Cell Communication
1. Which of the following pairs is not correctly matched?
a. Porin-ionophore
b. Plasmodesmata-gap junction
c. Plant cell wall-bacterial cell wall
d. Tight junction-middle lamella
e. None of the above
2. Cocaine inhibits the reabsorption of the neurotransmitter norepinephrine. What effect does this have on a nerve cell?
a. Prevent depolarization
b. Causes polarization
c. Causes hyperpolarization
d. Causes action potentials
e. None of the above
3. A cancer-causing gene makes G protein permanently bind to GTP, this results in:
a. Continual production of cAMP
b. Continual production of GDP
c. Inhibition of cGMP production
d. Inhibition of adenylyl cyclase
e. None of the above
4. The steps for an action potential are listed below. What is the first step?
a. Depolarization
b. K+ channels open
c. Na+ channels open
d. Polarization
e. Repolarization
5. The steps in G protein-mediated signal transduction are listed below. What is the third step?
a. G protein binds GDP
b. Hormone binds to its receptor
c. G binds to GTP
d. G activates adenylyl cyclase
e. GTP -> GDP
6. Canine kidney cell cultures develop invasive cancer cell characteristics when they are treated with antibodies against E-cadherin. This indicates that the rode of cadherin is:
a. Signal transduction
b. Cell communication
c. Initiating an action potential
d. Cell migration
e. None of the above
7. _E. coli_ O157:H7 bacteria produce an enterotoxin that allows Gs to bind to GTP but inhibits the hydrolysis of GTP. The effect is:
a. cAMP cannot be formed
b. Adenylyl cyclase will continuously produce cAMP
c. The cell will not respond to a signal
d. Second messengers will not be formed
e. None of the above
8. The hormone glucagon stimulates the breakdown of stored glycogen in liver and muscle cells by the following enzymes. Which is the first enzyme that must be activated?
a. Protein kinase A
b. Phosphorylase kinase
c. Glycogen phosphorylase
d. Protein phosphatase
e. Protein phosphatase inhibitor
9. Cancerous liver cells can be restored to their normal growth by inserting the gene for E-cadherin. This indicates that cadherin is involved in:
a. Formation of the extracellular matrix
b. Opening voltage-gated channels
c. Activation of cAMP
d. Cell migration
e. None of the above
10. Developing frog embryos treated with anti-fibronectin antibodies:
a. Develop normally
b. Stop cell division
c. Have abnormal cell migration
d. Don't exhibit action potentials
e. None of the above
11. During the day, plant guard cells become turgid which opens the stomate between adjacent guard cells. The following steps are required for stomatal opening. Which is the fifth step?
a. H+ pumped out by ATPase-hyperpolarization
b. K+ influx-repolarization
c. Light-signal
d. Water enters-turgidity
e. K+ channels open-voltage gated channel
12. The nerve cell body contains all of the following except:
a. Ribosomes
b. ER
c. Golgi complex
d. Mitochondria
e. None of the above
13. In an unstimulated nerve:
a. The inside is negatively charged compared to the outside
b. The outside is negatively charged compared to the inside
c. The intracellular and extracellular charges are equal
d. It depends on the nerve
e. None of the above
14. Which of the following conditions occurs in depolarization?
a. Na+ channels closed; Cl- channels open
b. Na+ channels closed; K+ channels closed
c. Na+ channels closed; K+ channels opened
d. Na+ channels opened; K+ channels closed
e. None of the above
15. Release of acetylcholine causes:
a. Na+ efflux
b. Na+ influx
c. K+ efflux
d. K+ influx
e. None of the above