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of Chemistry Life: Atoms Atom: The basic unit of matter contains electrons(-), protons(+), neutrons(no charge) number of protons and electrons is same and unique for each element H = 1 proton, C = 6 protons, O = 8 protons. This is also the atomic number. Ions Some atoms lose or gain electrons, become charged ions Examples: Na Na+; Cl ClElements of Life Element = substance makes up of only one kind of atom 92 naturally occurring elements "abundance on earth's crust is not mirrored in living tissue" - Some of earth's major elements are not found in cells (ex: Aluminum) - Some major elements in cells are not abundant on earth's crush (Carbon) About 25 elements found in cells Can be identified as Macro and Micro elements Macro-elements: (Chris HOPKINS CaFe Mighty good) these are the elements that are needed and found in abundance in living things Photosynthesis: 6H2O+6CO2 > C6H12O6... Respiration: ... Micro-elements calcium for bone silicon for glassy shell in certain protests potassium and Sodium for nerve conduction in animals Water Polarity Water is a polar molecule It is held together by H-Bonds, which is a type of polar covalent bond. Polar bond refers to the fact that since oxygen is larger (holds more electrons), it pulls more strongly in the bond than hydrogen Think of polarity as in magnets. If each water molecule was a magnet, the opposite poles would stick to each other Water is fundamentally important to study because life as we know it revolves around the characteristics of water: Any volume of water has many hydrogen bonds. This characteristic gives water some unique features. 1. Cohesiveness: The polar covalent bonds between water molecules make them "sticky". It's ahrd to break the surface of water for this reason. 2. Specific Heat: It takes a lot of heat to raise the temperature of water, so it is a very stable substance. Water has a high Specific Heat. (resists change in temperature) 3. Heat of Vaporization: Water needs a lot of heat energy before it will vaporize (form a gas). It has a high heat of vaporization. 4. Heat of Fusion: Water also has a high Heat of fusion. That is, it resists change from a liquid to solid state. When you cool water, it is most dense just before it freezes. When is freezes, the molecules are actually farther apart then just before they became solid. Water is most dense at 4 degrees C 5. Solvent: The ability for other chemicals to dissolve a in water-based solution is very good, due to the polarity of water molecules Acids, Bases, and pH Water ionizes very slightly. H2O = H+ & OHConcentration of pure water is only 10-7 M/liter pH: a way of expressing concentration of familiar numbers. Typically defined as the negative log of H+ concentration. For pure water, pH = 7, since conc. is 10-7 M/liter Acid = any substance that dissociates (ionizes) to produce H+ ions Base = any substance that can accept H+ ions When pure water produces H+ it always produces equal # of HO- ions pH scale 0-14: <7 acid, >7 base, =7 neutral Variation by 1 pH unit is 10x difference in H+ concentration Importance of pH: cell interiors are typically around pH 7 (7.4 in humans) Variation of pH of 1 pH unit is lethal; changes proteins (more on this later), causes death. How do organisms regulate pH? Buffers Buffers are mixtures of acid and corresponding ase, substances that only ionize partially, can "soak up" excess H+ ions Metabolic reactions are dependent on the proper pH. Your body uses buffers (in reponse to changes in cellular pH) to keep the balance. Remember that buffers are used to maintain a certain pH. By definition, buffers help solutions resist change in pH. Example: H2CO3...HCO3- (bicarbonate ion) + H+ HCO3-...CO3= + H+ If H+ is added to solution, gets soaked up by forming more HCO3-, more H2CO3 (Blood plasma 7.4) Saliva -> neutralizing acid in the mouth based mainly on phosphate and carbonic acid Semen -> ph 7.7 maintained by Prostate and Cowper's glands, released base to help buffer the acidity of the urethra, vagina, and uterus Facts Most of our water planet is covered in salt water, covering about 71% of the earth's surface The biotic world is also made up mostly of water, 60% of three's weight is water, in animals including humans the figure is about 50-65% water In terms o f human use, only a small fraction is available for our use. Oceans contain 97% by volume, which is too salty for drinking, irrigation or industrial use. The 3% of earth's total water is considered fresh water. About 2.997% of this fresh water is trapped in polar ice caps and deep within earth surface which is too costly to extract. Thus only .003% of earths' total available water by volume is available for human use. If the worlds water was contained in 100 liters or 26 gallons, then readily available to us would amount to 1/2 teaspoon.

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