When you hold your breath, which of the following blood gas changes leads initially to the urge to breathe again?
A) rising oxygen concentration
B) rising carbon dioxide concentration
C) falling oxygen concentration
D) falling carbon dioxide concentration
Answer: B
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Which of the following is the smallest unit in terms of size?
A. quadriceps B. myofibril C. muscle fiber D. sarcomere E. myofilaments
Character changes in molecular sequences are generated by
a. insertions. b. deletions. c. substitutions. d. base pairing. e. insertions, deletions, and substitutions.
The obvious advantage of the lactose operon is that it
a. allows bacteria to survive in the presence of lactose. b. eliminates the need for lactose-metabolizing enzymes when lactose is not present. c. enables bacteria to make lactose only in the presence of the proper enzymes. d. negates the need for milk in the diet of adult humans. e. enables glucose to substitute for lactose in the diet of lactose intolerant persons.
Water "beads up" on synthetic fabric such as polyester but binds to cotton. What is the most likely explanation for this?
A) Polyester is not a naturally occurring substance, whereas cotton is a naturally occurring substance. B) Polyester is more flexible than cotton. C) Polyester fibers are thinner than cotton fibers. D) Polyester is nonpolar, whereas cotton is polar.