Biology 111B
Study Questions 7

CELL COMMUNICATION

 

1. Define or describe the following:

ligand -

receptor protein -

relay molecule -

signal transduction -

protein kinase -

2. What determines which signal molecules a cell will respond to?

 

3. What is the typical mechanism of response to a steroid hormone signal?

 

4. How can the information that a signal has been received be passed from a membrane-bound receptor to an interior target cell?

 

5. How does the reception of a single signal molecule get amplified to cause a response in millions of target molecules?

 

6. Protein phosphorylation is commonly involved with which of the following? (choose all that apply)

a. regulation of DNA expression by lipid signal molecules

b. regulation of DNA expression by non-lipid signal molecules

c. activation of ligand-gated ion channels

d. activation of protein kinase molecules

 

7. Amplification of a chemical signal would likely occur when… (choose all that apply)

a. a receptor in the plasma membrane activates relay molecules while a signal is bound to it

b. a relay molecule activates one protein kinase molecule before being deactivated

c. the enzymes that activate and deactivate protein kinase "1" are in equal concentration

d. a single ligand causes many transport channels to open in the ER

 

8. Lipid-soluble signal molecules, such as testosterone, cross the plasma membranes of all cells but affect only their target cells because… (choose all correct answers)

a. only target cells have the appropriate DNA segments

b. intracellular receptors are present only in target cells

c. only target cells have the relay proteins required to transduce the signal

d. membrane receptors are found only in target cells

 

9. Signal-transduction pathways benefit cells for which of the following reasons?

a. they help cells respond to signal molecules that are too large or too polar to cross the cell membrane

b. they enable different cells to respond appropriately to the same signal

c. variations in the signal-transduction pathways can enhance response specificity

d. they can amplify a signal

 

10. Very rarely, a genetic male is physically female. This is known as "testosterone insensitivity" because testosterone is produced but it has no effect. Describe a simple mechanism that would cause this condition based on the mechanism of testosterone action.

 

11. Cholera is an often-fatal disease with symptoms of severe diarrhea and salt loss. It is caused by a bacterium, Vibrio cholerae, which colonizes the small intestine. This bacterium secretes a toxin that interferes with the ability of a relay molecule to be "turned off." The relay molecule normally activates membrane channels that actively transport salts out of the small intestine epidermal cells into the interior of the small intestine. Why would this toxin cause the symptoms described?