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CHAPTER 3 WATER & THE FITNESS OF THE ENVIRONMENT. “Life began in water and it has been inextricably tied to water ever since.”. BIOCHEMISTRY IS WET CHEMISTRY ALL METABOLISM OCCURS IN WATER. Water & The Fitness Of The Environment.
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CHAPTER 3WATER & THE FITNESS OF THE ENVIRONMENT “Life began in water and it has been inextricably tied to water ever since.”
BIOCHEMISTRY IS WET CHEMISTRY ALL METABOLISM OCCURS IN WATER
Water & The Fitness Of The Environment A classic book written by LAWRENCE HENDERSON discusses how earth is the only planet in the solar system on which water naturally occurs in all three states…making life as we know it possible.
FITNESS OF THE ENVIRONMENT • 3/4 of earth covered with water • unicellular organisms are completely surrounded by water • most cells contain 70-99% water • H2O is the only element to occur in all 3 states within the range of earth temperatures.
WATER • INTRAMOLECULAR BONDING • Polar covalent bonds • between O and H’s • INTERMOLECULAR INTERACTIONS • Hydrogen bonds • WEAK BOND ENERGY • 4-5 kcal/mol • TRANSIENT - • made and broken every .00000000001 seconds
Many properties of water are the result of H-bonding • Cohesion & surface tension • High specific heat • Evaporative cooling • Expansion during freezing • ice floats
VERSATILE SOLVENT SOLUTION - homogenous mixture SOLVENT - dissolving substance SOLUTE - substance dissolved Do you know what determines solubility?
HYDROPHILIC • water loving molecules have polarity or charge • interact freely w/ h2o soluble • includes ions, sugars, proteins & nucleic acids
HYDROPHOBIC Hydrophobic molecules are nonpolar, nonionic molecules & insoluble in water e.g. lipids, plastics, rain slickers, gases, hydrocarbons
Hydrophobic interactions are essential in the formation of membranes
HYDROPHOBIC INTERACTIONS Soaps and Detergents • Organic Salt + fatty acids • Form a film at the surface • Form micelles under the surface
Solute Concentration in Aqueous Solutions pH & molarity
Unnumbered Figure (page 47) Chemical reaction: hydrogen bond shift
Cells are extremely sensitive to changes in pH To understand biochemistry we needto know a few things about Acids, Bases and pH
ACID • Increases the relative [H+] of in aq. solution. • also removes OH- via association • Acids are proton donors e.g. HCl, H2SO4, H2PO4
Figure 2.0 Bombardier beetle Formic acid Ouch!
BASE • reduce the relative [H+] of a solution. • Or may increase [OH-] • Bases are proton acceptors • reduce[H+] indirectly • E.G. NaOH NH3 HCO3-
DISSOCIATION OF WATER MOLECULES in distilled water the number of H+ and OH-ions in soln. at any given time is a constant IONIZATION CONSTANT OF WATER =10-7
Unnumbered Figure (page 47) Chemical reaction: hydrogen bond shift This is what water does - continuously binding and dissociating
pH simplified measure of the hydrogen ions in solution pH = -log of [H+]
pH • logarithm (base 10) • 1 pH unit = 10 fold change in H+ conc. • inverse relationship between pH/H+ • > pH < [H+]
pH test question How much greater is the [H+] in a solution with pH 2 than a solution with pH 6? Answer: 104 or 10,000x
IMPORTANCE OF pH • pH is vital to the shape/function of proteins • especially enzymes that control metabolism • alterations in pH disrupt H-bonding and change the shape of protein molecules • BIOLOGICAL pH 6-8 (safe range)
BUFFERS • help maintain pH • weak acid + weak base • reservoir for H+ (think sponge) The carbonic acid buffering system helps to maintain the pH of the blood
Acid Rain • Acid precipitation threatens the fitness of the environment • Major source - combustion of fossil fuels by industry & autos. • pH < than 5.6 • as low as 1.5 in West Virginia • “The Challenge of Acid Rain” Scientific American, August, 1988.
