Biochemistry Week 12 PDF

1. Describe Human Buffering Processes That Adjust Blood pH Buffering Systems in the Body: The body's primary buffer systems are bicarbonate-carbonic acid, protein buffers, and phosphate buffers. These systems resist drastic pH changes by neutralizing acids and bases....

1. Describe Human Buffering Processes That Adjust Blood pH Buffering Systems in the Body: The body's primary buffer systems are bicarbonate-carbonic acid, protein buffers, and phosphate buffers. These systems resist drastic pH changes by neutralizing acids and bases. ○ Bicarbonate-Carbonic Acid Buffer: Maintains pH by balancing carbonic acid (H₂CO₃) and bicarbonate ions (HCO₃⁻). Example reaction: CO₂ + H₂O ↔ H₂CO₃ ↔ H⁺ + HCO₃⁻. Excess hydrogen ions (H⁺) are neutralized by HCO₃⁻, forming H₂CO₃, which breaks down into CO₂ and H₂O, easily exhaled. ○ Protein Buffers: Account for two-thirds of blood buffering, especially in cells. Amino acids have carboxyl (-COOH) and amino (-NH₂) groups that either donate or accept H⁺. Hemoglobin, found in red blood cells, buffers H⁺ during CO₂ conversion into bicarbonate. ○ Phosphate Buffer: Plays a significant role in intracellular buffering. Converts strong acids/bases to weaker forms via reactions like HPO₄²⁻ + H⁺ ↔ H₂PO₄⁻. 2. Explain Respiratory and Renal Contributions to Acid-Base Balance Respiratory Regulation: The respiratory system manages blood pH by adjusting CO₂ levels: ○ Increased CO₂ → More H₂CO₃ → Lower pH (acidosis). ○ Decreased CO₂ → Less H₂CO₃ → Higher pH (alkalosis). Respiratory rate adjustments: ○ Hyperventilation reduces CO₂, increasing pH. ○ Hypoventilation retains CO₂, decreasing pH. Chemoreceptors in the brain and peripheral arteries monitor CO₂ and H⁺, signaling the respiratory center for immediate adjustments. Renal Regulation: Kidneys maintain acid-base balance by: ○ Excreting H⁺ into urine and conserving HCO₃⁻ in blood. ○ Generating new bicarbonate ions via tubular processes. Renal compensation is slower but effective over hours to days, as it corrects metabolic pH imbalances: ○ Acidosis: Enhanced H⁺ secretion and HCO₃⁻ conservation. ○ Alkalosis: Reduced H⁺ secretion and HCO₃⁻ conservation. 3. Differentiate Between the Key Characteristics and Compensation Mechanisms of Metabolic and Respiratory Alkalosis and Acidosis Condition Cause Compensation Key Features Mechanism Metabolic Bicarbonate deficiency Respiratory system Low pH, low Acidosis (e.g., diarrhea, increases ventilation (CO₂ HCO₃⁻, low or ketoacidosis) exhalation). normal CO₂. Metabolic Excess bicarbonate (e.g., Respiratory system High pH, high Alkalosis antacid overuse, vomiting) decreases ventilation to HCO₃⁻, high or retain CO₂. normal CO₂. Respiratory CO₂ retention (e.g., Kidneys conserve HCO₃⁻ Low pH, high CO₂, Acidosis hypoventilation, lung and secrete H⁺. high or normal disease) HCO₃⁻. Respiratory Excess CO₂ exhalation Kidneys excrete HCO₃⁻ High pH, low CO₂, Alkalosis (e.g., hyperventilation) and conserve H⁺. low or normal HCO₃⁻. Compensation timelines: Respiratory compensation is faster (minutes). Renal compensation takes hours to days but is more robust. 4. Describe the Constituents of Arterial Blood Gas (ABG) Arterial Blood Gas Analysis: pH: Indicates overall blood acidity or alkalinity (normal range: 7.35–7.45). PaCO₂: Measures partial pressure of CO₂, reflecting respiratory contribution (normal range: 35–45 mmHg). HCO₃⁻: Represents bicarbonate concentration, reflecting metabolic contribution (normal range: 22–26 mEq/L). PaO₂: Measures oxygenation (normal range: 75–100 mmHg). Base Excess/Deficit: Quantifies buffer base reserve or deficit to further diagnose metabolic conditions. Steps in ABG Interpretation: 1. Determine pH: Acidosis (7.45)? 2. Evaluate PaCO₂ and HCO₃⁻ to identify respiratory or metabolic origin. 3. Assess compensation status: ○ Uncompensated: Only one parameter abnormal. ○ Partially compensated: Both parameters abnormal; pH still outside normal.