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Water
- -principle solvent if living cells, plays a major role in determining the properties of macromolecules
- -significantly higher boiling and freezing temperatures
- -higher heat of vaporization
- -intramolecular attraction/ 2 electric dipoles
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Polar bonds
bonds with a difference in electronegatively giving rise to partial positive and partial negative charges
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Hydrogen Bond
electrostatic attraction between the oxygen atom of one molecule and the hydrogen of another
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Hydrogen Acceptor
usually oxygen and nitrogen, an electronegative atom
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Hydrogen Donor
hydrogen atom covalently bonded to another electronegative atom
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Hydrocarbons
compounds that contain only carbon and hydrogen, which are nonpolar and are typically not soluble in water
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Hydrophobic Effect
the driving force for the formation of biological lipid membranes where hydrophobic molecules consequently cluster, releasing water from constraint
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Amphipathic Compounds
molecule containing both polar (hydrophilic) and nonpolar (hydrophobic) portions; example: fatty acid
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Micelles
structures formed from an amphipathic molecule in the presence of water; the polar head groups are in contact with the aqueous environment and the nonpolar tails are sequestered from the water
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Acid
proton (hydrogen ion) donor
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Base
proton (hydrogen ion) acceptor
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Acid dissociation constant
Ka value, is a measure of the amount of hydrogen ion released when a given amount of acid is dissolved in water (the strength of the acid); the larger the value, the stronger the acid
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Ion product constant for water
Kw, where the concentration of water has been included in its value
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pKa
more convenient numerical measure of acid strength, the smaller its value, the stronger the acid
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Titration
experiment in which measured amounts of base are added to a measured amount of acid
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Equivalence Point
the point of titration at which the acid is exactly neutralized
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Inflection Point
reached in the titration curve when the pH equals the pKa of acetic acid
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Monoprotic Acids
release one hydrogen ion and have a sking Ka and pKa value
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Diprotic Acids
release two hydrogen ions and have two Ka and pKa values
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Polyprotic Acids
release more than two hydrogen ions, and can have several Ka and pKa values
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When the pH of a solution is less than the pKa of an acid, the ________ form predominates
protonated
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When the pH of a solution is greater than the pKa of an acid, the _________ form predominates
deprotonated
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Buffer solution
resists change in pH when small or moderate amounts of a strong acid or strong base are added
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What are the two main buffering systems in living organism?
1. H2PO4-/ HPO42- : cells
2. H2CO3/ HCO3- : blood
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