110A_02 Chem Basis

110A_02 Chem Basis - BSCI 110A Section 3 Chapter 2 The...

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BSCI 110A Section 3 Chapter 2 The Chemical Basis of Life
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abundance of the elements in the  biosphere and the earth’s crust from Alberts et al ., Molecular Biology of  the Cell
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Arrangement of  electrons in a few  common atoms
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Covalent and noncovalent chemical bonds contribute to the  structure of biomolecules Covalent bonds (50-110 kcal/mol) Covalent bonds are formed when atoms share pairs  of electrons The energy required to cleave is great, making covalent bonds stable under most cellular conditions -C-C- bonds ~85 kcal/mol  Double bonds are formed when atoms share two pairs of electrons.  -C=C- ~150 kcal/mol.  Noncovalent bonds  (<5 kcal/mol) Ionic bonds (~3 kcal/mol): attraction between fully  charged ions Hydrogen bonds (2-5 kcal/mol): partial  charge attraction van der Waals interactions (~0.1 kcal/mol atom): transient  charge Hydrophobic interactions Note : Even through individual noncovalent bonds are weak, their attractive forces are additive. These bonds represent the forces driving inter- molecular interactions in cells.
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Covalent bonds between carbon atoms Versatile building blocks
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Bond configurations for key “biological” elements
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A water molecule (H 2 O) is highly  polar (electrical charge separation) because O is  more  electronegative  than H
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Electronegativities F 3.98 O 3.44 Cl 3.16 N 3.04 S 2.58 C 2.55 H 2.22 P 2.19 Na 0.93 K 0.82 (Pauling scale)
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Each water molecule can hydrogen bond with 4 other water molecules - producing a metastable network These hydrogen bonds constantly
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110A_02 Chem Basis - BSCI 110A Section 3 Chapter 2 The...

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