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Biochem ACS review study guide Questions and Answers Graded A+
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Biochem ACS review study guide
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Biochem ACS review study guideWhich of the following statements about collagen is correct?
a) Collagen contains a high proportion of hydroxylated proline residues.
b) Collagen is a globular, intracellular protein.
c) Post-translational modification of collagen involves vitamin A.
d) The structure of collagen consists of a superhelix of three α helices twisted together -
answera) Collagen contains a high proportion of hydroxylated proline residues.
Explanation - collagen has α chains, NOT helices. Each of the polypeptides in the triple
superhelix of procollagen is an unusual left-handed helix not the right-handed α helix
seen in globular proteins. However, the three polypeptides are twisted around each
other in a righthanded manner to form the triple helix. All α helices are right-handed and
get broken from high amounts of proline, hydroxylated proline, and glycine; but, these
triplets of amino acids strength collagen. Glycine-X-Y.
2. Which of the following polypeptides is expected to be a globular protein?
a) KFSCCKDVVDG
b) IPVDSEDKHWY
c) AFSCKHEDGML
d) RDGLIVFYWSC
e) DEHRKICLRRG - answerd) RDGLIVFYWSC
Explanation - Utilize the one letter codes for all amino acids and know their charge and
polarity. Globular proteins are usually seen in aqueous environments and will fold to
have nonpolar amino acids on its interior. Based on that information, the polypeptide
needs to have outside amino acids that are charged or polar while the interior will have
nonpolar/hydrophobic amino acids. D is correct because (RDGLIVFYWSC) arginine,
aspartate, serine, and cysteine are polar/charged.
Which amino acid(s) have an acidic side chain? - answeraspartate
Which amino acid(s) are non-chiral? - answerglycine
Which amino acid(s) have a basic side chain? - answerlysine
Which amino acid(s) have a side chain that can be modified by adding phosphates? -
answerserine and tyrosine
Which amino acid(s) are involved in disulfide cross links? - answercysteine
Which amino acid(s) are often found in the turns of proteins? - answerglycine and
proline
, Which amino acid(s) are converted to tyrosine by hydroxylation? - answerphenylalanine
Which amino acid(s) are important in the structure in collagen? - answerlysine and
proline
Which amino acid(s) have more than one amino group? - answerlysine and asparagine
Which amino acid(s) have an overall net charge of -2 at pH 7.4? - answernone
Which amino acid(s) have only straight or branched hydrocarbons in side chain? -
answerleucine
Which amino acid(s) have a polar, non-charged side chain? - answerserine, asparagine,
tyrosine, and cysteine
Which amino acid(s) have an aromatic side chain? - answerphenylalanine, tyrosine,
tryptophan
Where are Pro & Glycine seen in proteins? - answerBeta sheets (for turns) and
collagen.
Can these AA be used for α-helices? - answerNo. Due to Proline's N involved in the
ring, it is too rigid for a N-Cα bond (makes kink) & N doesn't have hydrogen bond. For
Glycine, too much flexibility; more likely to be seen in a coiled-coil structure (collagen)
explanation for questions 3-17 - answerExplanation - 6: Follow-up question: Where are
Pro & Glycine seen in proteins? Ans: Beta sheets (for turns) and collagen. Can these
AA be used for α-helices? Ans: No. Due to Proline's N involved in the ring, it is too rigid
for a N-Cα bond (makes kink) & N doesn't have hydrogen bond. For Glycine, too much
flexibility; more likely to be seen in a coiled-coil structure (collagen) 8: Lys increases
tensile strength by cross-linking between α chains. This may not be common knowledge
about Lys. During the ACS Review, I did not go over this. 10. There are amino acids
that have a -2 charge at physiological pH. If it said -1, then the acidic amino acids would
be correct. 12. Technically tyrosine is a polar, non-charged side chain, but through GCU
we are taught that it is aromatic. During ACS Review, this was not added to the list.
The amino acid most likely to yield the above titration curve above would be?
a) Arginine
b) Glutamic acid
c) Glycine
d) Methionine
e) Tyrosine - answera) Arginine
Explanation - Based on the location where pI is, the amino acid is basic (due to it having
a basic pH). The only possible answer that is a basic amino acid is arginine. Know the
properties of all amino acids and how to calculate pI from a titration curve. From pI, you
should be able figure out the amino acid the titration curve corresponds with.
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