Aqueous Chemistry 2

Question 1

Elements of biochem

Answer 1

• C,N,O,H,P,S constitute 92% of human dry weight
• position in periodic table predicts bonding properties
• common cations (K+, Mg++ inside cell; Na+, Ca++ outside cell)
• anions (Cl-)

Question 2

Geometry of carbon bonding

Answer 2

• rotation about covalent bonds defines conformation

- changes in configuration require making/breaking of covalent bonds

Question 3

Amphipathic

Answer 3

Molecules that contain both polar and non-polar properties

Question 4

Ionic interactions

Answer 4

-attractive or repulsive electrostatic force
-strength depends on Coulomb’s law: F~q1q2/Dr^2
(D=dielectric constant

Question 5

Van der Waals interactions

Answer 5

• collection of very weak attractive forces due to dipole or induced dipole interactions of closely spaced atoms
• significant in large numbers, where complementary binding surfaces can contribute to biological specificity.

Question 6

Hydrogen bonding

Answer 6

• H shared between two electronegative atoms; partial covalent character
• strength (5-20Kj mol^-1) depends on linearity, and polarity of environment
• very directional: contributes to biological specificity

Question 7

Some biologically important hydrogen bonds

Answer 7

1. Between the hydroxyl group of an alcohol and water
2. between carbonyl group of a ketone and water
3. Between peptide groups in polypeptides
4. Between complementary bases of DNA

H bonds are strongest when the 3 atoms are in line

Question 8

Hydrophobic effect

Answer 8

-the tendency of non-polar substances to aggregate in aqueous solution