BCH 369 EXAM with Questions Solved 100%
Correct | Latest Update
Rationalize the fact that hydrogen bonding has not been observed between CH4
molecules - Answer The C-H bond is not sufficiently polar for greatly unequal
distribution of electrons at its two ends. Also, there are no unshared pairs of electrons
to serve as hydrogen bond acceptors
What are the requirements for molecules to form hydrogen bonds? - Answer A
hydrogen covalently bonded to a O, N or F. This hydrogen then forms a hydrogen bond
with another O, N, or F.
Both RNA and DNA have negatively charged phosphate groups as part of their structure.
Would you expect ions that bind to nucleic acids to be positively or negatively charged?
Why? - Answer Positively charged ions bind to nucleic acids as a result of electrostatic
attraction to the negatively charged phosphate groups.
Aspirin has a pKa of 3.5 w/ carboxyl group. Would it be more absorbed in stomach w/
pH = 1 or small intestine with pH = 6? - Answer Small intestine since it is neutral in the
stomach and will more easily pass through until the small intestine.
Why does the pH change by one unit if the hydrogen ion concentration changes by a
factor of 10? - Answer The definition of pH is -log[H^+]. By definition of the log function,
a change in concentration of 10 leads to a change in pH of 1. The log of 10 is 1, the log of
100 is 2
what is the relationship between the pka and the useful range of a buffer? - Answer The
useful pH rang of a buffer is one pH unit above an below its pKa.
How do D-amino acids differ from L-amino acids? Which amino acid contains no chiral
carbon atoms? - Answer D and L amino acids have different stereochemitry around the
, alpha-carbon. Peptides that contain D-amino acids are found in bacterial cell walls and
in some antibiotics
Which amino acid is technically not an amino acid? Which amino acid contains no chiral
carbon atoms? - Answer Proline is technically not an amino acid. Glycine contains no
chiral carbon atoms.
For each of the following, name an amino acid in which the R group contains it: a
hydroxyl group, a sulfur atom, a second chiral carbon atom, an amino group, an amide
group, an acid group, an aromatic ring, and a branched side chain. - Answer Hydroxyl
group: Serine, Threonin, Tyrosine
Sulfur atom: Cysteine or Methionine
Second chiral carbon atom: isoleucine or threonine
Amino group: Lysine
Acid group: Aspartate or glutamate
Aromatic ring: Phenylalanine, tyrosine, tryptophan
Branched side chain: Leucine or valine
identify the polar amino acids, the aromatic amino acids and sulfur-containing amino
acids given:
Val-Met-Ser-Ile-Phe-Arg-Cys-Tyr-Leu - Answer Polar amino acids: Ser, Arg, Cys, Tyr
Aromatic: Phe and Tyr
Sulfur containing: Met and Cys
Identify the non polar amino acids and the acidic amino acids:
Glu-Thr-Val-Asp-Ile-Ser-Ala - Answer Nonpolar: Val, Ile, Ser, Ala
Acidic: Asp, Glu
Polar: Thr
Correct | Latest Update
Rationalize the fact that hydrogen bonding has not been observed between CH4
molecules - Answer The C-H bond is not sufficiently polar for greatly unequal
distribution of electrons at its two ends. Also, there are no unshared pairs of electrons
to serve as hydrogen bond acceptors
What are the requirements for molecules to form hydrogen bonds? - Answer A
hydrogen covalently bonded to a O, N or F. This hydrogen then forms a hydrogen bond
with another O, N, or F.
Both RNA and DNA have negatively charged phosphate groups as part of their structure.
Would you expect ions that bind to nucleic acids to be positively or negatively charged?
Why? - Answer Positively charged ions bind to nucleic acids as a result of electrostatic
attraction to the negatively charged phosphate groups.
Aspirin has a pKa of 3.5 w/ carboxyl group. Would it be more absorbed in stomach w/
pH = 1 or small intestine with pH = 6? - Answer Small intestine since it is neutral in the
stomach and will more easily pass through until the small intestine.
Why does the pH change by one unit if the hydrogen ion concentration changes by a
factor of 10? - Answer The definition of pH is -log[H^+]. By definition of the log function,
a change in concentration of 10 leads to a change in pH of 1. The log of 10 is 1, the log of
100 is 2
what is the relationship between the pka and the useful range of a buffer? - Answer The
useful pH rang of a buffer is one pH unit above an below its pKa.
How do D-amino acids differ from L-amino acids? Which amino acid contains no chiral
carbon atoms? - Answer D and L amino acids have different stereochemitry around the
, alpha-carbon. Peptides that contain D-amino acids are found in bacterial cell walls and
in some antibiotics
Which amino acid is technically not an amino acid? Which amino acid contains no chiral
carbon atoms? - Answer Proline is technically not an amino acid. Glycine contains no
chiral carbon atoms.
For each of the following, name an amino acid in which the R group contains it: a
hydroxyl group, a sulfur atom, a second chiral carbon atom, an amino group, an amide
group, an acid group, an aromatic ring, and a branched side chain. - Answer Hydroxyl
group: Serine, Threonin, Tyrosine
Sulfur atom: Cysteine or Methionine
Second chiral carbon atom: isoleucine or threonine
Amino group: Lysine
Acid group: Aspartate or glutamate
Aromatic ring: Phenylalanine, tyrosine, tryptophan
Branched side chain: Leucine or valine
identify the polar amino acids, the aromatic amino acids and sulfur-containing amino
acids given:
Val-Met-Ser-Ile-Phe-Arg-Cys-Tyr-Leu - Answer Polar amino acids: Ser, Arg, Cys, Tyr
Aromatic: Phe and Tyr
Sulfur containing: Met and Cys
Identify the non polar amino acids and the acidic amino acids:
Glu-Thr-Val-Asp-Ile-Ser-Ala - Answer Nonpolar: Val, Ile, Ser, Ala
Acidic: Asp, Glu
Polar: Thr
