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. Paracrine signaling may be disrupted in obese people with high levels of leptin.
B. Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity.
C. The form of leptin released by obese people may lack protein kinase activity.
D. In obese people with high levels of leptin, the leptin is a non-functional second messenger.
B. Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity.
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Which of the following statements about differentiated cells is not correct?
A. Transfer of a nucleus from a fully differentiated cell into an unfertilized egg with no nucleus can support the development of an entire organism. B. Cells become differentiated because of changes in nuclear gene expression. C. Cells become differentiated because genes that are not being expressed are deleted. D. Differentiated cells contain a complete genome. E. Mammals have been cloned from completely differentiated cells.
In which of the stages below are the chromosomes present as attached sister chromatids? I. metaphase II. telophase III. prophase IV. anaphase
a. III and IV b. I, III, and IV c. I and III d. I, II, and III e. I, II, III, and IV
Which of these cranial bones separates the cranial cavity from the nasal cavity and provides the olfactory nerves with access to the brain?
A) temporal B) foramen magnum C) sphenoid D) ethmoid
What happens to each daughter cell at the conclusion of mitosis?
a. It has DNA identical to the parent cell. b. It has twice the cytoplasm and the same amount of DNA as the parent cell. c. It has twice the amount of DNA and half the cytoplasm of the parent cell. d. It has half the DNA and half the cytoplasm found in the parent cell.