This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: BIO 320 - CELL BIOLOGY – Spring 2010 T. O’Halloran & A. De Lozanne Lecture 1 (01/19/10) - The Chemical Basis of Life & Protein Structure Alberts 5th.Ed. – pgs. 45-54; 62-64; 106-111; 125-147; 175-177 I MPORTANT C ONCEPTS YOU S HOULD R EMEMBER FROM YOUR P REVIOUS C OURSES : T HE C HEMICAL B ASIS O F L IFE Covalent Bonds I. Molecular atoms are joined together by covalent bonds in which electron pairs are shared between atoms A. Formation governed by the basic principle that atoms are most stable with a full outer electron shell 1. The number of bonds formed is determined by the number of electrons needed to fill outer shell 2. Bond formation accompanied by energy release B. Atoms can be joined by bonds in which >1 pair of electrons 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 can rotate relative to one another; double & triple bonds cannot II. Polar and non-polar molecules A. Water - O-H bonds in water are polarized (one atom [O] partially negative; the other [H] partially positive); 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) C. Molecules without electronegative atoms & polar bonds (those consisting of C & H) are nonpolar D. Presence of strongly polarized bonds is important in determining molecular reactivity 1. Molecules without electronegative atoms (waxes & fats) are relatively inert 2. Molecules with electronegative atoms tend to be more reactive 3. Many interesting biological molecules (proteins, phospholipids) have both polar & nonpolar regions & behave very differently III. Ionization - some atoms are so strongly electronegative that they can capture electrons from another atom during a chemical reaction A. Sodium (Na; silver colored metal) & chlorine (Cl; toxic gas) - mix them; together form table salt 1. Single electron in Na outer shell migrates to electron-deficient chlorine atom 2. Each atom becomes charged ( ion ): Cl- (anion) and Na + (cation); together form crystal B. Ions like Na + and Cl- are relatively stable because of filled outer shell C. A different electron arrangement in atom produces highly reactive species ( free radical ) Noncovalent Bonds I. Noncovalent bonds govern interactions between molecules or different parts of a large biological 1 BIO 320 - CELL BIOLOGY – Spring 2010 T. O’Halloran & A. De Lozanne molecule; such bonds are typically weaker linkages...
View Full Document
This note was uploaded on 04/12/2010 for the course PSY 339 taught by Professor Neal during the Spring '09 term at University of Texas.
- Spring '09