Valves, which are found ________, maintain the unidirectional movement of blood, thereby facilitating the return of blood to the heart.
A) only in central veins
B) in all venules
C) only in peripheral veins
D) only in arteries
E) in all veins
Answer: C) only in peripheral veins
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An amino acid most likely to be found in a reverse turn is:
A. glycine. B. valine. C leucine. D. isoleucine. E. methionine.
Which one of the following characteristics of steroid hormones is not shared by nonsteroid hormones?
A. Hormones activate the transcription of particular genes in response to system requirements. B. Hormones bind to hormone receptors. C. Responsiveness to hormones can be cell- or tissue-specific. D. The hormone crosses the plasma membrane.
Your friend discovered a new multicellular organism living under the polar ice caps, and brought it back to the laboratory, where it seems to be growing well
Your friend is particularly interested in the proteins that allow this organism to survive in extreme cold. Because he is interested in proteins and because he has learned that most of the human genome does not code for exons, he is considering sequencing expressed sequence tags from this organism. What do you think the pitfalls of this approach might be? Explain.
Ecdysis is
A. development of the ectoderm layer in the gastrula. B. the feeding tentacles of the Ecdysozoa. C. molting of the exoskeleton. D. development of the epidermis from the ectoderm. E. disintegration of the ectoderm.