CHAPTER 9

The system of communication between cells through signaling pathways is called homeostasis

False

In the livers, the enzyme glycogen phosphorylase catalyzes the breakdown of glucose

False

Steroid hormones, such as testosterone and estrogen, are polar signaling molecules

False

After the binding of a signaling molecule to a surface receptor , the signaling molecule does not enter the cell

True

After signal transduction has run its course, receptor molecules are removed from the surface by endocytosis; one possible fate of the receptor is to be separated from its signaling molecule and returned to the cell surface

True

G-protein coupled receptors are found in both prokaryotes and eukaryotes

False

In plants the IP3/DAG pathways control the organism/s responses to water loss and changes in light intensity 

True

Steroid hormones are nonpolar molecules derived from cholesterol

True

In breast cancer, Era is often lost, which increases cell proliferation

False

Cross-talk between second messenger pathways is probably involved in particular types of olfactory signal transduction in many animals.

True

In order for a target cell to receive a signal, it must possess a _______ specific to the signaling molecule

Receptor

Adjacent animal cells utilize _______ to rapidly communicate with each other

Gap Junctions

Adjacent plants cells utilize ____ to rapidly communicate with each other

Plasmodesmata

How do cells in the body of a multicellular organism communicate with each other

by way of signaling molecules that interact with specific receptors

Substance B is synthesized in neurons, travels through gap junctions, and triggers the transduction of an electrochemical signal. This is an example of _____ 

communication by direct contact 

If Substance A is synthesized in the liver , travels through the circulatory system bound to a carrier protein, and causes a change in gene expression in a target cell. This is an example of ____

long-distance signaling

In order for a cell to respond to the signaling molecule epinephrine, it must have

receptors with an epinephrine binding site on the plasma membrane surface

Receptors for polar molecules are found _____, while receptors for nonpolar molecules are located

on the cell surface, within the cell

Non polar signaling molecules enter the cell by

simple diffusion

An example of a nonpolar signaling molecule is 

testosterone

How does a cell surface receptor respond to the binding of a signaling molecule

the signal is transduced through the plasma membrane and into the cell 

the overall process by which information carried by a signaling molecule is translated into changes that occur inside the cell is called signal

transduction

You have recently identified a molecule you believe to be a signaling molecule associated with signal transduction. All you know about this molecule is that it is hydrophilic; therefore, you expect it to interact with a receptor ____.

on the cell surface 

In the 1950s, Earl Sutherland and colleagues discovered that epinephrine ____.

triggers the release of a second messenger which leads to the hydrolysis of glycogen to glucose 

In general, a cell receiving a message undergoes three stages of cell signaling. What are these stages? a. paracrine, autocrine, and local

signal reception, signal transduction, and cellular response

A pathway for cell growth control is conserved between Drosophila and humans, indicating that the pathway is ____.

at least 800 million years old 

In the process of quorum sensing, bacteria release signaling molecules in ____ concentrations as cell density ___

increasing ; increases 

Quorum sensing

is a type of communication between unicellular organisms 

The evolution of which class of molecules played an important role in the development of multicellular organisms

Protein kinases

he two major categories of extracellular signaling molecules that bind to cell surface receptors are

peptide hormones and neurotransmitters

Neurotransmitters are molecules released by _____

neurons

The surface receptors that recognize and bind signaling molecules are ___

glycoproteins 

The recognition of a chemical signal by a receptor protein in the membrane is most similar to ____

binding of a specific substrate to the active site of an enzyme 

The last protein in a signaling pathway is called the

Target protein

Amplification of a signal increases as the ____

number of enzyme-catalyzed steps increases

n the first step of signal transduction, what is the trigger for the cellular response

ligand

What is the second step of signal transduction

transduction

Protein kinases

Add phosphate groups to proteins 

The effects of protein kinases are reversed by another group of enzymes called

phosphatases

Once transduction of a signal is complete, the receptor and its bound signaling molecule are removed from the cell surface by ____

Endocytosis

he protein kinase activity of the receptor tyrosine kinase (RTK) is located ____ region of the protein

on the cytoplasmic

During autophosphorylation, RTKs add phosphate groups to which amino acids

Tyrosine

What happens immediately after a signaling molecule binds to an RTK?

receptor dimerization

Structurally similar RTKs have been found in all multicellular animals, suggesting that

RTKS evolved relatively early in the history of animals

The insulin receptor is an example of a(n) _

receptor tyrosine kinase

Substance E is made in the pancreas, travels through the blood, and binds to a surface receptor on a target cell. After dimerization and autophosphorylation, the receptor activates a signaling protein. Substance E is therefore the ligand for

a receptor-tyrosine kinase

Arrange the events in the pathway activated by G - protein - coupled receptors (GPCRs) in the correct order

3—>5—>1—>4—>2

Inactive G proteins are

bound to GDP

Activated G proteins

separate into two parts How many transmembrane domains are present in a G - protein - coupled receptor?

How many transmembrane domains are present in a G - protein - coupled receptor?

Seven

Many of the different types of GPCRs in humans function to

distinguish different volatile molecules for odor recognition

More than 60% of all prescribed drugs target ____, due to their wide physiological impact

G-protein-coupled-receptors

G proteins are inactivated when

GTP is converted to GDP

Many signal transduction pathways utilize second messengers to 

relay the message from the inner surface of the plasma membrane throughout the cytoplasmThe amino acid targets of protein kinases in all GPCR pathways are ____

The amino acid targets of protein kinases in all GPCR pathways are ____

serine and threonine

which molecule is a common second messenger

Diacylglycerol

In the cAMP pathway, the G protein activates

Adenylyl cyclase

Once activated , cAMP is quickly degraded to AMP by_____, switching off the signal pathway . 

phosphodiesterase

In the IP3/DAG pathway, what is the effector molecule

phospholipase C

Substance C is secreted from a neuron, and binds to its receptor on a nearby cell, triggering an increase in intracellular cAMP. Substance C is therefore a ligand for a ____

a G-protein coupled receptor

Ras proteins are of interest to researchers because of their role in ____.

the development of many types of cancer

Inactive Ras is bound to receptor tyrosine kinases by

Adapter proteins

Activated Ras__

activates MAP kinase (MAP K)

Acetylcholine, a neurotransmitter, binds to ____.

ligand-gated ion channels

Which cellular response follows activation of a ligand - gated ion channel?

generation of an electrical signa

A neuron synthesizes and secretes substance D, which binds to a receptor on the neuron cell membrane, triggering an influx of calcium. Substance D therefore is a ligand for a ___

a ligand gated ion channel

Steroid and thyroid hormones do not bind to membrane surface receptors because they

are soluble in the lipid bilayer

Steroid hormones

include testosterone, estrogens, and cortisol

Why are steroid hormones bound to carrier proteins in the blood

to mask hydrophobic groups on the steroids to allow for circulation in the blood

How do cells distinguish between estrogen and testosterone?

estrogen and testosterone have the same basic structures, but different side chains that are easily distinguished by their individual receptors

Estrogen receptor (ER) α typically ____, while ERβ typically ___

stimulates cell proliferation; inhibits cell proliferation

Researchers have determined that the growth of hormone - responsive breast cancer cells depends upon __

the relative concentrations of ERα and ERβ in the tumor cells

Hormone receptors are comprised of two domains, the hormone binding domain and the ____, which triggers the cellular response

DNA - binding domain

Substance A is secreted by the liver, travels through the circulatory system bound to a carrier protein and causes a change in gene expression in its target cell. Substance A is therefore a ligand for ____

a steroid hormone receptor

Nitric oxide(NO)binds to an

internal receptor and activates a second messenger cascade

NO can only function as a paracrine regulator because____.

it is rapidly converted into nitrates and nitrites 

How is the NO pathway manipulated by Viagra to treat erectile dysfunction?

the breakdown of cGMP is inhibited

NO binds to and activates____ to trigger its cellular response.

guanylyl cyclase

Communication and integration of responses between simultaneously occurring cell signaling pathways is called

cross- talk 

Hormone - independent steroid hormone receptor activation is an example of

cross- talk 

cell communication by direct contact

D

paracrine regulation 

A

autocrine regulation

b

long-distance signaling 

C

communication used by neurotransmitters acting on neuron across a synapse 

A

communication used by cardiac muscle cells to synchronize heart contractions 

D

meditation of the fight or flight response by epinephrine

C

binds to an activates the enzyme guanylyl cyclase

Nitric oxide

directly bind to DNA to affect transcription 

hormone receptors 

Lithium reduces the activity of this pathway

IP3/ DAG

G protein activated by a receptor tyrosine kinase

Ras

Binds to acetylcholine

ligand gated ion channel

Pathway triggered by glucagon to stimulate glycogen breakdown

cAMP

Defects in this receptor type can lead to diabetes and dwarfism

receptor tyrosine kinase

Converts an extracellular signal into an intracellular response 

signal transduction