A stretch receptor is classified as a
a. chemoreceptor.
b. mechanoreceptor.
c. photoreceptor.
d. thermoreceptor.
e. all of these.
B
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What is the process by which light energy is converted into the stored chemical energy of organic molecules?
a. diffusion b. endocytosis c. respiration d. fermentation e. photosynthesis
Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity. It normally binds to receptors in the brain and inhibits appetite. Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight. Interestingly, however, many overweight people have high levels of leptin in their bloodstream. Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite?
A. The form of leptin released by obese people may lack protein kinase activity. B. Paracrine signaling may be disrupted in obese people with high levels of leptin. C. Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity. D. In obese people with high levels of leptin, the leptin is a nonfunctional second messenger.
In the following sequence of DNA, the italicized base has been mutated. What type of mutation is this?
5' - G A T C T C C G A A T T - 3' original strand 5' - G A T C T C C C A A T T - 3' mutated strand A. Transition B. Transversion C. Neither
Which statement about bryophytes is NOT true?
a. The sporophyte is haploid. b. The sporangium produces spores. c. The sporophyte is attached to the gametophyte. d. Meiosis precedes spore formation. e. Bryophytes require water for sexual reproduction.