Waters and Buffers

Question 1

Define amphipathic

Answer 1

contains regions that are polar (charged, hydrophilic) and regions that are nonpolar (hydrophobic)

Question 2

How are lipids dispersed in water?

Answer 2

Each lipid molecule forces surrounding H2O molecules to become highly ordered. Only lipid portions at the edge of the cluster force the ordering of water. Fewer H2O molecules are ordered and entropy is increased. All hydrophobic groups are sequestered from water, ordered shell of H2O molecules is minimized, and entropy is further increased.

Question 3

Describe the role of water in protein/DNA structure, binding and catalysis.

Answer 3

Water is driving structure, interactions, and forces within the cell. (ex. ordered water interacts with substrate and enzyme binding, and disordered water is displaced by enzyme-substrate interaction)

Question 4

What is the acid dissociation constant (Ka)?

Answer 4

Describes the extent of dissociation of an acid. Ka = [H+] [A-] / [HA] (the larger the Ka the stronger the acid).

Question 5

What is the pKa?

Answer 5

Indicates the strength of an acid/ a measure of dissociation. pKa = -log Ka. (strong acid –> large Ka –> small pKa). Indicates buffering capacity as well.

Question 6

What is the Henderson-Hasselbalch equation?

Answer 6

pH = pKa+log [A-]/[HA]

Question 7

What is a buffer?

Answer 7

Mixtures of weak acids and their anions (conjugate base). They resist change in pH because an equilibrium between the buffer components is established.

Question 8

What are some examples of biological buffers?

Answer 8

Dihydrogen-phosphate buffering system (intracellular pH). Carbonic acid buffering system (blood). Proteins.