An atom has six protons and eight neutrons. Its atomic mass is __________ atomic mass units
a. two
b. four
c. six
d. eight
e. fourteen
E
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Many introduced species have deleterious effects on
communities and ecosystems because a. coevolved parasites and competitors are absent. b. the introduced species are long-lived. c. predators prefer the introduced species; therefore, the local prey proliferate to dangerously high levels. d. the communities from which they came lost an important predator, competitor, or parasite. e. all of these occur.
Some researchers have hypothesized that type II diabetes mellitus is caused by a mitochondrial defect. Which of the following would be the best way for them to study mitochondrial differences in fresh tissue samples from diabetic and nondiabetic mice?
A) Mitochondria could be identified and isolated from other cellular components using immunofluorescence microscopy in both tissues. B) Mitochondria are the only organelles that survive tissue homogenization, thus both tissues could be homogenized to study the mitochondria. C) Mitochondria from both tissues could be isolated from other cellular components by using proteolytic enzymes to break down other cellular structures. D) Mitochondria from both tissues could be isolated from other cellular components by fractionating tissue homogenate using differential centrifugation followed by density gradient centrifugation. E) Mitochondria can not be separated from whole cells without damaging them.
Which of the following is not true of van der Waals interactions?
A. The interaction depends on the distance between atoms. B. Attractive and repulsive forces are balanced at the van der Waals radii for each atom. C. Repulsive interactions arise when atoms are separated by a distance equal to the sum of their combined van der Waals radii. D. Atoms that are farther apart than the sum of their combined van der Waals radii do not experience van der Waals forces. E. All of these statements are true.
Many of the burrowing animals of the mud flat must actively
a. keep digging to exchange gasses. b. circulate water through their burrows. c. live near natural breaks in the sediment for gas exchange. d. maintain an anaerobic environment.