All amino acids, such as the four represented in the figure, contain __________.

Macromolecules that are used by most organisms to store hereditary information are called:

A. proteins. B. transfer RNA molecules. C. ribosomal RNA molecules. D. DNA molecules. E. messenger RNA molecules.

Which of the following is the best explanation for the fact that most transduction pathways have multiple steps?

A) Most of the steps were already in place because they are steps in other pathways. B) Multiple steps in a pathway require the least amount of ATP. C) Multiple steps provide for greater possible amplification of a signal. D) Each individual step can remove excess phosphate groups from the cytoplasm. E) Each step can be activated by several G proteins simultaneously

In their famous experiment, which of the following would Meselson and Stahl have observed after one cycle of replication in 14N medium if DNA replication was conservative?

A) DNA molecules containing one strand of 15N-DNA and one strand of 14N-DNA B) DNA molecules containing two 15N-DNA strands only C) DNA molecules containing two 14N-DNA strands only D) An equal number of DNA molecules containing two 15N-DNA strands and DNA molecules containing two 14N-DNA strands. E) A mix of DNA molecules corresponding to A and B.

Above 8,000 feet, the body's response to low oxygen concentration in the atmosphere is

a. hyperventilation. b. reduced breathing rate. c. slowed heart rate. d. decreased production of red blood cells. e. "the bends."