Biochemistry Exam I

Question 1

electronegativity

Answer 1

a measure of the force of an atom’s attraction for electrons it shares in a chemical bond with another atom.

Question 2

amphipathic molecules

Answer 2

both polar and non-polar character; interaction between non-polar molecules is very weak (Van der Waals)

Question 3

origin of the hydrophobic effect

Answer 3

lipid molecule forces surrounding H₂O molecules to become highly ordered; low entropy; unfavored; (important in protein folding)

Question 4

micelle

Answer 4

a spherical arrangement of organic molecules in water solution clustered so that their hydrophobic parts are buried inside and hydrophilic parts are on surface of the sphere; formation depends on attraction between temporary induced dipoles; used in drug delivery systems (i.e. extended release)

Question 5

Ka equation

Answer 5

Acid strength

Ka = [H+][OH-]/[H₂O]

Question 6

pH equation

Answer 6

pH = -log₁₀[H+]

pH + pOH = 14

Question 7

buffer range

Answer 7

a buffer is effective in a range of about +/- 1 pH unit of the pKa of the weak acid:

Question 8

Beer’s law

Answer 8

log(I0/I1) = εcl = Absorbance (A)

ε -> extinction coefficient

Question 9

strong acids/bases

Answer 9

disassociate 100% in water; no equilibrium

Question 10

weak acids/bases

Answer 10

dissociate <100%, equilibrium is established

Question 11

Henderson-Hasselbalch Equation

Answer 11

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

Question 12

Gibbs free-energy change (∆G)

Answer 12

∆G = ∆H - T∆S
G = Free energy content of a closed system
H = enthalpy (reflects number and types of bonds)
S = entropy
T = absolute temperature
∆G negative - spontaneous - exergonic
∆G positive - non-spontaneous - endergonic

Question 13

Beer’s Law

Answer 13

log(I0/I1) = εcl = Absorbance (A)

ε -> extinction coefficient