1. Why does E. coli need both DNA polymerase III and DNApolymerase I?
a. The DNA replication is bidirectional; one polymerase is usedfor each direction.
b. Each polymerase is specific for only one strand of DNA. DNApolymerase III acts only on the leading strand, and DNA polymeraseI acts only on the lagging strand.
c. Only DNA polymerase I has proofreading ability.
d. DNA polymerase III lacks the 5' → 3' exonuclease activityneeded to remove RNA primers.
2. The replication of DNA is ________ because________.
a. semiconservative; one strand of parental DNA is retained ineach daughter DNA.
b. semiconservative; each daughter molecule has two new strandscopied from the parental DNA template
c. conservative; each daughter molecule has two new strandscopied from the parental DNA template.
d. conservative; one strand of parental DNA is retained in eachdaughter DNA.
3. Active transport proteins in biological membranesare
a. always transporting Ca2+ ions.
b. never driven by concentration gradients.
c. never driven by ATP to ADP conversion.
d. sometimes driven by concentration gradients.
4. Why should it not be surprising that for many cellswater requires a protein for its transport across amembrane?
a. The transport protein is needed to prevent the hydrolysis ofthe phospholipid chains as water crosses the membrane.
b. Water is very polar which inhibits its free diffusion acrossthe membrane.
c. All molecules require transport proteins to cross amembrane.
d. There is never a concentration gradient for water across themembrane to drive its transport.
5. The conversion of pyruvate to lactate in muscles alsocauses the ________.
a. reduction of NAD+.
b. oxidation of NAD+
c. oxidation of NADH
d. reduction of oxygen to water.
6. ATP is a cosubstrate of the enzyme PFK-1. In mostspecies ATP is also an inhibitor of PFK-1 at higher concentrations.Which statement below would provide a suitableexplanation?
a. PFK-1 must be phosphorylated by ATP in the active site andthe phosphorylated PFK-1 must be the less active form.
b. There are two sites on PFK-1 that bind ATP. One is the activesite; the other is the regulatory site where inhibition occursallosterically.
c. ATP actually activates the reverse of the reaction precedingthe PFK-1 step in the pathway. It likely has no direct effect onPFK-1.
d. There must be another cofactor interacting with ATP at highconcentrations to achieve inhibition of PFK-1.
7. Briefly describe two ways for deactivation ofGPCR-signaling.
