Biol 1201 Science 04 30 2014 The use of evidence to construct testable explanations and predictions of natural phenomena as well as the knowledge generated through this process Key points about the nature of science Science originates in questions about the natural world Science uses observations and evidence to construct explanations about phenomena and testable hypothesis The more observations and other kinds of evidence Use a variety of techniques to investigate the natural world Make explanations public through presentations and publications Scientists Our typical experience Body temp 37C 1 atm pressure Range of conditions for life Cell body temps From 2C to 132C Range of pressures 1 atm 1100 atm Conditions of the average depth of the ocean 2C 4C 380 atm of pressure No sun light Antarctic fishes Penguins Diving seal Keep warm at similar temps endotherm Can hold their breath for 90 minuets Can dive down to 1500 meters Deep sea fishes Live and have body temps at 2C below the freezing temp of most vertebrates body fluids ecotherm Can dive down to 7000 meters High pressure Piezophiles Barophiles Bacteria Thermophiles Bacteria Halophiles Sharks Tuna fish Thermophiles exist at temps up to 130C grow at 122C Halophilic bacteria live in osmotic equilibrium Live in molar urea in their tissues Urea is a potent denaturant of protein Raise the temp of their muscles above the ambient as much as 15C Great white shark and sword fish are endotherms in contrast to exothermic Gutless tubeworm Thrive at deep sea hydrothermal vents Midwater fish and invertebrates Organisms living in the water column achieving neutral buoyancy despite the high density of themselves Pure substances that cant be broken down into simpler substances Chemistry background Elements 92 natural elements 112th element copernicium Cn 6 others un named Atom smallest unit into which on element can be divided components proton 1charge 1 Dalton mass neutron neutral charge 1 Dalton mass electron 1 charge essentially without mass number of protons in the nucleus number of protons and neutrons in the nucleus atomic number atomic mass electrical charge compound chemical bonds number of electrons number of protons an ion the number of electrons is not equal to the protons a substance that can be broken down to 2 or more elements forces holding atoms together in molecules What determines the number and type of chemical bonds Number Valence Type Electronegativity Electronegativity The tendency of an atom to attract a bonding pair or electrons Measure of the attraction an atom has for electrons Check Moodle in the BIOLOGICAL MOLECULES folder for diagram Chemical bonds Forces holding atoms together in molecules Characterized as strong or weak depending on the energy required to make break the bonds Strong covalent bonds involve sharing of electrons Weak noncovalent bonds Ionic interaction one atom donates an electron to another Hydrogen bonds between partially charged atoms Valence is the number of electrons needed to fill the outer shell of an atom Valence electrons are the electrons contained in the outer shell of an Valence vs Valence electrons atom Moles and molar concentration 1 Mole the mass of a substance equal to its gram molecular weight 1 molar solution a solution containing 1 mole of a substance per 1 liter of solution Covalent Bonds Strong bond sharing of electrons ex H2O Polar covalent bond Unequal sharing of electron s Partial or Partial regions No net charge Hydrogen bonds Weak non covalent Between partial positive and partial negative Water Does it set the upper temp for life forms Probably not Important role in structures and properties of biological molecule Water is a biological molecule Unusual Properties Hydrogen bonding Water behaves as a much larger molecule H O covalent polar 110kCal per mole Angle 104 5 degrees Weak hydrogen bonds 4 5kCal per mole Hydrogen bonding makes water a larger molecule In ice a molecule will interact with exactly 4 other molecules In liquid a molecule will interact with 3 6 molecules and can be broken very easily Small molecules a comparison of properties Water 100C 0C Ammonia 35C 37C Ethanol 78 5C 117 3 C amount of heat to raise 1 gram 1 degree C 1 High heat capacity 1 cal per 1 gram 2 Heat Vaporization amount of heat to vaporize 1 gram of H2O 540 cal per gram 100C 3 Heat of fusion amount of heat removed to freeze 1 gram of water 80 cal gram to get ice formation Freezing Melting point Super Cooling Under Cooling The temp at which the vapor pressure over liquid phase Cooling of liquid below its freezing point without the formation of ice crystals certain temp A meta stable state an equilibrium state which is not very stable at a Embryo crystal seeds the solution when a critical radius is reached Ice forms spontaneously In the absence of heterogeneous nucleators Pure Water Ice Nucleators Proteins Polysaccharides sugars Prevents super cooling and rapid freezing Ice formation Ice nucleators Release heat of Maintain fluid and plant temperature at 0C Water is most dense at 4C Because or the hydrogen bonding This is why lakes freeze from top to bottom If the lakes froze from bottom to top then life could not live High dielectric Good solvent Interacts with other biological molecule Capillary action and surface tension Can ionize Dissociation into acid hydronium ion And base hydroxyl ion pH review acids bases and salts acids bases salts produce H ions produce hydroxide ions produce neither pH log 1 H log H actually activity of the H concentration pH scales log base 10 the difference btw pH 3 and pH4 is a 10 fold diff in the the diff btw pH 3 and pH 5 is a 100 fol diff in the concentration of concentration H pH of 7 is neutral pH below 7 is acidic pH above is basic pOH pOH log 1 OH log OH pH pOH 14 Neutrality H OH log H log oh pH pOH 1000 3 orders of magnitude increasing proton 11 decreases pH substances that maintain a constant pH solute molecules that are dissolved in the solvent buffers solubility solvent What determines solubility Like dissolves like Like in terms of polarity Polar solutes dissolve polar solvents Non polar solutes dissolve in non polar Hydrophilic substance interact with water solvents molecules Except for water all are built on a carbon skeleton Biological molecules Water Lipids Carbohydrates Proteins Nucleic acids Functional groups Hydroxyl alcohols Large molecules constructed from smaller molecules Polymers constructed from monomers Carbonyl aldehydes terminal carbon and
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