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A signal molecule is also known as a(n) _____. (Activity: Overview of Cell Signaling)
A. ligand
2. When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A2. Thromboxane A2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example thromboxane A2 is acting as a(n) _____. (Concept 11.1)

local regulator
3. Early work on signal transduction and glycogen depolymerization by Sutherland indicated that _____. (Concept 11.1)

the signal molecule did not interact directly with the cytosolic enzyme, but required an intact plasma membrane before the enzyme could be activated

4. Certain yeast cells secrete a molecule called the α factor. The purpose of this molecule is to
stimulate an α yeast cell to grow toward the α cell
6. Testosterone and estrogen are lipid-soluble signal molecules that cross the plasma membrane by simple diffusion. If these molecules can enter all cells, why do only specific cells respond to their presence? (Concept 11.2)

Nontarget cells lack the intracellular receptors that, when activated by the signal molecule, can interact with genes in the cell's nucleus.

7. Steroid hormones can enter a cell by simple diffusion. Therefore steroids _____.
do not initiate cell signaling by interacting with a receptor in the plasma membrane.

8. A small molecule that specifically binds to a larger molecule is called a(n) _____. The
9. Receptors for signal molecules _____. (Concept 11.2)

can be found as part of the plasma membrane or found within the cytoplasm

10. Testosterone does not affect all cells of the body because _____. (Concept 11.2)

not all cells have cytoplasmic receptors for testosterone
11. G-protein-linked receptors _____; whereas tyrosine-kinase receptors _____.
are not enzymes ... have enzymatic function
12. Which of the following is activated when the binding of single molecules causes it to form a dimer? (Concept 11.2)

tyrosine-kinase receptors
13. The binding of a signal molecule to a ligand-gated ion channel _____. (Concept 11.2)

affects the membrane potential
14. Nitric oxide is unusual among animal signal molecules in that it _____. (Concept 11.2)

is a gas
15. A G protein is active when _____. (Concept 11.2)

GTP is bound to it

16. Botulism toxin acts by interfering with _____ function. (Concept 11.2)

17. If a modified form of GTP that cannot be enzymatically converted to GDP were added to a culture of cells, the likely result would be _____. (Concept 11.2)

that the activated G proteins would remain locked in the "on" position, transmitting signal even in the absence of signaling molecule

18. What event would activate a G protein? (Concept 11.2)

replacement of GDP with GTP
19. Cholera develops when the bacterial toxin _____. (Concept 11.2)

prevents G-protein inactivation, which leads to the continuous production of cAMP

20. The cellular response of a signal pathway that terminates at a transcription factor would be _____. (Concept 11.2)

the synthesis of mRNA
21. What did Sutherland discover about glycogen metabolism in liver cells? (Concept 11.3)

The hormone epinephrine binds to a specific receptor on the plasma membrane of the liver cell.
22. The general name for an enzyme that transfers phosphate groups from ATP to a protein is
protein kinase

23. Phosphorylation _____. (Concept 11.3)

can either activate or inactivate a protein

24. The source of phosphate for a phosphorylation cascade is _____. (Concept 11.3)

25. Second messengers tend to be both water-soluble and small. This accounts for their ability to _____. (Concept 11.3)

rapidly move throughout the cell by diffusion
26. cAMP usually directly activates _____. (Concept 11.3)

protein kinase A

27. In a typical cell, calcium ions _____. (Concept 11.3)

are often concentrated within the endoplasmic reticulum
28. During the transduction of a signal, one molecule or ion may be closely associated with the activity of another. Select the pair that is correctly combined. (Concept 11.3)

all of the above
29. A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP _____ and Ca2+ _____. (Concept 11.3)

is synthesized by an enzyme in response to a signal ... released from intracellular stores

30. IP3 (inositol trisphosphate) is produced as a result of _____. (Concept 11.3)

the cleavage of PIP2
31. IP3 (inositol trisphosphate) acts by _____. (Concept 11.3)

opening Ca2+ channels

32. Which of the following is not a potential source of Ca2+ for the cytosol? (Concept 11.3)


33. In eukaryotic cells, which one of the following is a second messenger that is produced as a response to an external signal such as a hormone? (Concept 11.3)

cyclic AMP
34. Which of the following sequences is correct? (Concept 11.3)

binding of a growth factor to its receptor ® phosphorylation cascade ® activation of transcription factor ® transcription

35. In the inherited disorder Wiskott-Aldrich syndrome _____. (Concept 11.4)

a multifunctional relay protein involved with the proliferation of immune cells is defective

36. In liver cells, epinephrine stimulates the breakdown of glycogen. As the signal-transduction pathway progresses, _____. (Concept 11.4)

the signal is amplified
37. Cells of the gastrointestinal (GI) tract and cells of the heart respond differently to epinephrine because _____. (Concept 11.4)

there are differences in the proteins found in the two types of cells
1. Amplification of a chemical signal occurs when
a. a receptor in the plasma membrane activates several G– protein molecules while a signal molecule is

2. Which of the following provides the best evidence that cell–signaling pathways evolved early in the history of life?

c. Signal transduction molecules found in distantly related organisms are similar.

5. Binding of a signal molecule to which type of receptor leads directly to a change in the distribution of anions and/or cations on opposite sides of the membrane?

d. ligand–gated ion channel

6. Protein phosphorylation is commonly involved with all of the following except

c. activation of G–protein–linked receptors.

7. Signal transduction pathways benefit cells for all of the following reasons except

c. they help cells use up phosphate generated by ATP breakdown.

8. Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because

c. they amplify the original signal manyfold.

9. The activation of receptor tyrosine kinases is always characterized by

a. dimerization and phosphorylation.

10. Lipid–soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

b. intracellular receptors are present only in target cells.

Sister chromatids separate during _____. (Concept 12.2)
  1. anaphase
The function of the cell cycle is to produce daughter cells that _____. (Concept 12.1)
A. are genetically identical to the parent cell (assuming no mutation has occurred)
You would know a dividing cell was a plant cell rather than an animal cell if you saw that _____. (Concept 12.2)
A. it had formed a cell plate
Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-forming on either side of the cell plate. This cell is most likely
B. a plant cell in the process of cytokinesi
The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____. (Concept 12.2)
B. anaphase
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