“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.

Figure 3.0 Earth

FITNESS OF THE ENVIRONMENT 3/4 of earth covered with water unicellular organisms are completely surrounded by water most cells contain 70-99% water H 2 O 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 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/ h 2 o soluble includes ions, sugars, proteins & nucleic acids

Figure 3.7 A crystal of table salt dissolving in water

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

pH & molarity

Unnumbered Figure (page 47) Chemical reaction: hydrogen bond shift

Figure 3.9 The pH of some aqueous solutions

Cells are extremely sensitive to changes in pH To understand biochemistry we need to 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, H 2 SO 4, H 2 PO 4

Figure 2.0 Bombardier beetle Formic acid Ouch!

BASE reduce reduce the relative [H + ] of a solution. Or may increase [OH - ] Bases are proton acceptors Bases are proton acceptors reduce [H + ] indirectly E.G. NaOH NH 3 HCO 3 -

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: 10 4 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.

Figure 3.10x1 Pulp mill

Figure 3.10x2 Acid rain damage to statuary, 1908 & 1968

Figure 3.10 The effects of acid precipitation on a forest