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lecnotes12 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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_______________________________________________________________________________ ________________________________________________________________________________ Free radicals in biology: a paradox Free radical species damage DNA. Free radicals are essential for life. ive oxygen radicals are a byproduct Free radicals are involved in cell Some enzymes use free radicals to carry out essential reactions in the antioxidant-rich body. For example, a pr Fr si So ca bo otein called ribonucleotide reductase oxidants (such as vitamin a b A, C, and E) reduce (RNR) catalyzes an essential step in DNA synthesis and repair using a free radical species. Free radicals in biology: a paradox Free radical species damage DNA. Free radicals are essential for life. Highly reactive oxygen radicals are a byproduct ee radicals are involved in cell of metabolism and cause DNA damage. gnaling (see NO example on p. 2). Cigarette smoke contains free radicals that can damage DNA in lung cells and lead to cancer. me enzymes use free radicals to rry out essential reactions in the ntioxidant-rich dy. lueberries For example, a protein called ribonucleotide reductase Antioxidants (such as vitamin A, C, and E) reduce (RNR) catalyzes an essential step in DNA synthesis DNA damage in the body by “trapping” radicals. and repair using a free radical species. 5.111 Lecture Summary #12 Readings for today: Section 2.9 (2.10 in 3 rd ed ) , Section 2.10 (2.11 in 3 rd ed ), Section 2.11 (2.12 in 3 rd ed ), Section 2.3 (2.1 in 3 rd ed ), Section 2.12 (2.13 in 3 rd ed ). Read for Lecture #13: Section 3.1 ( 3 rd or 4 th ed ) – The Basic VSEPR Model, Section 3.2 ( 3 rd or 4 th ed ) – Molecules with Lone Pairs on the Central Atom. Topics: I. Breakdown of the octet rule Case 1. Odd number of valence electrons Case 2. Octet deficient molecules Case 3. Valence shell expansion II. Ionic bonds III. Polar covalent bonds and polar molecules I. BREAKDOWN OF THE OCTET RULE Case 1. Odd number of valence electrons For molecules with an odd number of valence electrons, it is not possible for each atom in the molecule to have an octet, since the octet rule works by ____________ e - s.
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This note was uploaded on 03/02/2012 for the course CHEM 5111 taught by Professor Vogel during the Fall '08 term at MIT.

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lecnotes12 - MIT OpenCourseWare http:/ocw.mit.edu 5.111...

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