Biochemistry Exam 1 questions with complete solutions.
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Biochemistry
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Biochemistry
how do amino acids differ from one another?
shape, charge, size, hydrogen-bonding character, chemical reactivity, and hydrophobic character
collagen is a major protein in connective tissue of vertebrates. it consists of three left-handed helical chains coiled around each other in a right-hand...
biochemistry exam 1 questions with complete solutions
how do amino acids differ from one another
collagen is a major protein in connective tissue of vertebrates it consists of three left handed hel
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Biochemistry Exam 1
how do amino acids differ from one another? - Answer shape, charge, size, hydrogen-
bonding character, chemical reactivity, and hydrophobic character
collagen is a major protein in connective tissue of vertebrates. it consists of three left-
handed helical chains coiled around each other in a right-handed super-coil.
what vitamin is required for collagen formation?
the vitamin is required for what - Answer Vitamin C and hydroxylation reaction
immunoglobin is critical for bodys defense. will addition of beta-mercaptoethanol perturb
its structure? - Answer yes because it reduces disulfide bonds that are involved in
Quaternary structure
an enzyme accelerates the rate of a reaction by what? - Answer decrease the reaction
activation energy
if you were to design a small peptide with a large number of net negative charges at
physiological pH (around 7), which amino acid residues should predominate - Answer
Glu and Asp
lineweaver-burk plot is a linear transformation of the michaelis-menten plot. what is it
used for? - Answer it is used to calculate Km and Vmax
what properties distinguish enzymes from other catalysts - Answer it is highly efficient,
specific, regulated, and under mild conditions
what is the key initial driving force in protein folding - Answer the peptide folds in such a
way to maximize interactions between hydrophobic amino acids
what mechanism is respondible for denaturation of a protein by each of the following
changes:
a) decrease pH to 2.0 and b) mercury compounds - Answer decrease pH to 2.0 disrupts
salt bridges
mercury compounds react with sulfhydryl groups of crysteine and disrupt disulfide
bonding
this reaction is catalyzed by what class of enzyme?
pruvate + H == acetaldehyde + carbon dioxide - Answer lyase
what is the nucleotide used for in DNA sequencing? - Answer dideoxynucleotide, it is
used to randomly terminate DNA replication by DNA polymerase. the identities of the
terminator nucleotides of successive fragments reveal the original DNA sequence
, what does "hydrophobic effect" refer to - Answer nonpolar molecules have a tendency
to aggregate in water to minimize their contact with water
suppose that you were analyzing the subunit composition of your favorite protein. using
gel filtration, you found that the protein gave one protein peak at a molecular mass 600
kD. when the protein was subjected to SDS-PAGE, it gave three protein bands on the
gel with the apparent molecular mass of 100 kD, 80 kD and 120 kD. how many
polypeptides is the protein composed of? explain why different molecular masses were
observed with the two techniques - Answer 6 polypeptides
gel filtration detects protein size in its native form, whereas SDS-PAGE denatures
proteins and breaks polypeptide interactions
describe three key features of an alpha helix of a polypeptide - Answer the alpha helix is
coil stabilized by intrachain hydrogen bonds. there are 3.6 amino acids per turn. the
hydrogen bonds are between amino acids that have two intervening amino acids, thus
the first is bonded to the (n+4) fourth reside, and these amino acids are found on the
same side of the coil. the helix is almost always right-handed
casein, the main protein in milk, is a phosphorylated protein. the pI of casein is about
4.6 and the pH of milk is around 6.6.
a) is casein positively or negatively charge in milk?
b) when milk sours, the milk clots because of what
C) phospho-groups are added to what amino acids of casein - Answer a) negatively -
COO- and _PO32-
b) casein precipitates from solution due to lowering pH to its pI at which casein
becomes the least soluble
c) Ser, Thr, Tyr
does a reaction with delta H = 10 kJ/mol and delta S = 100 j?K*mol at 27 degrees C,
occur spontaneously or not? - Answer yes becuase gibbs free energy change is
negative
what is the function of molecular chaperones - Answer chaperones increase rate of
correct protein folding and prevent the formation of incorrectly folded intermediates
for Arg, pK1 (a-COOH)=1.82 pK2 (a-NH3)=9.0, pKr (side chain)=12.48
a) what is the net charge of the predominant form of Arg at pH 7?
b) at what pH does Arg carry no net charge? - Answer a) +1
b) pI= (pK2+pKr)/2=10.74
list all the basic categories of enzymes - Answer there are six categories, which include
Oxidoreductases (oxidation-reduction reactions), transferases (group transfers),
Hydrolases (hydrolysis reactions), Lyases (addition or removal of across a double
bond), Isomerases (intramolecular group transfer), and Ligases (ATP-dependent
ligation of substrates)
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