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)
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
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
HPLC, or high-performance liquid chromatography. - answer✔pumps speed the movement of
the protein molecules down the column, as well as higher-quality chromatographic materials
that can withstand the crushing force of the pressurized flow. By reducing the transit time on
the column, HPLC can limit diffusional spreading of protein bands and thus greatly improve
resolution.
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