Biology Notesss

Biology Notesss - 23:43 The number of electrons has to...

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23:43 The number of electrons has to equal the number of protons. What determines the number and type of chemical bonds? Number=valence(the number of electrons needed to fill the outer shell Type=electronegativity Electronegativity: a measure of the tendency of an atom to attract a bonding pair of electrons Measure of the attraction an atom has for electrons *Figure Posted on Moodle in Biological Models Folder* Chemical Bonds: forces holding atoms together in molecules Characterized as strong or weak depending on the energy required to make or break those bonds Strong Bond: covalent bonds involve the sharing of electrons Weak Bond: non-covalent bonds, do not involve the sharing of electrons Ionic interactions: attraction of opposite charges. One atoms donates an electron to another Hydrogen Bond between partial positive and negative charged atoms in a molecule Valence vs. Valence electrons Valence: is the number of electrons needed to fill the outermost shell of an atom Valence Electrons: the number of electrons contained in the outermost electron shell of an atom
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Moles and Molar Concentrations 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 EX. Can you have a 1 molar solution of insulin? 5.727 kg/liter or 5.727 g/cm 3 I kg/L or I g/cm 3 is the density of dry protein Ionic Bonds Weak Bonds Transfer of electrons from one atom to another Covalent Bonds Strong Bonds Sharing of electrons to complete the valence shell Polar Bonds Unequal sharing of electrons Partial ( δ +) and Partial ( δ –) regions No Net Charge Hydrogen Bonds Weak Non Covalent Bonds Between partial positive ( δ +) and partial negative ( δ -) charges Water: Biological Molecule
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70 to 90% of weight of most life forms Sets the lower temperature limit for life Set the upper temperature limit? Probably not Important role in structure and properties of biological molecules Water is a biological molecule The unusual properties of water Result from hydrogen bonding Water behaves as a much larger molecule Bonds Covalent H-O 110 kcal per mole o Weak (hydrogen bond): 4.5 kcal/mol o H bonding effectively makes water a larger molecule In ice a water molecule interacts with exactly 4 other water molecule In liquid water, on average reacts with 3.6 or fewer other molecules (can be made and broken very quickly) Small Molecules- a comparison of properties Water: Boiling point 100C, MP 0C Ammonia: BP 35C, MP -77C Ethanol: BP 78.5C, MP -117.3C
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Unusual Properties of Water 1. High heat capacity: Amount of heat to raise temperature of 1g of water by 1C I cal per g of water 2. High heat of vaporization: Amount of heat to vaporize 1
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This note was uploaded on 08/22/2010 for the course BIOL 1201 taught by Professor Wishtichusen during the Spring '07 term at LSU.

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Biology Notesss - 23:43 The number of electrons has to...

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