluid balance. The chemistry of acids and bases is introduced through dissociation constants (Ka), strong versus weak acids, and the Henderson–Hasselbalch equation, which relates pH, pKa, and dissociation. Buffers, composed of weak acids and conjugate bases, are presented as key systems that resist pH changes, with special emphasis on the bicarbonate buffer system, hemoglobin buffering in red blood cells, and phosphate and protein buffers in intracellular environments. The chapter discusses how normal metabolism generates acids such as lactic acid, ketone bodies, sulfuric acid, and carbon dioxide, and explains how respiratory and renal systems excrete acid via CO₂ expiration and urinary hydrogen, ammonium, and phosphate ions. Clinical case studies reinforce biochemical principles: Dianne A., a patient with type 1 diabetes mellitus, develops diabetic ketoacidosis with hyperglycemia, ketone body accumulation, osmotic diuresis, and Kussmaul respiration; Dennis V., a child who ingested aspirin, demonstrates how salicylate toxicity causes respiratory alkalosis followed by metabolic acidosis; and Percy V. presents anxiety-induced hyperventilation and respiratory alkalosis. Biochemical comments highlight dehydration mechanisms, the role of electrolytes like Na⁺, K⁺, Cl⁻, and HCO₃⁻, and how buffer systems integrate with organ physiology. The chapter concludes with a discussion of gastric hydrochloric acid, renal ammonium excretion, and the diagnostic use of blood gases, pH measurements, and HbA1C in diabetes, emphasizing how water, acids, bases, and buffers are central to both normal physiology and disease states. 📘 Read full blog summaries for every chapter: https://lastminutelecture.com 📘 Have a book recommendation? Submit your suggestion here: https://forms.gle/y7vQQ6WHoNgKeJmh8 Thank you for being a part of our little Last Minute Lecture family! Marks' Basic Medical Biochemistry Chapter 4 summary, water acids bases buffers explained, dipolar nature of water hydrogen bonds, osmolality osmotic pressure body fluids, acid base balance biochemistry, Henderson Hasselbalch equation pKa pH, bicarbonate buffer system blood regulation, hemoglobin phosphate protein buffering, diabetic ketoacidosis case study Dianne A., aspirin salicylate poisoning Dennis V., respiratory alkalosis anxiety Percy V., metabolic acidosis lactic acid ketone bodies sulfuric acid, electrolytes Na K Cl HCO3 biochemistry, osmotic diuresis dehydration and intravenous saline, urinary ammonium phosphate acid excretion, gastric hydrochloric acid neutralization, HbA1C diabetes diagnosis and blood pH
