BIOL FOR SCI MAJ I
BIOL FOR SCI MAJ I BIOL 1201
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This 7 page Class Notes was uploaded by Charles Kohler on Tuesday October 13, 2015. The Class Notes belongs to BIOL 1201 at Louisiana State University taught by F. Sheldon in Fall. Since its upload, it has received 10 views. For similar materials see /class/222807/biol-1201-louisiana-state-university in Biological Sciences at Louisiana State University.
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Date Created: 10/13/15
The Chemical Context of Life 0 Matter consists of chemical elements in pure form and in combinations called compounds 0 Elements and compounds I Elements a substance that cannot be broken down to other substance by chemical reactions 0 92 elements I compounds a substance consisting of two or more different elements combined in a fixed ratio 0 Ex Sodium Chloride NaCl 11 ratio I Molecule Two or more atoms held together by a covalent bond 0 Elements of Life I 2025 of elements are essential elements that organisms need to live a healthy life and reproduce 0 this varies from each organism I Oxygen Nitrogen Carbon and Hydrogen make up 96 of living matter 0 An Element s properties depends on the structure ofits atoms 0 Atom the smallest unit of matter that still retains the properties of an element 0 Subatomic particles I Protons positive charge I Neutrons neutral Electrons negative Nucleus protons neutrons o This is also known as the mass number I Atomic number number ofprotons I Number ofneutrons mass numberatomic number 0 Isotopes all atoms have same number of protons but some have different neutrons a isotope is a different atomic form of the same element I Radioactive isotope one in which the nucleus decays spontaneously giving offparticles and energy 0 Decay leads to a change in the number ofprotons it transforms the atom to an atom of a different element 0 The energy levels of electrons I Energy is defined as the capacity to cause change for instance by doing work 0 Further away form the nucleus more energy absorbed I Potential energy is the energy that matter possesses because ofits location or structure I Electron shell 0 1st shell lowest potentional energy 0 when an electron loses energy it falls back closer to the nucleus 0 electron distribution and chemical properties I look into powerpoint ofpicture I Valence electrons the electrons in outer electrons I Valence shell outermost electron shell I An atom with a completed valence shell is unreactive meaning it wont interact readily with other atoms 0 Covalent bonds sharing of a pair ofvalence electrons by two atoms I Single bonds a pair of shared electrons 0 Ex HH I Double bonds sharing two pairs ofvalence electrons 0 Ex 00 I Electronegativity 9 the attraction of a particular atom for the electrons ofa covalent bond I Nonpolar covalent bonds in a covalent bond between two atoms of the same element the electrons are shared equally because the two atoms have the same electronegativity the tugofwar is at a standoff I Polar covalent bonds when one atom is bonded to a more electronegative atom the electrons of the bond are not shared equally o Ionic bonds I Is an attraction between anions39 and cations o Cations positive charged 0 Anions negative charged I Ionic compounds Are often called salts which may form crystals 0 Weak chemical bonds I Hydrogen bonds Forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom I Van der Waals interactions 0 Occur when transiently positive and negative regions of molecules attract each other 0 They reinforce large molecules 0 Help molecules adhere to one another 0 Chemical reactions make and break chemical bonds 0 Chemical reaction ls the making and breaking of chemical bonds I Leads to changes in the composition of matter I Convert reactants to products Water and Life Life evolved amp stayed in water for 3 billion years out ofwater for 400 million years 70 of earth39s surface is water Cells are about 7095 made up ofwater Polar covalent bonds in water molecules result in hydrogen bonding 0 Polar Covalent Bonds oxygen is more electronegative than hydrogen so the electrons of the covalent bond spend more time closer to oxygen than to hydrogen Polar molecule this is the unequal sharing of electrons and water s Vlike shape I Overall charge is unevenly distributed 0 O has a negative charge 0 H has a positive charge Properties of water come about because the slightly attractions between the opposite charged atoms 0 Hydrogen bond is constantly moving around and reforming 0 Four and of water contribute to earth s suitability for life 0 Cohesion ofWater Molecules I Molecules stay close together because of hydrogen bonds Cohesion hydrogen bonds hold the substance together Adhesion clinging of one substance to another this is how it happens throughout this process v 0 When water clings to the cells wall by hydrogen bonds helps counter the downward pull of gravity Surface tension this is the measure of how hard it is the break the surface of liquid 0 Water has a greater surface tension than other 0 EX When you over fill a cup and it is o Moderation of temperature by water I Heat and temperature 0 Kinetic energy anything that moves 0 Atoms and molecules have kinetic energy 0 lleat form of energy 0 Depending on the body of matter the amount of heat is the measure of the matters total kinetic energy 0 Temperature the measure of heat intensity that represents the average kinetic energy of the molecule regardless to volume 0 EX When water is boiling the avg speed of the molecule increases 0 Calorie the amound of heat it takes to raide the temperature of 1 g of water by 1 C O O o It basically is the amount ofheat that 1g of water releases when it cools by 1C I Water s high specific heat 0 Specific heat the amount ofheat that must be absorbed or lost for 1g of that substance to change its temperature by 1C 0 Water 1 calgC 0 Because of specifc heat water will change temp less when it absorbs or loses a given amount of heat 0 Also can be seen as I Evaporating cooling 0 Heat ofvaporization the quality of heat liquid must absorb for lg ofit to be converted from the liquid to the gaseous 0 To evaporate heat 1g ofwater at 25C about 580cal of heat is needed 0 Evaporative cooling s the quothottestquot molecule with the greatest kinetic energy are the most likely to leave as gas 0 This contributes to the temp in lakes and ponds o Floating ofice on liquid water I When temp drops molecules slow down to break hydrogen bonds 0 At 0C the molecules become locked into a crystalline lattice o The hydrogen bonds keep the molecules at quotarms length far enough apart to make ice about 10 less dense 10 fewer molecules for the same volume than liquid water at 4C 0 When a big body of water is cooled the ice is formed to insulate the liquid water below I This allows life to live under the water 0 Water the Solvent oflife I Solution a liquid that is completely homogeneous miXture of two or more substance Solvent dissolving agent ofa solution 0 EX Water Solute substance that dissolving happens in Aqueous solution the one in which water is the solvent Hydration shell the sphere of water molecules around each dissolved ion Compound doesn t need to be ionic to dissolve in water 0 EX Sugar is nonionic polar molecule and it is dissolved in water o It dissolves because when the water surrounds the solvent molecule such as sugar they form hydrogen bonds with them and this breaks the solvent down which eventually makes it dissolve 0 Figure 38 below Insert here 0 Hydrophilic and hydrophobic substances I Hydrophilic a molecule or other molecular entity that is attracted to and tends to be dissolved by water 0 EX Cotton consist of a giant molecule of cellouse it has regions of positive and negative charged partial that can form hydrogen bonds with water 0 It dries your body but doesn t dissolve in the washer machine I Hydrophobic the do not have an affinity to water it is nonionic and nonpolar it cannot form hydrogen bonds it repels water 0 EX Veggie oil does not mix stably with water based substances such as vinegar 0 This is for likeoils in the cell membrane because DUH you don t want you cell membrane to dissolve that would be bad 0 Solute concentration in Aqueous solutions I Most chemical reactions happens in water 0 You can only know the caluations if you the number of atoms and the molecules involved and know the concentration of the solutes in an aquesous solution 0 You nd that out knowing the molecules in a volume of solutions If you know the mass of each atom in the given molecule we can calculate the molecular mass the sum of the masses of all the atoms in a molecule 0 Measured in moles represents an exact number of objects 602X10A239 Avogadro number Molarity he number of moles of solute per liter of solution is the unit of concentration most often used by biologist for aqueous solution 0 Possible evolution of life on other planet with water 0 Acidic basic conditions affect living organisms 0 Hydrogen ion H9 the hydrogen atom leaves its electron behind and this is what is actually left behind a single proton with a charge of 1 0 Hydroxide ions OH9has a charge of l o Hydronium ion H30 lhe proton binds to the other water molecule making that molecule 0 Figure pg 53 0 Double arrows reversible reaction that reaches a state of dynamic equilibrium when water molecules dissociate at the same rate that they are being reformed from H and OH I Equilibrium point great exceeds the concentration of H and OH 0 Pure water only one molecule in every 554 million dissociated the concentration of each ion in pure water is lOA7 M at 25 degrees celeius 0 Concentration of H and OH are equal in pure water but adding certain kinds of solute called acids and bases disrupts this balance 0 Acids and bases 0 Acids a substance that increases the hydrogen ion concentration of a solution 0 Base a substance that reduces the hydrogen ion concentration of a solution I Some bases reduce the H7 concentration directly by accepting hydrogen ions 0 The pH scale 0 The produce of the H and OH concentrations is constant at 10Al4 I HOH10Al4 o bracket indicate molar concentration 0 solution at room temperature 25C H10A7 and OH 10A7 acid adds hydrogen ions to a solution removes Hydroxide ions because of the tendency for H to combine with OH forming water Base increasing OH concentration but also reducing H concentration by the formation of water 0 pH9 the negative logarithm of the hydrogen ion concentration I pHlog H I neutral aqueous solution 0 log 10A7 77 I 7 is pure water 0 the lower the number the more acidic the solution is 0 Ex Battery acid win cola rainwater o The higher the number the more basic it is o EX House bleach o Buffers a substance that minimizes changes in the concentration of H and OH in a solution 0 This happens because ti accepts hydrogen ions from the solution when they are in excess and donating hydrogen ions ot the solution when they have been depleted o Acidi cation A threat to water quality 0 Carbon dioxide is the main product of fossil fuel I 25 ofhuman generated C02 is absorbed by oceans I acid precipitation refers to rain snow or for with pH lower more acidic than 52 o uncontaminated rain is about 56 pH 0 it can damage lakes and streams which affects the land and soil
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