Which of the following statements is true about the net movement of an ion across a membrane by passive diffusion through a membrane channel?
a. For every ion that diffuses through the membrane, a different ion diffuses in the opposite direction.
b. The cell expends energy as the ion passes through the membrane.
c. The charge on the other side of the membrane is generally the opposite of the ion's charge.
d. There is a higher concentration of ions on the side of the membrane toward which the ion diffuses.
Answer: c. The charge on the other side of the membrane is generally the opposite of the ion's charge.
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When a farmer grows cotton containing the gene for Bt toxin, insects that are resistant (rr) survive and reproduce. This is an example of
A. genetic drift. B. dominance. C. natural selection. D. recombination. E. independent assortment.
Why is cancer more prevalent in older individuals?
a. Cancer cells form at a faster rate. b. More mutations develop with age. c. The protective action of cytotoxic T cells breaks down with age. d. Cancers learn to disguise themselves as "self" with time. e. Older people tend to be exposed to more dangerous chemicals.
Which of the following lists of features exemplifies the domain Archaea?
A. Multicellular, varying branched lipids in their cell membrane, no nuclear envelope, and contain some introns B. Unicellular, unbranched phospholipids in their cell membrane, no nuclear envelope, and contain some introns C. Unicellular, varying branched lipids in their cell membrane, nuclear envelope, and contain some introns D. Unicellular, varying branched lipids in their cell membrane, no nuclear envelope, and contain some introns
Which of the following is noncellular?
A) fungi B) viruses C) protozoa D) algae