ScienceThe use of evidence to construct testable explanations and predictions of natural phenomena as well as the knowledge generated through this processKey points about the nature of scienceScience originates in questions about the natural worldScience uses observations and evidence to construct explanations about phenomena and testable hypothesisThe more observations and other kinds of evidenceScientistsUse a variety of techniques to investigate the natural worldMake explanations public through presentations and publicationsOur “typical” experienceBody temp. 37C1 atm pressureRange of conditions for lifeCell/body temps. From -2C to 132CRange of pressures 1 atm- 1100 atmConditions of the average depth of the ocean2C- 4C380 atm of pressureNo sun lightAntarctic fishesLive (and have body temps) at -2C (below the freezing temp of most vertebrates body fluids) [ecotherm]PenguinsKeep warm at similar temps. [endotherm]Diving sealCan hold their breath for 90 minuetsCan dive down to 1500 metersDeep sea fishesCan dive down to 7000 metersHigh pressurePiezophiles (=Barophiles)BacteriaThermophilesBacteriaThermophiles exist at temps up to 130C (grow at 122C)HalophilesHalophilic bacteria live in osmotic equilibriumSharksLive in ½ molar urea in their tissuesUrea is a potent denaturant of proteinTunaRaise the temp of their muscles above the ambient (as much as 15C)Great white shark and sword fish are endotherms in contrast to exothermic fishGutless tubewormThrive at deep-sea hydrothermal ventsMidwater fish and invertebratesOrganisms living in the water column achieving neutral buoyancy despite the high density of themselvesChemistry backgroundElementsPure substances that cant be broken down into simpler substances92 natural elements112th element copernicium (Cn)6 others un-namedAtomsmallest unit into which on element can be dividedcomponentsproton (+1charge, 1 Dalton mass)neutron (neutral charge, 1 Dalton mass)electron (-1 charge, essentially without mass)atomic numbernumber of protons in the nucleusatomic massnumber of protons and neutrons in the nucleuselectrical chargenumber of electrons = number of protonsan ion, the number of electrons is not equal to the protonscompounda substance that can be broken down to 2 or more elementschemical bondsforces holding atoms together in moleculesWhat determines the number and type of chemical bonds?Number = ValenceType = ElectronegativityElectronegativityThe tendency of an atom to attract a bonding pair or electronsMeasure of the attraction an atom has for electrons** Check Moodle in the BIOLOGICAL MOLECULES folder for diagram**Chemical bondsForces holding atoms together in moleculesCharacterized as strong or weak depending on the energy required to make/break the bondsStrong- covalent bonds involve sharing of electronsWeak- noncovalent bondsIonic interaction- one atom donates an electron to anotherHydrogen bonds between partially charged atomsValence vs. Valence electronsValence is the number of electrons needed to fill the outer shell of an atomValence electrons are the electrons contained in the outer shell of an atomMoles and molar concentration1 Mole = the mass of a substance equal to its gram molecular weight1 molar solution = a solution containing 1 mole of a substance per 1 liter of solutionCovalent BondsStrong bond; sharing of electrons (ex.H2O)Polar covalent bondUnequal sharing of electron(s)Partial + or Partial – regionsNo net chargeHydrogen bondsWeak (non-covalent)Between partial positive and partial negativeWaterDoes it set the upper temp for life forms? Probably notImportant role in structures and properties of biological moleculeWater is a biological moleculeUnusual PropertiesHydrogen bondingWater behaves as a much larger moleculeH-O = covalent polar 110kCal per moleAngle 104.5 degreesWeak hydrogen bonds- 4.5kCal per moleHydrogen bonding makes water a larger moleculeIn ice a molecule will interact with exactly 4 other moleculesIn liquid a molecule will interact with 3.6 molecules and can be broken very easilySmall molecules: a comparison of propertiesWater– 100C 0CAmmonia– 35C -37CEthanol- 78.5C -117.3 C1. High heat capacityamount of heat to raise 1 gram 1 degree C1 cal per 1 gram2. Heat Vaporizationamount of heat to vaporize 1 gram of H2O540 cal per gram @ 100C3. Heat of fusionamount of heat removed to freeze 1 gram of water80 cal/gram to get ice formationFreezing/ Melting pointThe temp at which the vapor pressure over liquid phaseSuper Cooling – Under CoolingCooling of liquid below its freezing point without the formation of ice crystalsA meta stable state= an equilibrium state which is not very stable at a certain tempEmbryo crystal seeds the solution when a critical radius is reachedIce forms spontaneouslyPure WaterIn the absence of heterogeneous nucleatorsIce NucleatorsProteinsPolysaccharides (sugars)Prevents super-cooling and rapid freezingIce formationIce nucleatorsRelease heat of …Maintain fluid and plant temperature at 0CWateris most dense at 4CBecause or the hydrogen bondingThis is why lakes freeze from top to bottomIf the lakes froze from bottom to top then life could not liveHigh dielectricGood solventInteracts with other biological moleculeCapillary action and surface tensionCan ionizeDissociation into acid (hydronium ion)And base (hydroxyl ion)pH-reviewacids,bases,and saltsacidsproduce H+ ionsbasesproduce hydroxide ionssaltsproduce neitherpH=log[1/H+]=-log[H+]actually activity of the H+ concentrationpH scaleslog base 10the difference btw pH 3 and pH4 is a 10-fold diff in the concentrationthe diff btw pH 3 and pH 5 is a 100-fol diff in the concentration of H+pH of 7 is neutralpH below 7 is acidicpH above is basicpOHpOH + log[1/OH-]=-log[OH-]pH + pOH=14Neutrality[H+]=[OH-]–log[H+]=-log [oh-]pH=pOH1000- 3 orders of magnitudeincreasing proton 11-- decreases pHbufferssubstances that maintain a constant pHsolubilitysolute- molecules that are dissolved in the solventsolventWhat determines solubilityLike dissolves likeLike in terms of polarityPolar solutes dissolve polar solventsNon-polar solutes dissolve in non-polar solventsHydrophilic substance interact with water moleculesBiological moleculesExcept for water, all are built on a carbon skeletonWaterCarbohydratesLipidsProteinsNucleic acidsLarge molecules constructed from smaller moleculesPolymers constructed from monomersFunctional groupsHydroxyl- alcoholsCarbonyl- aldehydes (terminal carbon) and ketonesCarboxyl- acid groupAmino- aminesSulfhydryl-
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