Which of the following describes how facilitated diffusion is powered?
a. Facilitated diffusion is "free of cost."
b. Energy is required to do the work of establishing and maintaining a concentration
gradient.
c. ATP is required directly.
d. The sodium-potassium pump powers facilitated diffusion.
e. Facilitated diffusion is powered by endocytosis
B
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One hypothesis on the origin of DNA points to RNA viruses evolving a modified nucleotide that is insensitive to ribonucleases
Indicate whether the statement is true or false.
Quality control is performed to test the validity of catalase production at 68°C. M. fortuitum and M. tuberculosis are used, which yield a positive and negative reaction, respectively. Which one of the following statements explains this discrepancy?
a. Both organisms were most likely incu-bated at the wrong temperature. b. Both organisms were most likely incu-bated on the wrong media before testing. c. The catalase reagent is most likely expired. d. No discrepancy is present. M. fortuitum is catalase-positive and M. tuberculosis is catalase-negative at 68°C.
The sugar "sink" in roots is the result of
A) active transport of mineral ions into xylem cells. B) absorption of water from the soil through epidermal cells. C) active transport of sugars from phloem to root cells. D) the pull of gravity on sugar molecules.
The genes for purple eyes and curved wings are approximately 21 map units apart on chromosome II in Drosophila. Assume that a purple-eyed female was mated to a curved wing male and that the resulting F1 phenotypically wild-type females were mated to
purple, curved males. Of 1000 offspring, what would be the expected number of flies with purple eyes and curved wings? A) 210 B) 540 C) 790 D) 105 E) 395