Which of the following statements is true of signal molecules?
A) When signal molecules first bind to receptor tyrosine kinases, the receptors phosphorylate a number of nearby molecules.
B) In response to some G protein-mediated signals, a special type of lipid molecule associated with the plasma membrane is cleaved to form IP3 and calcium.
C) In most cases, signal molecules interact with the cell at the plasma membrane, enter the cell, and eventually enter the nucleus.
D) Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.
D
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Type 2 diabetes is caused by:
a. too much insulin in the blood. b. too little insulin in the blood. c. too much glucagon in the blood. d. too little glucagon in the blood. e. receptors being insensitive to insulin.
Experimental plants that were sent up in space shuttle missions did not exhibit all of their normal tropisms. Which of the following responses would you most expect to be lacking from these plants?
A) gravitropism B) photoperiod C) thigmotropism D) phototropism
What do polysaccharides, such as cellulose; nucleic acids, such as DNA; and proteins, such as keratin, have in common?
A) They are all amino acids. B) They are all nonpolar. C) They are all built of chemically linked monomers. D) They are all lipids. E) They are all carbohydrates.
An X-ray revealed that Josh's lungs were filled with fluid. What is the proper diagnosis of Josh's illness?
A. pneumonia B. pulmonary fibrosis C. asthma D. bronchitis E. emphysema