University Of The Northern Philippines Biochemistry LC 2B Water And Acid-Base Equilibria PDF

weak enough to allow movement of water and solutes COURSE OUTLINE THERMAL REGULATION I. WATER T...

weak enough to allow movement of water and solutes COURSE OUTLINE THERMAL REGULATION I. WATER The structure of water allows it to resist A. Chemical structure temperature changes B. Properties C. Osmosis Increase heat of fusion: a large drop of D. Dissociation temperature is needed to convert liquid II. ACIDS AND BASES water into solid state A. Definition Increase thermal conductivity: facilitates B. pH and pOH dissipation of heat easily C. Strengths of Acid and Base III. BUFFERS Increase heat capacity and heat of A. Henderson-Hasselbalch evaporation equation IV. REFERENCES WATER AND ACID - BASE EQUILIBRIA I. WATER Predominant chemical component of a living organism Forms an essential part of body cell and body fluids The matrix of many living reactions “Universal solvent” Medium in intracellular and extracellular processes Transport system Important in maintain homeostasis Figure 1. Distribution of body water in average male and female A. CHEMICAL STRUCTURE Total amount of body water + Consists of 2 atoms of 𝐻 and 1 atom of Total amount of body water is 45-80% 2− Water content is dependent on 𝑂 o Body weight Its dipolar nature (both with partial + and – o Age ends) allows it to form hydrogen bonds o Sex which is responsible for its solvent property o Amount of fat Can act as H+ donor and H+ acceptor The younger the patient, the higher the simultaneously water content Has 2 unshared electron pairs that form an Obese persons have less water content electron-densed cloud Females have less water content because A bent molecule with a bond angle of ° they have higher fat content. 104. 3 WATER BALANCE B. PROPERTIES Liquid at room temperature Intake per day Output per day Has a high surface tension Water in food 1250 mL Urine 1500 mL Cohesion: attraction between particles of Oxidation of food 300 mL Skin 500 mL same substance (e.g. surface tension Drinking water 1200 mL Lungs 700 mL which enables insect to walk in water) Feces 50 mL Adhesion: attraction between two different 2750 mL 2750 mL Table 1. Average Fluid Balance Values for Humans. substances High conductivity High latent heat of evaporation WATER AS A SOLVENT Dissolution (because 𝐻2O forms bonds and electrostatic interactions) Although hydrogen bonds are strong enough to dissolve polar molecules in water and to separate charges, they are PREPARED BY: BATCH 2028 1D BIOCHEMISTRY LC 2B: WATER AND ACID-BASE, EQUILIBRIA DR. ESPIRITU, A. DATE: 08/14/2024 Table 2.0. Distribution of Electrolytes REGULATION OF OSMOLALITY Osmolality is regulated by changing the Figure 2. Daily Fluid Loss and Gain. total body water and not by changing body solutes FACTORS THAT AFFECT WATER INTAKE Measurement of osmolality in one o Climate compartment will reflect the osmolality in o Activity all compartments o Diet The serum sodium concentration, being a o State of health measure of body osmolality, is used to diagnose disorders of water balance C. OSMOSIS Osmotic pressure D. DISSOCIATION OF WATER Water distribution is dependent on solute Dissociation of water forms H+ and concentration in the body OH- at 0.0000001M or 10 −7 mol/L It is proportional to the total concentration of all dissolved molecules ▪ pH of water= -log[𝐻 +] = 7 ▪ pOH of water= 7 Osmolality and Osmolarity o A measure of osmotic pressure Acts as partly acid and base o A total concentration of dissolved Dissociation constant particles in a solution o Keq: [𝐻 +][𝑂𝐻 −]/ 𝐻2𝑂 [ ] o Osmolarity: number of particles of o Kw=[𝐻 +][𝑂𝐻 −]= 1×10 −14 solute per liter of solution −14 o Osmolality: number of particles of ▪ [ pKa= -log 1×10 ] = 14 solute per kilogram of solvent The higher the osmolarity, the higher the solute II. ACIDS AND BASES content A. Acid-Base Definition Arrhenius o Acids are substances that increase the concentration of hydronium ions when added to solutions, and base increases the concentration of hydroxide ions. Bronsted-Lowry o Bronsted-Lowry acid is a substance that donates a proton (hydrogen ion), and a Bronsted-Lowry base is a substance that accepts a proton PREPARED BY: BATCH 2028 1D 2 BIOCHEMISTRY LC 2B: WATER AND ACID-BASE, EQUILIBRIA DR. ESPIRITU, A. DATE: 08/14/2024 Lewis III. BUFFERS o Lewis acid is a substance that Certain solutions can resist drastic changes in accepts an electron pair and a pH when small quantities of acids and base Lewis base is a substance that are added to them donates an unshared electron pair Why? If you add an acid, the acid will just react with the conjugate base, so the drastic change will be B. pH and pOH lessened, same is through with adding base, it will Because of the enormous range in the be neutralized with the weak acid concentrations of hydronium and Mixtures of a weak acid and a salt containing its hydroxide ions, we usually use a conjugate base or a weak base and a salt logarithmic scale to express these containing its conjugate acid. concentrations Buffers maintain homeostasis in the body. A. HENDERSON-HASSELBALCH EQUATION the pH of the buffer solution is computed through the Henderson-Hasselbalch equation C. STRENGTHS OF ACIDS AND BASES Weakness and strength of acid depends on the degree of dissociation into H+ ion and a base A strong acid/base is one that completely dissociates Equilibrium Constant for the Dissociation of a Weak Acid The tendency of an acid to dissociate and donate H+ ion to a solution is Ka o Ka= [𝐻 +][𝐴 −]/[𝐻𝐴] o pKa= -log10 Ka Reference: 1. Dr. A. Espiritu (2024). Lecture and Powerpoint Application of weak acids and bases in Presentation. Pharmacology ▪ E.g. Protonated weak base (charged) is more water soluble (hydrophilic), unprotonated weak base on the other hand is uncharged so it is more lipid-soluble (hydrophobic). The unprotonated or protonated form dictates the solubility of the drug and if the drug administered will be easily absorbed by the body. Weak Acids and Bases PREPARED BY: BATCH 2028 1D 3