Biochemistry Flashcards
Which of the following are the most important determinants of the electrophoretic mobility of amino acids?
a. Temperature and pressure
b. Buffer concentration and net charge
c. Net charge and molecular weight
d. Molecular weight and buffer concentration
c. Net charge and molecular weight
Which of the following interactions is NOT typically involved in mediating reversible binding of macromolecules with their ligands?
a. Covalent bonding
b. Ionic interactions
c. Hydrophobic interactions
d. Hydrogen bonding
Covalent bonding
Which of the following terms refer(s) to the purely protein component of an enzyme?
a. apoenzyme
b. coenzyme
c. holoenzyme
d. all of the above
a. apoenzyme
An enzyme is isolated with an inhibitor within its active site. The inhibitor is not covalently linked to the enzyme and is structurally similar to the natural substrate of the enzyme. What procedure would most likely result in recovery of the active enzyme?
a. Application of heat
b. Treatment with organic solvents
c. Addition of a strong acid
d. Addition of the natural substrate
d. Addition of the natural substrate
Under which of the following categories of enzymes are trypsin and most other digestive enzymes classified?
a. Hydrolases
b. Isomerases
c. Lyases
d. Oxidoreductases
A. Hydrolases
Which of the following statements best describes the action of a ligase?
a. It catalyzes the transfer of electrons
b. It catalyzes the transfer of functional groups from one substrate to another
c. It catalyzes the rearrangement of atoms within a single substrate
d. It catalyzes the covalent linkage of molecules accompanied by the cleavage of a high-energy bond (e.g. a phosphoanhydride bond of ATP)
D. It catalyzes the covalent linkage of molecules accompanied by the cleavage of a high-energy bond (e.g. a phosphoanhydride bond of ATP)
Which of the following statements is/are TRUE regarding the Michaelis-Menten constant Km?
a. Km is equal to the concentration of substrate at half-saturation
b. Km is more similar to an association constant than dissociation constant
c. Km tends to increase as the affinity between enzyme and substrate increases
d. A and B only
a. Km is equal to the concentration of substrate at half-saturation
Which of the following cofactors function(s) as carrier(s) of amino groups in enzyme-catalyzed transamination reactions?
a. Biotin
b. Heme
c. Pyridoxal phosphate
d. A and B only
c. Pyridoxal phosphate
Which of the following features is typical of reversive competitive inhibition?
a. Apparent decrease in Km
b. Binding of the inhibitor to allosteric sites
c. Covalent bond formation between the enzyme and the inhibitor
d. Reversal of inhibition by addition of excess substrates
d. Reversal of inhibition by addition of excess substrates
Which of the following features BEST distinguishes DNA from RNA?
a. DNA contains thymine while RNA contains uracil
b. DNA has a greater mass per base pair than RNA
c. DNA is double-stranded while RNA is single-stranded
d. DNA is less susceptible to base-catalyzed hydrolysis than RNA
Which of the following processes is directly affected by a compound that specifically inhibits RNA-dependent DNA polymerase?
a. DNA replication
b. Transcription
c. Reverse transcription
d. RNA replication
A.
DNA replication
Which of the following statements best describes the degeneracy of the genetic code?
a. For every codon there exists a tRNA bearing a corresponding anticodon
b. More than one codon can code for the same amino acid residue
c. The genetic code has decreased in complexity through evolution
d. The genetic code is unstable, changing from one generation to the next
b. More than one codon can code for the same amino acid residue
The chemical warfare agent sarin and the insecticide malathion both inhibit the enzyme acetylcholinesterase by forming a covalent bond with the oxygen atom of serine residue within the active site. Which of the following types of enzyme inhibition does this process exemplify?
a. Irreversible inhibition
b. Reversible competitive inhibition
c. Reversible noncompetitive inhibition
d. Reversible uncompetitive inhibition
a. Irreversible inhibition
