Module 1 Part 1.docx

Bond resulting in planar geometry typically occurs in

Info icon This preview shows pages 4–6. Sign up to view the full content.

bond, resulting in planar geometry) Typically occurs in molecules that undergo resonance (i.e. a phenomenon where molecules that contain single and double bonds adjacent to each other can exist as an average of multiple structures) o e.g. the molecular structure around the peptide bond (i.e. as a result of resonance, the chemical groups that make up the peptide bond must be located in the same plane due to the partial double-bond character of the carbonyl and amino bonds that restricts rotation about these positions) o e.g. resonance exists in the bases and the phosphate group of the phosphodiester bond, giving the phosphodiester bond a tetrahedral geometry The negative charge on the phosphate group can shift between the two oxygen atoms that are not bound to sugars in the backbone The bases themselves are conjugated ring systems (i.e. they have alternating double and single bonds, giving rise to shared electrons around the ring(s)); the accuracy of base pairing (i.e. A and T; C and G) results from the dominance of particular resonance structures of the bases Resonance hybrid: a molecule that exists in an average of two possible forms Electric dipole moment: combination of separated positive and negative charges Polar and nonpolar regions can exist within the same molecule; the outer surfaces of proteins that function in the aqueous environment tend to be polar (thereby favouring interactions with polar water molecules) and proteins that function in the nonpolar environment of cellular membranes tend to have nonpolar surfaces (thus fostering contacts with the nonpolar fatty acid chains of the membrane).
Image of page 4

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

Ionic interactions can occur between pairs of oppositely charged amino acid side chains; the amino acids with side chains that most often form salt bridges are arginine, lysine, aspartic acid, and glutamic acid . Salt bridge: a link between electrically charged acidic and basic groups, especially on different parts of a large molecule such as a protein (e.g. negative charges on the oxygen atoms in the glutamic acid side chain attract the positive charges on the nitrogen atoms in the arginine side chain, forming a salt bridge) o Involves a combination of two weak interactions: hydrogen bonding and electrostatic interactions Chemical Properties: Weak Chemical Bonds Three kinds of weak chemical interactions are important in biological systems: 1 van der Waals forces o Non-specific contacts between atoms; as two atoms get closer, induced fluctuating charges between them cause a weak, nonspecific attractive interaction that heavily depends on the distance between the interacting atoms o As the distance decreases below a certain point, a more powerful van der Waals repulsive force is caused by overlap of the atoms' outer electron shells o van der Waals radius: distance at which attractive and repulsive forces are balanced; characteristic for each atom o For atoms to interact effectively using van der Waals forces, the intermolecular fit
Image of page 5
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.
  • Winter '13
  • DNA

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern