Campbell Biology Chapter 11

In yeast signal transduction, a yeast cell releases a mating factor which _____.

C) binds to receptors on the membranes of other types of yeast cells

Which of the following statements about quorum sensing is FALSE? Quorum sensing _____

A) is cell-cell communication in eukaryotes

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

B) aggregation of bacteria that can cause cavities

Which of the following is a type of local signaling in which a cell secretes a signal molecule that affects neighboring cells?

C) paracrine signaling

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must _____.

D) have receptors that recognize and bind the hormone molecule

In which of the following ways do plant hormones differ from hormones in animals?

A) Plant hormones most often travel in air as a gas.

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

C) signal molecule

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine’s effect on liver cells?

B) Glycogen breakdown was observed only when epinephrine was administered to intact cells.

A G-protein receptor with GTP bound to it ____

A) is in its active state

Testosterone functions inside a cell by _____.

B) binding with a receptor protein that enters the nucleus and activates specific genes

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. For this to happen there must be direct communication between the extracellular matrix and the developing cells. Which kind of transmembrane protein would most likely be involved in this kind of induction?

A) integrins

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

D) receptor tyrosine kinases

A drug designed to inhibit the response of cells to testosterone would most likely result in _____.

B) a decrease in transcriptional activity of certain genes

Lipid-soluble signaling 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

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

A) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane

Which of the following is true of steroid receptors?

B) The receptor may be inside the nucleus of a target cell.

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. HER2 is sometimes excessive in cancer cells. This information can now be utilized in breast cancer treatment if which of the following is true?

B) if the patient’s cancer cells have excessive levels of HER2

Which of the following would be inhibited by a drug that specifically blocks the addition of phosphate groups to proteins?

D) receptor tyrosine kinase activity

Which of the following is characteristic of a steroid hormone action?

C) internal receptor binding

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is not a problem for steroids because _____.

C) steroid hormones are lipid soluble, so they can readily diffuse through the lipid bilayer of the cell membrane

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

A) a lipid-soluble signal

What does it mean to say that a signal is transduced?

B) The physical form of the signal changes from one form to another.

Protein phosphorylation is commonly involved with all of the following EXCEPT _____.

C) activation of G protein-coupled receptors

In general, a signal transmitted via phosphorylation of a series of proteins _____.

A) results in a conformational change to each protein

Which of the following is the best explanation for the inability of a specific animal cell to reduce the Ca2+ concentration in its cytosol compared with the extracellular fluid?

C) insufficient ATP levels in the cytoso

The toxin of Vibrio cholerae causes profuse diarrhea because it _____

A) modifies a G protein involved in regulating salt and water secretion

Which of the following would most likely be an immediate result of a growth factor binding to its receptor?

A) protein kinase activity

Adenylyl cyclase has the opposite effect of which of the following?

C) phosphodiesterase

Caffeine is an inhibitor of phosphodiesterase. Therefore, the cells of a person who has recently consumed coffee would have increased levels of _____.

B) cAMP

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

C) phospholipase C

Which of the following statements is true of signal molecules?

D) Protein kinase A activation is one possible result of signal molecules binding to G protein-coupled receptors.

Which of the following is a correct association?

C) GTPase activity and hydrolysis of GTP to GDP

Protein kinase is an enzyme that _____

C) activates or inactivates other proteins by adding a phosphate group to them

Viagra causes dilation of blood vessels and increased blood flow to the penis, facilitating erection. Viagra acts by inhibiting _____.

A) the hydrolysis of cGMP to GMP

Which of the following amino acids are most frequently phosphorylated by protein kinases in the cytoplasm during signal transduction?

C) serine and threonine

In signal transduction, phosphatases _____.

D) inactivate protein kinases and turn off the signal transduction

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound _____.

C) to block G protein activity in liver cells

If a pharmaceutical company wished to design a drug to maintain low blood sugar levels, one approach might be to design a compound _____.

D) that increases phosphodiesterase activity

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is _____.

A) cAMP

Sutherland discovered that the signaling molecule epinephrine _____.

D) elevates cytosolic concentrations of cyclic AMP

Which of the following is true during a typical cAMP-type signal transduction event?

D) Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Put the steps of the process of signal transduction in the order they occur:
1. A conformational change in the signal-receptor complex activates an enzyme.
2. Protein kinases are activated.
3. A signal molecule binds to a receptor.
4. Target proteins are phosphorylated.
5. Second messenger molecules are released.

C) 3, 1, 5, 2, 4

Transcription factors _____.

C) control gene expression

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

D) Estrogen binds to specific receptors inside many kinds of cells, each with different responses

Scaffolding proteins are _____.

B) large molecules to which several relay proteins attach to facilitate cascade effects

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

C) amplify the original signal many times

GTPase activity is important in the regulation of signal transduction because it _____.

C) hydrolyzes GTP to GDP, thus shutting down the pathway

Why has C. elegans proven to be a useful model for understanding apoptosis?

B) The nematode undergoes a fixed and easy-to-visualize number of apoptotic events during its normal development.

Which of the following describes the events of apoptosis?

C) The cell’s DNA and organelles become fragmented, the cell shrinks and forms blebs, and the cell’s parts are packaged in vesicles that are digested by specialized cells.

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

B) a form of cancer in which there is insufficient apoptosis

Why is apoptosis potentially threatening to the healthy "neighbors" of a dying cell?

B) Lysosomal enzymes exiting the dying cell would damage surrounding cells.

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

A) It prevents the caspase activity of ced-3 and ced-4.

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following, if found in cells or organisms as they age, would provide evidence that this is related to cell signaling?

A) Growth factor ligands do not bind as efficiently to receptors.

Apoptosis involves all but which of the following?

C) lysis of the cell

Which of the following poses the best evidence that cell-signaling pathways evolved early in the history of life?

C) Signal transduction molecules identified in distantly related organisms are similar.

Cells that are infected, damaged, or have reached the end of their functional life span often undergo "programmed cell death." This controlled cell suicide is called apoptosis. Select the appropriate description of this event on a cell’s life cycle.

C) During apoptosis, cellular agents chop up the DNA and fragment the organelles and other cytoplasmic components of a cell.