MCAT- Biological and Biochemical Foundations of Systems
|| with Complete Solutions.
messenger RNA (mRNA) is synthesized in what direction and is complementary and antiparallel
to which DNA strand (coding or template)? correct answers synthesized in the 5'-->3' direction
and is complementary and antiparallel to the DNA template strand. It is identical to the DNA
coding strand.
How are the basal layer of the epidermis and the innermost lining of the small intestine similar?
A. both are nondividing tissues
B. both are derived from ectoderm
C. both are composed of squamous cells
D. the cells of both are connected by tight junctions correct answers D
Starting with the translation initiation codon, the following sequence encodes a polypeptide of
how many amino acids?
5'-CUGCCAAUGUGCUAAUCGCGGGGG-3'
A. 2
B. 3
C. 6
D. 8 correct answers A
Sodium dodecyl sulfate (SDS) contains a 12-carbon tail attached to a sulfate group and is used in
denuaturing gel electrophoresis of proteins. Numerous SDS molecules will bind to the exposed
hydrophobic regions of denatured proteins. The use of SDS in this experiment allows for the
separation of proteins by:
A. charge
B. molecular weight
C. shape
D. solubility correct answers B
Which is true about the oxygen binding of hemoglobin at different pH values?
A. Low pH favors the high affinity oxygen binding state
B. Low pH favors the low affinity oxygen binding state
C. Oxygen affinity is independent of pH
D. Oxygen binding is non-cooperative at low pH correct answers B
define amino acids correct answers molecules that contain two functional groups: an amino
group (-NH2) and a carboxyl group (-COOH)
in alpha (a) amino acids, are the amino and carboxyl group are bonded to the same carbon or
opposite carbons? correct answers the same carbon
what is the one exception to the rule that amino acids are chiral? correct answers glycine which
has a H side chain
,all chiral amino acids used in eukaryotes are? correct answers L-amino acids
Almost all chiral amino acids are in the R or S configuration? What is the one exception? correct
answers S. Except cysteine which is R
the side chains (R groups) of amino acids determine what? correct answers their chemical
properties
which amino acids are strongly hydrophobic? where are they most likely to be in the body?
correct answers the amino acids with long alkyl side chains: alanine, isoleucine, leucine, valine,
and phenylalanine.
found in the interior of proteins, away from water on the surface of the protein
which amino acids are hydrophilic? correct answers amino acids with charged side chains:
histidine, arginine ,lysine, glutamate and aspartate, as well as the amides: asparginine and
glutamine
Alanine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Ala, A,
nonpolar
Arginine: 3 letter abbreviation, 1 letter abbreviation correct answers Arg. R
Asparginine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Asn.
N. Polar
Aspartic acid: 3 letter abbreviation, 1 letter abbreviation correct answers Asp. D
Cysteine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Cys. C.
Polar
Glutamic Acid: 3 letter abbreviation, 1 letter abbreviation correct answers Glu. E.
Glutamine. 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Gln. Q.
Polar
Histidine: 3 letter abbreviation, 1 letter abbreviation correct answers His. H.
Isoleucine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Ile. I.
Non-polar
Leucine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Leu. L.
Non-polar
Lysine: 3 letter abbreviation, 1 letter abbreviation correct answers Lys. K.
,Methionine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Met.
M. Non-polar
Phenylalanine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Phe.
F. Non-polar
Proline: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Pro.P.
Non-polar
Serine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Ser. S.
Polar
Threonine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Thr. T.
Polar
Tryptophan: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Trp.
W
Tyrosine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Tyr. Y.
Polar
Valine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Val. V.
Non-polar
Glycine: 3 letter abbreviation, 1 letter abbreviation, polar or non polar correct answers Gly. G.
Non-polar
what are amphoteric species? correct answers they can either accept or donate a proton (such as
an amino acid). how they react depends on the pH of their environment
Ionizable groups tend to ____ protons under acidic conditions and ___ them under basic
conditions. So, in general, at low pH, ionizable groups tend to be _______, at high pH they tend
to be _____. correct answers gain- acidic
lose- basic
low pH- protonated
high pH- deprotonated
The pKa of a group is what?
If the pH is less than the pKa, a majority of the species will be ______.
If the pH is more than the pKa, a majority of the species will be ______. correct answers the pH
at which, on average, half o f the molecules of that species are deprotonated.
[protonated version of the ionizable protein]=[deprotonated version]
[HA]=[A-]
pH < pKa. protonated
pH > pKa. deprotonated
, In amino acids, the pKa for the carboxyl group is around _____.
The pKa for the amino group is around _____. correct answers carboxyl group: pKa=2
amino group: pKa= 9-10
what is a zwitterion? correct answers a zwitterion is a species with both a positive and a negative
charge
At very acidic pH values, amino acids tend to be _______charged.
At very basic pH values, amino acids tend to be _______charged. correct answers acidic. +
charge
basic. - charge
When the pH of a solution is approximately equal to the pKa of the solute, the solution acts as
what? correct answers a buffer
When pH of an amino acid equals the isoelectric point (pI) of the amino acid, what does this tell
us? correct answers it exists as electrically neural molecules
When titrating glutamic acid, where do the 1st and 2nd protons losses come from? correct
answers Glutamic acid has 2 carboxyl groups and 1 amino group. The 1st comes from the main
carboxyl group, and the 2nd comes from the 2nd carboxyl group NOT the amino group!
When titrating lysine, where do the 1st and 2nd proton losses come from? correct answers Lysine
has 2 amino groups and 1 carboxyl group. The 1st comes from the carboxyl and the 2nd comes
from the amino.
For amino acids with non-ionizable side chains, the pI is usually around ___. Amino acids with
acidic side chains have pI values around what; basic side chains have
pI values around what? correct answers non-ionizable: 6
acidic: well below 6
basic: well above 6
peptides are composed of what? correct answers amino acid subunits, sometimes called residues
dipeptides consist of what? tripeptides? oligopeptides? polypeptides? correct answers dipeptide-
2 amino acid residues
tripeptide- 3 amino acid residues
oligopeptides- 4-20 residues
polypeptides- 21+ residues
peptides are joined by what? which forms between what 2 things? correct answers peptide bonds,
which forms between the -COO- group of one amino acid and the NH3+ group of another amino
acid
