polar and nonpolar interactions

Question 1

dielectric constant

Answer 1

• way to measure magnitude of attraction between charges.
• for a solvent, what numerical value defines how good of an insulator the solvent can be around charges

Question 2

higher dielectric constant number

Answer 2

higher number = weaker interaction (insulated from seeing each other)
lower number = the atoms will sense each other

Question 3

examples of dielectric constants

Answer 3

Water (80) can solvate (insulate) ions better than nonpolar organic liquids (1-10)

Question 4

why does water have a higher dielectric constant

Answer 4

hydration shell surrounds and shields ions (molecules) thus isolating the charges and enabling good solubility

Question 5

what happens if both nonpolar (hydrophobic) and polar (hydrophilic) features are present?

Question 6

biological macro-ions

Answer 6

poly-ampholytes that can act as acids or bases and with sizeable net charge (about 3+)

Question 7

what occurs when like charges attract?

Answer 7

Aggregations form, which create protein clumps…. not healthy, diseases…..

Question 8

what occurs when like charges repel?

Answer 8

at pH above or below pI, molecules are usually soluble

Question 9

pI

Answer 9

pH at which molecule has no net charge… zwitterion is present

Question 10

WHat happens when molecule is at the pI?

Answer 10

the molecule is not soluble, due to the no net charge… this is why you can separate proteins by knowing their pI…. the protein will drop out of solution at their pI

Question 11

Counterions

Answer 11

have influence on macromolecular interactions… if you surround a protein with a negative charge by positivdly charged counterions, that will affect the ability of the aggregates to form… will make them less likely to form.