BCH 451 TEST 1 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS VERIFIED GRADED A++
Ethanol and polarity
-Ethanol: hydroxyl and ethyl functional groups (the ethyl group is sometimes divided into
separate methyl and methylene components)
-Functional groups: molecular components that serve as tools within chemical reactions
-Polar functional groups: hydrophilic due to its ability to freely and spontaneously
associate with water (hydroxyl)
-nonpolar functional groups: hydrophobic due to its exclusion from a polar, aqueous
solution (ethyl)
-amphipathic: hydrophobic and hydrophilic functional groups (like ethanol)
-INCLUDE IMAGE WITH FUNCTIONAL GROUPS
REDOX reactions
-Oxidation-reduction are reactions in which electrons are transferred from one molecule
to another
,-molecule that donates or loses the electrons: oxidized
-molecule that accepts or receives the electrons: reduced
-require a simultaneous oxidation and reduction event
-electrons must be conserved
-gaining bonds to oxygen (or losing bonds to hydrogen) is indicative of the molecule
becoming oxidized
-Gaining bonds to hydrogen (or losing bonds to oxygen) is emblematic of reduction
-DRAW A REDOX REACTION OF ETHANOL, ACETALDEHYDE, AND ACETATE
Disulfide Bonds and BME
-Beta-mercaptoethanol (BME): amphipathic molecule composed of an ethylene,
hydroxyl, and thiol (or sulfhydryl) functional group
-BME serves as a buffer against the proliferation of disulfide bonds in solution
-disulfide bond: covalent attachment between 2 sulfur atoms
-In proteins, disulfide bonds can only form between 2 cysteine AA residues.
,-2 connected cysteine residues is called cystine
-Formation of a disulfide bond is a redox reaction. The disulfide bond represents the
oxidized state.
-low concentration: BME prevents the formation of new disulfide bonds (below 8 mM)
-high concentrations: BME breaks down existing disulfide bonds (above 8 mM)
-IMAGE OF BME AND A POLYPEPTIDE W AND W/O DISULFIDE BOND
Nucleophilic Attack
-nucleophile: molecule with a negatively charged, electron-rich region capable of
attacking electron vacant, positively charged areas in other molecules
-Nucleophiles contain electron dense regions generally indicative of lone pairs
-Hydroxyls and amine groups are frequently observed nucleophilic functional groups.
-Nucleophiles often have lone pair electrons
-A nucleophilic center is a positively charged, electron-deficient functional group within a
molecule (aka an electrophile)
, -Nucleophilic centers are often carbonyls or phosphoryls, with the highly electronegative
oxygen withdrawing electron density away from the adjacent carbon or phosphorous
-A nucleophilic attack occurs when a negatively charged nucleophile bind covalently to
a positively charged nucleophilic center
-Acetyl phosphate is a typically used example as it contains two nucleophilic centers
(the carbonyl and phosphoryl) and several nucleophilic oxyanions around the phosphate
-IMAGE OF NUCLEOPHILIC CENTER (DO NOT CALL IT AN ELECTROPHILE)
pKa
-The term pKa is derived from Ka, the acid dissociation equilibrium constant
-The pKa = -log Ka
-pKa of a functional group: measures its likelihood to exist in a protonated or
deprotonated state within a solution
-pKa corresponds to a particular functional group rather than a larger molecule
-smaller the pKa value, the more resistant a functional group is to protonation
COMPLETE SOLUTIONS VERIFIED GRADED A++
Ethanol and polarity
-Ethanol: hydroxyl and ethyl functional groups (the ethyl group is sometimes divided into
separate methyl and methylene components)
-Functional groups: molecular components that serve as tools within chemical reactions
-Polar functional groups: hydrophilic due to its ability to freely and spontaneously
associate with water (hydroxyl)
-nonpolar functional groups: hydrophobic due to its exclusion from a polar, aqueous
solution (ethyl)
-amphipathic: hydrophobic and hydrophilic functional groups (like ethanol)
-INCLUDE IMAGE WITH FUNCTIONAL GROUPS
REDOX reactions
-Oxidation-reduction are reactions in which electrons are transferred from one molecule
to another
,-molecule that donates or loses the electrons: oxidized
-molecule that accepts or receives the electrons: reduced
-require a simultaneous oxidation and reduction event
-electrons must be conserved
-gaining bonds to oxygen (or losing bonds to hydrogen) is indicative of the molecule
becoming oxidized
-Gaining bonds to hydrogen (or losing bonds to oxygen) is emblematic of reduction
-DRAW A REDOX REACTION OF ETHANOL, ACETALDEHYDE, AND ACETATE
Disulfide Bonds and BME
-Beta-mercaptoethanol (BME): amphipathic molecule composed of an ethylene,
hydroxyl, and thiol (or sulfhydryl) functional group
-BME serves as a buffer against the proliferation of disulfide bonds in solution
-disulfide bond: covalent attachment between 2 sulfur atoms
-In proteins, disulfide bonds can only form between 2 cysteine AA residues.
,-2 connected cysteine residues is called cystine
-Formation of a disulfide bond is a redox reaction. The disulfide bond represents the
oxidized state.
-low concentration: BME prevents the formation of new disulfide bonds (below 8 mM)
-high concentrations: BME breaks down existing disulfide bonds (above 8 mM)
-IMAGE OF BME AND A POLYPEPTIDE W AND W/O DISULFIDE BOND
Nucleophilic Attack
-nucleophile: molecule with a negatively charged, electron-rich region capable of
attacking electron vacant, positively charged areas in other molecules
-Nucleophiles contain electron dense regions generally indicative of lone pairs
-Hydroxyls and amine groups are frequently observed nucleophilic functional groups.
-Nucleophiles often have lone pair electrons
-A nucleophilic center is a positively charged, electron-deficient functional group within a
molecule (aka an electrophile)
, -Nucleophilic centers are often carbonyls or phosphoryls, with the highly electronegative
oxygen withdrawing electron density away from the adjacent carbon or phosphorous
-A nucleophilic attack occurs when a negatively charged nucleophile bind covalently to
a positively charged nucleophilic center
-Acetyl phosphate is a typically used example as it contains two nucleophilic centers
(the carbonyl and phosphoryl) and several nucleophilic oxyanions around the phosphate
-IMAGE OF NUCLEOPHILIC CENTER (DO NOT CALL IT AN ELECTROPHILE)
pKa
-The term pKa is derived from Ka, the acid dissociation equilibrium constant
-The pKa = -log Ka
-pKa of a functional group: measures its likelihood to exist in a protonated or
deprotonated state within a solution
-pKa corresponds to a particular functional group rather than a larger molecule
-smaller the pKa value, the more resistant a functional group is to protonation
