ACS Biochemistry Final Exam Questions
And Answers (Guaranteed A+)
pKa (chapter 3) - answer✔measure of the tendency of a group to give up a proton (acidity);
tendency decreases tenfold as pKa increases by one unit
thioester bond (1) - answer✔compounds with functional group C-S-CoA-C (eg, in acetyl-CoA)
zwitterion (3) - answer✔dipolar ion with both positive and negative groups but overall neutral
charge; can act as either an acid or base
Isoelectric point (pI) (chapter 3) - answer✔the characteristic pH at which the net electric charge
is zero
SDS - Sodium Dodecyl Sulfate (chap 3) - answer✔detergent used to unfold proteins and give
them uniform negative charge
SDS Page (3) - answer✔chromatography used to separate proteins based on mass. light
proteins travel fast than heavier ones
PCR - Polymerase chain reaction (3) - answer✔copies DNA multiple times to increase sample
size
Isoelectric focusing (chapt 3) - answer✔procedure used to determine the isoelectric pt (pI) of a
protein. Protein migrates through gel until pH = pI (net charge = 0)
Two-Dimensional Electrophoresis (3) - answer✔combines isoelectric focusing and SDS
electrophoresis; separates proteins by both molecular weight and pI
specific activity (3) - answer✔number of enzyme units per mg of total protein (a measure of
enzyme purity)
activity (3) - answer✔total units of a certain enzyme in a solution
Peptide bonds (chapter 4) - answer✔C-N bond with double bond character due to resonance
(C-N bond cannot rotate, and is planar)
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Edman degredation (3) - answer✔used in the sequencing of polypeptides; labels and removes
ONLY the amino-residue from a polypeptide. carried out in a machine called a sequenator
φ in peptide bonding (chapter 4) - answer✔angle around the α-carbon - amide nitrogen bond
ψ in peptide bonding (chapter 4) - answer✔angle around the α-carbon - carbonyl carbon bond
Ramachandran Plot (4) - answer✔shows favoreable φ-ψ angle combinations. 3 main "wells" for
α-helices, β-sheets, and left handed α-helices
Levinthal's Paradox (4) - answer✔protein folding cannot be a completely random, trial and
error process
chaperonins (4) - answer✔elaborite protein complexes required for the folding of a number of
cellular proteins that do not fold spontaneously
which amino acids are not found in α-helices? (4) - answer✔glycine and proline. glycine is too
flexible, proline is too rigid to rotate.
which amino acids are commonly found in β turns? (4) - answer✔glycine, because it is small and
flexible, and proline because it forms cis conformation in tight turns.
circular dichroism (4) - answer✔technique that measures the amount of helical structures in
macromolecule (protein is denatured)
Acid Dissasociation constant Ka (2) - answer✔quantitative measure of the strength of an acid in
solution
Native Fold - answer✔
Size-exclusion chromatography (3) - answer✔Separates proteins according to size. Large
proteins emerge from the column before small ones (counterintuitive result). The solid phase
consists of beads with engineered pores or cavities of a particular size. Large proteins cannot
enter the cavities, and so take a short (and rapid) path through the column, around the beads.
Small proteins enter the cavities, and migrate through the column more slowly as a result
Affinity chromatography (3) - answer✔based on the binding affinity of a protein. The beads in
the column have a covalently attached chemical group. A protein with affinity for this particular
chemical group will bind to the beads in the column, and its migration will be retarded as a
result
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