01 water - UNM Biochemist y ducation Depa tment of...

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Unformatted text preview: UNM Biochemist y ducation Depa tment of Biochemist y & Molecula Biology BIOC 423: I tr duct ry Bi chemistry Biologically Important Properties of Water OBJECTIVES • Describe how the molecular structure of water is related to its physical and chemical behaviors (i.e., high boiling point, heat capacity and ability to dissolve ionic solutes) • Describe the following non-covalent bonding interactions Hydrogen bonding Electrostatic interactions Van der Waal’s forces Hydrophobic interactions • Describe the properties of water that make it unique for biological reactions • Define pH, pOH, pKa, conjugate base and conjugate acid • Be able to interconvert hydrogen ion concentration [H + ] and pH • Be able to use the Henderson-Hasselbach equation to solve for any of its terms • Describe the concept of buffering capacity and the role buffers play in living cells. • Be able to sketch a titration curve for any polyprotic acid • Define pI and be able to estimate the pI for any polyprotic acid or tripeptide. OUTLINE I. Constraints on chemical reactions in living systems A. Colligative properties of water Boiling point Freezing point Vapor pressure Osmotic pressure B. Ionization of water (pH, pKw) II. Solvent Properties of Water and Water Structure A. Hydrophilic Solutes B. Salt and polyelectrolytes C. Hydrophobic molecules III. Noncovalent Binding A. Hydrogen bonds B. Electrostatic interactions C. Van derWaals forces D. Hydrophobic interactions IV. Acids, Bases and Titration Curves LECTURE Constraints on chemical reactions in living systems The physical and chemical properties of water make it the optimal solvent for biological reactions. The important biologically characteristics of water are found in water’s colligative and thermal properties as well as the ability of water to ionize. Colligative Properties of water Colligative properties refer to physical characteristics of solvents. These characteristics include vapor pressure, boiling point, melting point and osmotic pressure. The term colligative means combined, connected or “tied together”. Variations in these four properties of water are all tied to the amount of solute dissolved in the water. The fact that solute changes colligative properties (eg., raises boiling point or increases osmotic pressure) is an indication that there is a chemical interaction between water (solvent) and the solute. Biological molecules are for the most part water soluble tied together with the properties of water that make up approximately 70% of the normal tissue. The connection between biological solutes and water solvent (through their colligative properties) gives rise to some very important biochemistry. Because of these forces water will move from high concentration to low concentration in order to come to equilibrium. This movement of water is called osmosis and it is a major force both inside of cells and between cells and the environment. The following three terms are routinely used to compare osmotic pressures of different solutions. terms are routinely used to compare osmotic pressures of different solutions....
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01 water - UNM Biochemist y ducation Depa tment of...

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