Which of the following is the best explanation for the inability of an animal cell to reduce the

34.Which of the following is the best explanation for the inability of an animal cell to reduce the   concentration in its cytosol compared with the extracellular fluid?
a.blockage of the synaptic signal
b.loss of transcription factors
c.insufficient ATP levels in the cytoplasm
d.low oxygen concentration around the cell
e.low levels of protein kinase in the cell


____35.The general name for an enzyme that transfers phosphate groups from ATP to a protein is
a.phosphorylase.
b.phosphatase.
c.protein kinase.
d.ATPase.
e.protease.


____36.Which of the following is not true of cell communication systems?
a.Cell signaling was an early event in the evolution of life.
b.Communicating cells may be far apart or close together.
c.Most signal receptors are bound to the outer membrane of the nuclear envelope.
d.Protein phosphorylation is a major mechanism of signal transduction.
e.In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of RNA.


____37.The toxin of Vibrio cholerae causes profuse diarrhea because it
a.modifies a G protein involved in regulating salt and water secretion.
b.decreases the cytosolic concentration of calcium ions, making the cells hypotonic to the intestinal cells.
c.binds with adenylyl cyclase and triggers the formation of cAMP.
d.signals inositol trisphosphate to become a second messenger for the release of calcium.
e.modifies calmodulin and activates a cascade of protein kinases.


____38.Which of the following is not part of the phosphorylation cascade model?
a.A signal molecule binds to a membrane receptor protein.
b.Protein kinase is activated.
c.GTP donates a phosphate group to an inactive protein kinase.
d.A specific protein is activated via phosphorylation.
e.A cellular response is initiated.


____39.In a typical cell, calcium ions are
a.far more abundant in the blood and other extracellular fluid than in the cytoplasm.
b.rapidly released from the endoplasmic reticulum in response to G-protein-mediated signals.
c.often concentrated within the endoplasmic reticulum.
d.A and B only
e.A, B, and C


____40.Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?
a.G-protein-linked receptor signaling
b.ligand-gated ion channel signaling
c.adenylyl cyclase activity
d.phosphatase activity
e.receptor tyrosine kinase activity