Biochemistry Module 3 PDF

BIOCHEMISTRY Module 3 pH “potential of Hydrogen” a measure of the acidity or alkalinity of a solution equal to the common logarithm of the reciprocal of the concentration of hydrogen ions in moles per cubic decimeter of solution. Pure water has a pH of 7, acid solutions have a pH less t...

BIOCHEMISTRY Module 3 pH “potential of Hydrogen” a measure of the acidity or alkalinity of a solution equal to the common logarithm of the reciprocal of the concentration of hydrogen ions in moles per cubic decimeter of solution. Pure water has a pH of 7, acid solutions have a pH less than 7, and alkaline solutions a pH greater than 7. Problem #1 What is the pH of the solution if the [H3O+] concentration is 5.5x10^-4 M? Given: [H3O+]= 5.5x10^-4 M Unknown: pH = ? Equation: pH = -log (H3O+) Substitution: pH = -log (5.5x10^-4) Problem #1 What is the pH of the solution if the [H3O+] concentration is 5.5x10^-4 M? Given: [H3O+]= 5.5x10^-4 M Unknown: pH = ? Equation: pH = -log (H3O+) Substitution: pH = -log (5.5x10^-4) Problem #2 The pOH of the solution is 5.7. Calculate the pH of the solution? Given: pOH = 5.7 Unknown: pH = ? Equation: 14 = pH + pOH pH= 14-pOH Substitution: pH = 14-5.7 Problem #2 The pOH of the solution is 5.7. Calculate the pH of the solution? Given: pOH = 5.7 Unknown: pH = ? Equation: 14 = pH + pOH pH= 14-pOH Substitution: pH = 14-5.7 Problem #3 If the pOH is 4.3. What is the [OH-] concentration? Problem #3 If the pOH is 4.3. What is the [OH-] concentration? Given: pOH= 4.3 Unknown: OH- = ? Equation: [OH-]= antilog (-pOH) Substitution: [OH-]= antilog (-4.3) Problem #4 What is the pOH of the solution if the [H3O+] concentration is 5.2x10-3? Problem #4 What is the pOH of the solution if the [H3O+] concentration is 5.2x10-3? Given: [H3O+] = 5.2X10^-3 Unknown: pOH=? Equation: pH= -log(H3O+) 14 = pH + pOH Substitution: pH= -log(5.2X10^-3) Problem #5 If the ka of an acid is 1.7 x 10-5, calculate the pka and pkb values of the acid? Problem #5 If the ka of an acid is 1.7 x 10-5, calculate the pka and pkb values of the acid? BUFFER A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable. BUFFER A Buffer solution is a solution that contains a weak acid or base that is capable of resisting or minimizing the change in pH upon the addition of a strong acid or base. Buffer solutions can be prepared in the laboratory by mixing a weak acid and its conjugate base or a weak base and its conjugate acid.  The Henderson-Hasselbach equation is helpful in calculating the proportions of weak acid and its conjugate base or weak base and its conjugate acid needed to prepare the buffer. Problem #1 What is the pH of a buffer solution that is 0.5M in formic acid (HCHO2) and 1.0M in sodium formate (NaCHO2)? The pKa for formic acid is 3.74. Problem #1 What is the pH of a buffer solution that is 0.5M in formic acid (HCHO2) and 1.0M in sodium formate (NaCHO2)? The pKa for formic acid is 3.74. Problem #2 What would be the pH of a 100mL solution containing 0.24M formic acid (HCHO2; Ka= 1.8x10-4) and 0.24M sodium formate (NaCHO2) Problem #2 What would be the pH of a 100mL solution containing 0.24M formic acid (HCHO2; Ka= 1.8x10-4) and 0.24M sodium formate (NaCHO2)  Maintaining the pH of cells and tissues is important for maintaining body homeostasis or equilibrium. Blood pH is maintained at 7.35 < pH < 7.45. A slightly acidic pH < 6.95 can lead to coma and death from acidosis, and a slightly basic pH > 7.70 can cause convulsions and muscle spasms from alkalosis. Importance of pH in living cells7 : In animals, for example, the maintenance of blood pH (7.35 < pH < 7.45) is crucial for life. Slightly acidic pH (6.95) →coma and death. Slightly basic pH (7.7) → convulsions and muscle spasms. Dramatic shifts in pH can play a role in controlling cellular activities such as egg division after fertilization and enzymatic activities Consequently, cells must work constantly to maintain an acid-base balance. Acidosis and Alkalosis NORMAL BLOOD pH : 7.35 - 7.45 ACIDOSIS and ALKALOSIS metabolic disturbances in the acid-base balance of the body. conditions in which there is a disturbance in the pH balance (acid-base balance) of the body.  ACIDOSIS condition in which the acidity of body fluids & tissues is abnormally high due to a decrease in normal blood pH - major physiological effect in general: depression of the CNS through depression of synaptic transmission TYPES OF ACIDOSIS: 1. Metabolic Acidosis occurs when there is excessive loss of bases, such as bicarbonate (HCO3 - ) or sodium due to a decrease in blood HCO3 – CAUSES: a. Severe ketosis & Diabetes Mellitus (DKA) b. Eclampsia c. High lipid diet d. Urinuria  2. Respiratory Acidosis (hypoventilation) associated with an increased level of CO2 in the blood, occurring when there is interference with respiratory gas exchange carbon dioxide combines with water to form carbonic acid (H2CO3) carbonic acid can dissociate into hydrogen ions, which will lower the pH of the blood (acidosis) ALKALOSIS condition in which the alkalinity of body fluids and tissues is abnormally high. This arises because of a failure of the mechanisms that usually maintain a balance between alkalis and acids in the arterial blood. associated with loss of acid through vomiting or excessive sodium bicarbonate intake due to an increase in blood pH major physiological effects: over excitability of the CNS through facilitation of synaptic transmission Types of Alkalosis 1. Metabolic Alkalosis is usually associated with excessive loss of potassium and chloride due to an increase in blood HCO3 2. Respiratory Alkalosis produced by hyperventilation (salicylate poisoning or artificial respirator) which lowers the CO2 level of the blood. due to a decrease in blood H2CO3 due to hyperventilation - breathing that is abnormally deep in relation to the amount of physical exercise may lead to respiratory alkalosis which may produce symptoms of muscular weakness or cramp TYPES OF ACIDOSIS TYPES OF ALKALOSIS EXAMPLE #1 Case 1: A 35 year old Hispanic -American female with broken ankle was brought to the emergency room with severe pain. ABGs showed: pH: 7.95 pCO2: 29 pO2: 105 HCO3: 22 Based from the laboratory results of the patient, what is the acid base disturbance? EXAMPLE #1 Case 1: A 35 year old Hispanic -American female with broken ankle was brought to the emergency room with severe pain. ABGs showed: pH: 7.95 pCO2: 29 pO2: 105 HCO3: 22 Based from the laboratory results of the patient, what is the acid base disturbance? Answer: Respiratory Alkalosis pH is high, so alkalosis HCO3 is normal or within normal limits, not metabolic problem pCO2 is low EXAMPLE #2 A 28 year old African-American male was transported to the emergency room due to palpitations. He looked very anxious and breathing heavily. ABGs showed: pH: 7.54 pCO2: 26mmHg HCO3: 23 What is the acid base abnormality? EXAMPLE #2 A 28 year old African-American male was transported to the emergency room due to palpitations. He looked very anxious and breathing heavily. ABGs showed: pH: 7.54 pCO2: 26mmHg HCO3: 23 What is the acid base abnormality? Answer: Respiratory Alkalosis pH is high, so alkalosis HCO3 is normal or within normal limits, so not metabolic problem pCO2 is low EXAMPLE #3 A 71 year old heavy smoker Mexican has chronic obstructive pulmonary disease (COPD). For 2 days, he cough with purulent sputum and fever. The healthcare practitioner suspect exacerbation of COPD. He was drowsy and cyanosed. ABGs showed: pH: 7.2 pCO2: 80 pO2: 50 HCO3: 26 What is the likely acid base abnormality and what is the reason behind cyanosis? EXAMPLE #3 A 71 year old heavy smoker Mexican has chronic obstructive pulmonary disease (COPD). For 2 days, he cough with purulent sputum and fever. The healthcare practitioner suspect exacerbation of COPD. He was drowsy and cyanosed. ABGs showed: pH: 7.2 pCO2: 80 pO2: 50 HCO3: 26 What is the likely acid base abnormality and what is the reason behind cyanosis? Answer: Respiratory Acidosis pH is low, acidosis pCO2 is high HCO3 is normal or within normal limits, so not metabolic problem EXAMPLE #4 A 49 year old hypertensive man from Dagupan City is taking thiazide diuretic. On routine analysis, his ABGs show: pH: 7.50 pCO2: 45 HCO3: 34 What is the acid base abnormality and what is the cause? EXAMPLE #4 A 49 year old hypertensive man from Dagupan City is taking thiazide diuretic. On routine analysis, his ABGs show: pH: 7.50 pCO2: 45 HCO3: 34 What is the acid base abnormality and what is the cause? Answer: Metabolic Alkalosis pH is high, so alkalosis pCO2 is normal or within normal limits, so not respiratory problem HCO3 is high EXAMPLE #5 A 10 year old girl with polyphagia and polyuria since 1 month old. Blood glucose level, serum ketones and urine ketones were high. Patient was dehydrated. ABGs showed: pH: 7.23 pCO2: 35 HCO3: 16 What is the acid base abnormality and what is the cause? EXAMPLE #5 A 10 year old girl with polyphagia and polyuria since 1 month old. Blood glucose level, serum ketones and urine ketones were high. Patient was dehydrated. ABGs showed: pH: 7.23 pCO2: 35 HCO3: 16 What is the acid base abnormality and what is the cause? Answer: Metabolic Acidosis pH is low pCO2 is normal, or within normal limits. HCO3: low, so it is metabolic problem.