Which of the following bones is NOT a part of the human skull?
a. iliac
b. frontal
c. ethmoid
d. occipital
e. temporal
A
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Osmosis involves
a. the movement of a solvent, like water. b. differences in solute concentrations. c. movement from hypotonic to hypertonic solutions. d. all of these except e. e. all of these except c and d.
Which vertebrate is a fish, has a cartilaginous skeleton, no jaws, and a tooth-covered tongue?
a. shark b. lamprey c. coelacanth d. goldfish e. lungfish
The ?-helix and ?-pleated sheet are examples of which level of protein structure?
A. primary B. secondary C. tertiary D. quaternary
The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells
When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true? (a) Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. (b) Glial cells do not have a receptor for QGF. (c) QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. (d) Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF.