A.P. Bio. Chapt. 11

A drug designed to inhibit the response of cells to testosterone would almost certainly result in what?

A decrease in transcriptional activity in certain genes.

G proteins and G-protein-linked receptors

Are thought to have evolved very early, because of their similar structure and function in a wide variety of modern organisms.

What explains the increased concentration of Ca⁺⁺ in the ER?

Calcium ions are actively imported from the cytoplasm into the ER.

Membrane receptors that attach phosphates to specific animo acids in proteins are

Called receptor tyrosine-kinases.

The activation of receptor tyrosine kinases is characterized by

Dimerization and phosphorylation.

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?

Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding.

Which of the following is a likely explanation of why natural selection favored the evolution of signals for sexual reproduction?

Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.

Up to 60% of all medicines used today exert their effects by influencing what structues in the cell membrane?

G proteins.

Which of the following is a correct association?

GTPase activity & hydrolysis of GTP to GDP

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

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

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 would provide evidence that this is related to cell signaling?

Growth factor ligands do not bind as efficiently to receptors.

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

If the patient's cancer cells have detectable HER2.

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

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

A small molecule that specifically binds to another molecule, usually a larger one

Is called a ligand.

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

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

What would be true for the signaling systen in an animal cell that lacks the ability to produce GTP?

It wouldn't be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

What is a description of the events of apoptosis?

Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.

Which of the following describes the events of apoptosis?

Its DNA and organelles are fragmented, the cell shrinks and forms blebs, and the cell self-digests.

Humans have receptors for two kinds of beta adrenergic compounds such as catecholamines to control cardiac muscle contractions. Some are beta 1 receptors that promote increased heart rate. Other drugs, called beta blockers, slow heart rate. Smooth muscle cells, however, have beta 2 receptors, which mediate muscle relaxation. Blockers of these effects are sometimes used to treat asthma.

Just because a drug acts on one type of receptor does not mean that it will act on another type.

What are scaffolding proteins?

Large molecules to which several relay proteins attach to facilitate cascade effects.

Binding of a signaling molecule to which type of receptor leads directly to a change in distribution of ions on opposite sides of the membrane?

Ligand-gated ion channel.

What isn't involved in apoptosis?

Lysis of the cell.

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

Lysosomal enzymes exiting the dying cell would damage surrounding cells.

The toxin of Vibrio cholerae causes profuse diarrhea because it

Modifies a G protein involved in regulating salt and water secretion.

Which of the following is the best explanation for the fact that most transduction pathways have multiple steps?

Multiple steps provide for greater possible amplification of a signal.

When a cell releases a signal molecule into the environment and a number of cells in the immediate vivinity respond, this type of signaling is

Paracrine signaling.

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

Plant hormones may travel in air or through vascular systems.

Which of the following statements is true of signal molecules?

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

The general name for an enzyme that transfers phosphate groups from ATP to a protein is

Protein kinase.

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

Receptor tyrosine kinase activity.

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

Receptor tyrosine kinases.

The termination phase of cell signaling requires what?

Reversing the binding of signal molecule to the receptor.

From the perspective of the cell receiving the message, the three stages of cell signaling are

Signal reception, signal transduction, and cellular response.

What are chemical messengers that pass through the plasma membrane of cells and have receptor molecules in the cytoplasm?

Testosterone.

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

The active site of an allosteric enzyme in the cytoplasm that binds to a specific substrate.

In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following?

The growth factor is a paracrine signal.

When an excess of the ligand (hormone) is poured through the column after the receptor binding step, what do you expect will occur?

The ligand will cause the receptor to be displaced from the beads and eluted out.

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

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

Since steroid receptors are located intracellularly, which of the following is true?

The steroid/receptor complex can cross the nuclear membrane.

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

They amplify the original signal manyfold.

Because most receptors are membrane proteins, which of the following is usually true?

They change their conformation after binding with signal polypeptides.

What is true of transcription factors?

They control which genes are exprsesed.

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

They might not be able to multiply in response to growth factors from nearby cells.

What is/are true of ligand-gated ion channels?

They're important in the nervous system, they lead to changes in sodium and calcium concentrations in cells, and they open or close in response to a chemical signal.

The process of transduction usually begins

When the signal molecule changes the receptor protein in some way.

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?

a decrease in transcriptional activity of certain genes

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?

a form of cancer in which there is insufficient apoptosis

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

aggregation of bacteria that can cause cavities

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

alteration of protein kinases in cell cycle regulation in order to slow cancer growth

The human population's life expectancy has increased significantly but seems to have an upper limit. Which of the following might be described as an ecological consequence of passing that upper limit by regulating cell death?

an increase in the total population of humans on the planet

A major group of G protein-coupled receptors contains seven transmembrane α helices. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior face or on the cytosol face of the membrane. The loop on the cytosol side between helices 5 and 6 is usually substantially longer than the others. Where would you expect to find the carboxyl end?

at the cytosol surface

The coupled G protein most likely interacts with this receptor

at the loop between H5 and H6.

Testosterone functions inside a cell by

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

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

cAMP

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.

cAMP

Consider this pathway: epinephrine→ G protein-coupled receptor→ G protein→ adenylyl cyclase→ cAMP. Identify the second messenger.

cAMP.

The use of beta 2 antagonist drugs may be useful in asthma because they may

dilate the bronchioles by relaxing their smooth muscle.

Sutherland discovered that epinephrine signals

elevation of cytosolic concentrations of cyclic AMP.

Apoptosis involves:

fragmentation of the DNA, cell-signaling pathways, activation of cellular enzymes, & digestion of cellular contents by scavenger cells

One inhibitor of cGMP is Viagra. It provides a signal that leads to dilation of blood vessels and increase of blood in the penis, facilitating erection. Since cGMP is inhibited, the signal is prolonged. The original signal that is now inhibited would have

hydrolyzed cGMP to GMP.

GTPase activity is involved in the regulation of signal transduction because it

hydrolyzes GTP binding to G protein.

The function of phosphatases in signal transduction is best described as to

inactivate protein kinases and turn off the signal transduction.

Beta 2 antagonist drugs might also be used most effectively for which of the following?

increasing low blood pressure

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?

insufficient ATP levels in the cytoplasm

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

intracellular receptors are present only in target cells.

What are scaffolding proteins?

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

The toxin of Vibrio cholerae causes profuse diarrhea because it

modifies a G protein involved in regulating salt and water secretion.

Affinity chromatography is a method that can be used to purify cell-surface receptors, while they retain their hormone-binding ability. A ligand (hormone) for a receptor of interest is chemically linked to polystyrene beads. A solubilized preparation of membrane proteins is passed over a column containing these beads. Only the receptor binds to the beads. This method of affinity chromatography would be expected to collect which of the following?

molecules of purified receptor

The termination phase of cell signaling requires which of the following?

ncompatibility of the binding of the signal molecule to the receptor

Adenylyl cyclase has the opposite effect of what?

phosphodiesterase

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

phospholipase C

An inhibitor of phosphodiesterase activity would have what effect?

prolong the effect of epinephrine by maintaining elevated cAMP levels in the cytoplasm

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

protein kinase activity

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?

receptor tyrosine kinases

The receptors for a group of signaling molecules known as growth factors are often

receptor tyrosine kinases.

Protein phosphorylation is commonly involved with

regulation of transcription by extracellular signaling molecules, enzyme activation, activation of receptor tyrosine kinases, activation of protein kinase molecules.

In yeast signal transduction, the yeast cells

secrete molecules that result in response by other yeast cells.

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

serine and threonine

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

signal molecule

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

the active site of an allosteric enzyme that binds to a specific substrate.

If you wish to design an experiment to block the G protein-coupled receptor interaction, the block would preferentially affect which of the following?

the amino acid sequence in the binding site for the G protein

Where do apoptotic signals come from?

the nucleus, ER, ligand binding, mitochondrial protein leakage

The use of 2 beta antagonist drugs may be useful in asthma because

they may dilate the bronchioles by relaxing their smooth muscle

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

to block G protein activity in liver cells, or that increases phosphodiesterase activity.

Using the yeast signal transduction pathways, both types of mating cells release the mating factors. These factors bind to specific receptors on the correct cells

which induce changes in the cells that lead to cell fusion.