Pre-BIO 320 Notes - TheChemicalBasisofLife CovalentBonds I)

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The Chemical Basis of Life 02:21 Covalent Bonds   I) Molecular atoms are joined together by covalent bonds in which e- pairs are  shared b/w atoms A) Formation governed by the principle that atoms are most stable with a full  outer e- shell. 1) The # of bonds formed is determined by the # of e- needed to fill outer  shell 2) Bond formation accompanied by energy release B) Atoms can be joined by bonds in which >1 pair of e- are shared – if 2 pairs  shared>double bond (O 2 ); if 3 pairs shared>triple bond (N 2 ) C) Type of bond can determine molecular shape – atoms joined by single bond  II) Polar and non-polar molecules A) H 2 0 – O-H bonds in water are polarized (one atom [O] partially -; the other [H]  partially +); it is a polar molecule – such molecules have an asymmetric  charge distribution. B) Biologically important polar molecules have one or more electronegative  atoms – usually O, N, S and/or P H) are non-polar D) Presence of strongly polarized bonds is important in determining molecular  reactivity 1) 2) Molecules w/ electronegative atoms tend to be more reactive 3) Many interesting biological molecules (proteins, phospholipids) have both 
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This note was uploaded on 12/30/2009 for the course CH 45915 taught by Professor Laude during the Spring '09 term at University of Texas at Austin.

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Pre-BIO 320 Notes - TheChemicalBasisofLife CovalentBonds I)

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