Water, Acids, Bases, and Buffers PDF

Water, Acids, Bases, and Buffers Kassim Traore, PhD [email protected]  Readings Marks' Basic Medical Biochemistry: A Clinical Approach Sixth, North American Edition Lieberman. ISBN-13 978-1975150143. (available for free in the Duquesne University...

Water, Acids, Bases, and Buffers Kassim Traore, PhD [email protected]  Readings Marks' Basic Medical Biochemistry: A Clinical Approach Sixth, North American Edition Lieberman. ISBN-13 978-1975150143. (available for free in the Duquesne University Electronic Library - through Health Library Medical Education). Recommended Resources Medical Biochemistry 6th edition: John W Baynes, Marek H Dominiczak. ISBN-13: 978-0323834506 (available for free in the Duquesne University Electronic Library - through ClinicalKey). Lippincott Illustrated Reviews: Cell and Molecular Biology, 2e; Chandar. ISBN-13:9781496348500.  Learning Objectives o Discuss properties and the role of water in biological system o Explain the properties of acids, bases and buffers o Discuss the dissociation constant (Ka) of acids, and the pKa of a weak acids o Understand and the use of Henderson-Hasselbach equation to determine pH of a solution and clinical implications. o Explain conditions that may cause changes of blood pH, and the mechanisms of compensation. o Discuss Primary Acid-Base Disorders o Explain the significance of Anion Gap Water by Leila Swenson https://www.google.com/search?q=nature&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjvtaSQ09DjAhXvpVkKHZ- HDUMQ_AUIESgB&biw=1920&bih=969#imgrc=PXPQIb6MdTwn4M: Water Water, is the most critical nutrient for human body. makes up to ~72% of human body weight. level in human body changes with age. Water in the Human Body https://www.usgs.gov/media/images/water-human-body Water in Human Body Most water in human body is contained within cells (intracellular fluid), the rest is in the surrounding our cells (extracellular fluid), with small amount in the blood plasma. Functions of water in human body: helps move nutrients through the digestive tract. acts as a solvent and transport system for minerals and other nutrients in our body. helps maintain the body temperature by dissipating body heat through sweat and respiration. assists in flushing waste mainly through urination. acts as a shock absorber for brain, spinal cord, and fetus. lubricates joints How can water carry all these functions?  Water: Structure and Properties Water carry these functions due to its unique structure and chemical properties 1. Polarity Water is a polar molecule with _ _ positive (+) and negative (-) ends. Dipole structure The polar structure of water make it + an excellent solvent in the biological system. + +  Water: Structure and Properties 2. Solvent for Inorganic salts (ions). o Water molecules can interact with ionic compounds (solutes) and dissolve them. o Water acts as a polar solvent because it can be attracted to either the positive or negative electrical charge on a solute. Example: o NaCl dissolves in water because: – The negative oxygen regions Na+ of water molecules are attracted to + – + sodium cations (Na+). – + N – – a+ + The positive hydrogen regions + Cl of water molecules cling to chloride Cl– – – + – anions (Cl–). + – + – –  Water: Structure and Properties 3. Solvent for Polar organic molecules (Proteins) o Water interacts with polar molecules such as glucose and proteins to form a solution. Example. o Insulin molecule (purple) in an aqueous This oxygen is environment such as blood. attracted to a slight d– positive charge on o Ionic and polar regions on the protein’s the insulin molecule Surface attract water molecules d+ (protein).. Water: Structure and Properties 4. Intermolecular bonds: o Water molecules are linked to each other by hydrogen bonds. o The (+) end of one water molecule attracts the (–) end of another water molecule. https://www.quora.com/Why-do-insects-float- on-water-according-to-the-concept-of-surface- by Leila Swenson https://www.google.com/search?q=nature&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjvtaSQ09DjAhXvpVkKHZ- HDUMQ_AUIESgB&biw=1920&bih=969#imgrc=PXPQIb6MdTwn4M: Acids Bases and Buffers Dissociation of Water Overview Water molecule dissociates to form hydrogen(H+) and hydroxyl (OH−) ions. H2O H+ + OH- In pure water, [H+] = [OH-] = 1 x 10-7 M  The pH of pure Water. pH of a solution is the negative log of its hydrogen ion concentration. pH = -Log[H+] oExample: In pure water, [H+] = 10-7M (mole/L) very small Thus, pH of pure water is calculated as: pH = - Log[H+] pH = - Log(1x10-7) = 7 pH = 7 (neutral) pH = 7 (pure water)  pH of Solution If the pH of a solution is < 7 (acidic) If the pH of a solution is > 7 (basic) If the pH of a solution is = 7 (neutral) Clinical correlate: Normal human blood pH is ~ 7.4, slightly basic may change in certain conditions (acidosis and alkalosis) Acid and Base Overview. *Brönsted-Lowry definition Acid: o is a substance that increases the proton concentration [H+] of a solution, o increases the [H+] ® low pH H+ H+ H + Clinical correlate H+ OHH+ - In patient with uncontrolled Type I Diabetic, excessive H+ H+ production and accumulation of ketone bodies (a weak acid) in the blood causes lower blood pH than normal (acidosis). In intensive exercising muscle, the accumulation of lactic acid (weak acid) causes decrease in the local pH. Base: o is a substance that decreases the proton [H+] of a solution o decreases [H+], increases [OH-] ® high pH o Addition of a base, (E.g.) NaOH, decreases the proton concentration and thus increases the pH of a solution OH- OH- Clinical correlate OH- OH- + In patient, abnormal accumulation of bicarbonate (a base) OH - H OH- OH- in the blood decreases proton concentration and thus causes elevated blood pH than normal (alkalosis)  Acids and Bases Overview. Strong acid and Weak acid o Strong acids (Inorganic acids) dissociate completely and release their hydrogen ions in the solution (Ka > 1; pKa < 1) Example: - Hydrochloric acid (HCl) - Sulfuric (H2SO4), - Nitric acid (HNO3) o Weak acids – (Organic acids) dissociate partially, (Ka < 1; pKa > 1) Example: - Lactic acid - Ketone bodies (acetoacetic acid and β-hydroxybutyric acid) Ka is a dissociation constant of an acid pKa= [- Log Ka] by Leila Swenson https://www.google.com/search?q=nature&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjvtaSQ09DjAhXvpVkKHZ- HDUMQ_AUIESgB&biw=1920&bih=969#imgrc=PXPQIb6MdTwn4M: Henderson – Hasselbach Equation (HH) Overview [HA] [A- ] + [H] [A - ] Henderson-Hasselbach Equation: pH = pK a + log [HA]  Henderson – Hasselbach Equation (HH) Overview Example: Carbonic acid bicarbonate CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+ pKa=6.1 (constant) [ HCO3-] pH = pK a + log [H2CO3] or [HCO3-] pH= 6.1 + log 0.03(PaCO2)] Henderson – Hasselbach Equation (HH) Overview Important Physiological and Clinical Implications [HCO3-] pH= 6.1 + log 0.03(PaCO2)] Blood pH Low High [PaCO2] [HCO3-] Normal human blood pH is = 7.4 Important facts!!! o Human body produces ~ 13 to 22 mole/day of acid through metabolism. Carbonic acid (H2CO3) generated from carbon dioxide (CO2). - This is the major source of acid in the blood Metabolic acids (e.g., lactic acid and ketone bodies), and inorganic acids (e.g., sulfuric acid). o These acids added lot of [H+] and tend to lower the blood pH. o The body must get read of the excess of H+ to maintain the blood pH to normal level of 7.4? Mechanisms of Maintaining Blood pH o Human body relies on a set of mechanisms to maintain the pH of the body fluids in a range compatible with life. o These mechanisms include: the respiratory system to remove carbonic acid through the expiration of CO2, the kidneys to excrete H+ as ammonium ion (NH4+) and other ions. the buffering systems: bicarbonate, phosphate, and hemoglobin buffer systems - Buffer is a system that resist pH changes by adding or accepting proton from a solution (blood) https://simple.wikipedia.org/wiki/Nature#/media/File:Hopetoun_falls.jpg Primary Acid-Base Disorders Acidosis and Alkalosis: Important concepts in Medicine o Acidosis Occurs when the pH of blood and body fluid become lower than normal. There two types: - metabolic acidosis - respiratory acidosis o Alkalosis Occurs when the pH of blood and body fluid become higher than normal. There two types: - metabolic alkalosis - respiratory alkalosis Primary Acidosis I. Metabolic acidosis: o Abnormal lowering of blood pH due to decreasing levels of HCO3- in the blood. [HCO3-] pH= [CO2] o Pathophysiological changes: Metabolic acidosis occurs when excessive quantities of acids (lactic acid and ketone bodies) are produced in the body, or when the kidneys are not able to remove enough acid from the body (due to Chronic renal failure). o Physiological response (a.k.a compensation) Human body responds to metabolic acidosis by stimulating the rate of alveolar respiration. the increased respiratory rate causes in a [CO2 ] in the blood, and thus correct the blood pH back to normal. Primary Acidosis II. Respiratory acidosis: o Abnormal lowering of the blood pH due to accumulation of CO2 which is converted to carbonic acid. [HCO3-] pH= [CO2] o Pathophysiological changes: Respiratory acidosis occurs when the lungs can NOT remove enough of the CO2 produced by the body. The excess of CO2 is converted to carbonic acid which causes the pH of the blood and other bodily fluids to decrease, making them too acidic. o Physiological response /compensation Human body responds to respiratory acidosis by: increasing the level of renal excretion of H+, increasing the level of renal reabsorption HCO3−. Together these changes cause an increased [HCO3− ] in the serum, which then correct the blood pH back to normal Primary Alkalosis I. Metabolic alkalosis: o Abnormally elevated blood pH due to an elevated [HCO3-] caused by excessive loss of acid. o is a very common primary acid–base disorder [HCO3-] pH= [CO2] o Pathophysiological changes: Metabolic alkalosis is caused by significant loss of H+. This causes abnormally elevated serum HCO3- Secondary causes of metabolic alkalosis include: increased HCO3- intake, vomiting and nasogastric tube suction, antacid use. o Physiological response /Compensation: A typical physiological response to metabolic alkalosis is hypoventilation (depressed respiratory rate) which causes compensatory accumulation of CO2 in the blood to correct the pH change Primary Alkalosis II. Respiratory alkalosis: o Abnormally elevated blood pH caused by excessive decrease in the [CO2 ] in the blood. [HCO3-] pH= [CO2] o Pathophysiological changes: Respiratory alkalosis occurs in response to alveolar hyperventilation causing excessive loss of CO2 resulting to abnormally lowering of CO2 levels in the blood (hypocapnia) This causes the pH of blood and other bodily fluids to increase and making them abnormally basic. o Physiological response /compensation Our body responds to respiratory alkalosis by: reducing the level of renal excretion of H+, reducing the level of renal reabsorption HCO3−. Together these changes decrease [HCO3− ] in the serum, which then correct the blood pH back to normal Anion gap o Is an important concept in medicine. o is the calculated difference between the measured cations (positively charged ions) and the measured anions (negatively charged ions) in serum, plasma, or urine. Anion gap = ([Na+] + [K+]) – ([Cl-] + [HCO3-]) Note: Because [K+] are very low, and usually have little effect on the calculated gap, therefore by convenience the following calculation of the anion gap is accepted. Anion gap = [Na+] – [Cl- + HCO3-] Normal Anion gap values The normal Anion gap (reference) ranges is from 10 to 20 mEq/L plasma when [K+] is included. The range is from 8 to 16 mEq/L plasma when [K+] is not including. Note: The term "anion gap" usually implies "serum anion gap", but the urine anion gap is also clinically useful.  Use of the Anion GAP in medicine I. High Anion GAP: o Anion gap is said high if the gap is > normal. o In patient with acidosis, presence of an “High Anion Gap” is an indicator of metabolic acidosis Examples of disorders that cause high Anion gap o Diabetes type1 (ketoacidosis) o Heart failure o Prolonged lack of oxygen (lactic acidosis) THANK YOU!!!! https://images.search.yahoo.com/yhs/search;_ylt=A9FJtrsz0TNbp0YAPOEPxQt.?p=birds&fr =yhs-pty-pty_converter&fr2=piv-web&hspart=pty&hsimp=yhs- pty_converter&type=admk#id=17&iurl=https%3A%2F%2Fweneedfun.com%2Fwp- content%2Fuploads%2F2016%2F06%2Fexotic-birds-1.jpg&action=click