Self Quiz Chapter 11: Cell Communication

1) Cholera is a widespread, serious disease of humans. Scientists have been studying ways to control the disease. Effective controls would require research on
A) mating factors in the disease-causing bacteria.
B) the effect of the cholera toxin on G-pathway proteins.
C) the structure and function of the bacteria's tyrosine-kinase receptors.
D) the effect of the cholera toxin on synaptic signaling in humans.

2) An animal is born without a fully functional adrenal gland. Of the following, the most likely consequence would be
A) loss of ability to transmit signals through a synapse.
B) poor production of insulin.
C) poor mobilization of energy reserves during mental stress.
D) overproduction of blood glucose.
E) inability of the cells to divide in the gland.

3) Chemical signal
A) systems are absent in bacteria, but are plentiful in yeast.
B) pathways operate in animals, but few operate in plants.
C) systems usually involve detection by binding to a target cell surface protein.
D) pathways in nature involve the release of hormones into the blood.

4) In yeast (Saccharomyces cerevisiae), the two sexes are called
A) S plus and S minus.
B) b and beta.
C) a and alpha.
D) a and b.
E) male and female.

5) In the yeast signal-transduction pathway, after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells,
A) the cell membranes fall apart, releasing the mating factors that lead to new yeast cells.
B) the cells then produce the a-factor and the alpha-factor.
C) one cell nucleus binds the mating factors and produces a new nucleus in the opposite cell.
D) binding induces changes in the cells that leads to cell fusion.

6) Which of the following is true of calmodulin?
A) It mediates many calcium-regulated processes in cells.
B) It is a Ca2+ binding protein.
C) It is present in high levels in eukaryotic cells.
D) All of the above .
E) None of the above .

7) Which of the following is true of the mating signal-transduction pathway in yeast?
A) The molecular details of the pathway in yeast and in animals are very different.
B) Mating type a secretes a signal called a-factor.
C) Scientists think the pathway evolved long after multicellular creatures appeared on Earth.
D) The pathway carries an electrical signal between mating cell types.

8) In general, a signal transmitted via phosphorylation of a series of proteins
A) cannot occur in yeasts because they lack protein phosphatases.
B) brings a conformational change to each protein.
C) requires binding of a hormone to a cytosol receptor.
D) always results in enzyme activation inside the target cell.
E) allows target cells to change their shape and therefore their activity.

9) Transcription factors
A) regulate the synthesis of DNA in response to a signal.
B) initiate the epinephrine response in animal cells.
C) transcribe ATP into cAMP.
D) None of the above is true of transcription factors.

10) A small molecule that specifically binds to a larger one
A) is a polymer.
B) is a ligand.
C) is called a signal transducer.
D) seldom is involved in hormone signaling.
E) usually terminates a signal reception.

11) Which of the following signal systems does NOT use G-protein-linked receptors?
A) epinephrine
B) yeast mating factors
C) neurotransmitters
D) None of these use G-protein-linked receptors.
E) All of these use G-protein-linked receptors.

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

13) Paracrine signaling
A) involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
B) occurs only in paracrine yeast cells.
C) has been found in plants but not animals.
D) involves mating factors attaching to target cells and causing production of new paracrine cells.
E) requires nerve cells to release a neurotransmitter into synapse.

14) The ability of a single ligand binding to a receptor protein to trigger several pathways
A) does not occur in animals, but is common in bacteria.
B) is characteristic of the synaptic signal system.
C) is common to all plasma membrane receptor proteins.
D) is unique to the yeast mating system.
E) is a key difference between tyrosine-kinase and G-protein-linked receptor systems.

15) G proteins and G-protein receptors
A) are found only in animal cells.
B) are not widespread in nature and were unimportant in the evolution of eukaryotes.
C) are thought to have evolved very early, possibly as sensory receptors in ancient bacteria.
D) are found only in bacterial cells.
E) probably evolved from an adaptation of the Krebs cycle.