Bacteria in biofilms
A) are composed of only a single species.
B) are easily treated and removed.
C) form on teeth, medical devices and in the middle ear.
D) behave the same way as planktonic, or single-living bacteria.
Ans: C) form on teeth, medical devices and in the middle ear.
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Photoreceptors are found in the
(a) lens. (b) ciliary body. (c) iris. (d) retina.
During the light-dependent reactions, NADPH ____.
A. is an enzyme B. is the oxidized form of NADP+ C. accepts hydrogen and electrons from water D. accepts hydrogen and electrons from carbohydrates E. obtains energy from ATP
Cooksonia is a genus of very early tracheophyte plants. Unlike modern tracheophytes, they only grew to a few centimeters in height. What feature provides the best explanation for their diminutive size?
A. Cooksonia species were not autotrophic. B. They consisted of only photosynthetic stems, not roots or leaves. C. They completely lacked vascular tissues. D. They did not have stomata.
Which of the following statements is true?
(a) Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior. (b) To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. (c) A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. (d) Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.