Campbell Biology

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

Chapter 11

Cell Communication - all with Video Answers

Educators

Chapter Questions

Problem 1

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?
a. intracellular receptor
b. G protein-coupled receptor
c. phosphorylated receptor tyrosine kinase dimer
d. ligand-gated ion channel

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 2

The activation of receptor tyrosine kinases is characterized by
a. dimerization and phosphorylation.
b. dimerization and IP $_{3}$ binding.
c. a phosphorylation cascade.
d. GTP hydrolysis.

Archit Kothari

Numerade Educator

Problem 3

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because
a. only target cells retain the appropriate DNA segments.
b. intracellular receptors are present only in target cells.
c. only target cells have enzymes that break down aldosterone.
d. only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes on.

Archit Kothari

Numerade Educator

Problem 4

Consider this pathway: epinephrine $\rightarrow$ G protein-coupled receptor $\rightarrow$ G protein $\rightarrow$ adenylyl cyclase $\rightarrow$ cAMP. Identify the second messenger.
a. cAMP
c. GTP
b. G protein
d. adenylyl cyclase

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 5

Apoptosis involves all but which of the following?
a. fragmentation of the DNA
b. cell-signaling pathways
c. lysis of the cell
d. digestion of cellular contents by scavenger cells

Aditya Sood

Numerade Educator

Problem 6

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?
a. Enzymaticactivity was proportional to the amount of calcium added to a cell-free extract.
b. Receptor studies indicated that epinephrine was a ligand.
c. Glycogen breakdown was observed only when epinephrine was administered to intact cells.
d. Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined.

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 7

Protein phosphorylation is commonly involved with all of the following except
a. activation of receptor tyrosine kinases.
b. activation of protein kinase molecules.
c. activation of G protein-coupled receptors.
d. regulation of transcription by signaling molecules.

Archit Kothari

Numerade Educator

Problem 8

Draw the following apoptotic pathway, which operates in human immune cells. A death signal is received when a molecule called Fas binds its cell-surface receptor. The binding of many Fas molecules to receptors causes receptor clustering. The intracellular regions of the receptors, when together, bind proteins called adaptor proteins. These in turn bind to inactive molecules of caspase- $8,$ which become activated and then activate caspase-3. Once activated, caspase-3 initiates apoptosis.

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 9

What evolutionary mechanisms might account for the origin and persistence of cell-to-cell signaling systems in prokaryotes?

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 10

Epinephrine initiates a signal transduction pathway that produces cyclic AMP (cAMP) and leads to the breakdown of glycogen to glucose, a major energy source for cells. But glycogen breakdown is only part of the fight-or-flight response that epinephrine brings about; the overall effect on the body includes an increase in heart rate and alertness, as well as a burst of energy. Given that caffeine blocks the activity of cAMP phosphodiesterase, propose a mechanism by which caffeine ingestion leads to heightened alertness and sleeplessness.

Micháel Riley Ii

Micháel Riley Ii

Numerade Educator

Problem 11

The aging process is thought to be initiated at the cellular level. Among the changes that can occur after a certain number of cell divisions is the loss of a cell's ability to respond to growth factors and other signals. Much research into aging is aimed at understanding such losses, with the ultimate goal of extending the human life span. Not everyone, however, agrees that this is a desirable goal. If life expectancy were greatly increased, what might be the social and ecological consequences?

Eric Goldman

Numerade Educator

Problem 12

The properties of life emerge at the biological level of the cell. The highly regulated process of apoptosis is not simply the destruction of a cell; it is also an emergent property. Write a short essay (about $100-150$ words) that briefly explains the role of apoptosis in the development and proper functioning. of an animal, and describe how this form of programmed cell death is a process that emerges from the orderly integration of signaling pathways.

Leah Lampen

Numerade Educator

Problem 13

There are five basic tastes - sour, salty, sweet, bitter, and "umami." Salt is detected when the concentration of salt outside of a taste bud cell is higher than that inside of it, and ion channels allow the passive leakage of $\mathrm{Na}^{+}$ into the cell. The resulting change in membrane potential (see Concept 7.4 ) sends the "salty" signal to the brain. Umami is a savory taste generated by glutamate (glutamic acid, found in monosodium glutamate, or MSG), which is used as a flavor enhancer in foods such as taco-flavored tortilla chips. The glutamate receptor is a GPCR, which, when bound, initiates a signaling pathway that ends with a cellular response, perceived by you as "taste." If you eat a regular potato chip and then rinse your mouth, you will no longer taste salt. But if you eat a flavored tortilla chip and then rinse, the taste persists. (Try it!) Propose a possible explanation for this difference.

Joshlyn Resek

Numerade Educator