Chapter 9 Bio

benefit of intracellular signalling What is the advantage to the cell of a signaling molecule entering directly into the cell, and binding to and activating a receptor that can induce transcription of DNA? A wide variety of responses can be elicited The signal can be greatly amplified within the cell The signal cascade can be more tightly regulated than when extracellular signaling molecules are used A change in gene expression can be quickly accomplished the signaling molecule itself is able to regulate gene expression

A change in gene expression can be quickly accomplished

Mechanism of acetylcholine action Acetylcholine is a signaling molecule, a neurotransmitter, that is produced in response to many different stimuli. It binds to diverse receptors, and activates different responses in a variety of cells. For instance, it activates contractions in skeletal muscle and inhibits contractions in cardiac muscle. It functions in the central nervous system to make a person aware and awake. Which of the following statements about acetylcholine is FALSE? Acetylcholine is capable of eliciting many different responses due to the receptors it binds to and the second messengers that are produced within the cytoplasm of the cell. Acetylcholine triggers many different responses throughout the body so that a coordinated response can be induced due to specific stimuli. Acetylcholine will only bind to and open sodium channels in order to activate a response in a cell.

Acetylcholine is capable of eliciting many different responses due to the receptors it binds to and the second messengers that are produced within the cytoplasm of the cell.

Transcription factors

Activate gene expression Change in sex characterstics

Picture Aldosterone is hydrophobic and can diffuse across the lipid bilayer, while acetylcholine is charged and cannot pass the lipid bilayer Aldosterone does not require a receptor to elicit a response, but acetylcholine must bind to a receptor to transduce a signal Signaling with aldosterone results in gene transcription, while signaling acetylcholine results in an increase in metabolic processes Aldosterone can bind to DNA, but acetylcholine must bind to receptors

Aldosterone is hydrophobic and can diffuse across the lipid bilayer, while acetylcholine is charged and cannot pass the lipid bilayer

structural proteins

Altering cell shape causing cell movement

Enzyme

Altering metabolism Associated with the breakdown of molecules

Which statement best describes the advantage of second messengers? The advantage of second messengers is best described as Amplification of the signal Speeds up ligand-receptor binding Prevention of signal inhibition Enhanced specificity of the ligand Replaces the role of protein phosphatases

Amplification of the signal

How does light affect the distribution of auxin produced by a plants growing shoot tip?

Auxin causes cells to elongate.The cells on the non illuminated side accumulate more auxin, which causes this side to grow faster and bend toward the light .

Differential responsiveness to epinephrine Epinephrine inhibits salivary gland activity and muscle cell contraction in the airways, yet stimulates glycogen release in muscle cells and heart muscle cell contraction. How could one hormone have opposing effects on different organs? Cells in the tissues that are suppressed do not express an epinephrine receptor. Cells in responsive tissues have signal transduction pathways. Only responsive tissues are exposed to the epinephrine in the blood stream. Cells in tissues that are not responsive contain enzymes that break down epinephrine when it enters the cell. Cells in the different tissues would have epinephrine receptors coupled to different signaling pathways.

Cells in the different tissues would have epinephrine receptors coupled to different signaling pathways.

Channel proteins The sodium channel is formed by a channel protein. Which of the following statements about channel proteins is TRUE? Channel proteins cannot be regulated by the cell. Channel proteins couple the movement of a molecule to ATP hydrolysis, which provides energy for its active transport. Channel proteins can be opened or closed by cell signaling molecules. The same molecule that opens a channel protein will also be transported by the channel protein. Channel proteins are involved in both active and passive transport.

Channel proteins can be opened or closed by cell signaling molecules.

In____, signals pass through a cell junction from one cell to adjacent cells.

Direct intracellular signaling

Cells release signals that travel long distances to affect target cells during.

Endocrine signaling

Which type of cell signal,paracrine or endocrine,is likely to exist for a longer period of time? explain why this is necessary?

Endocrine signals are more likely to exist for a longer period of time.This is necessary because endocrine signals called hormones travel relatively long distances to reach their target cells.therefore, the hormone must exist long enough to reach its target cells.

Epinephrine has to cross the cell membrane t... Epinephrine has to cross the cell membrane to bind to its receptor in the cytoplasm. True False

False

The G-protein changes conformation when the GTP replaces The G-protein changes conformation when the GTP replaces the GDP on the alpha subunit. True False

False

The mRNA molecule moves from the cytoplasm to the nucleus and binds The mRNA molecule moves from the cytoplasm to the nucleus and binds to a ribosome where it directs the synthesis of specific proteins. True False

False

The second messenger cAMP is made from ADP. The second messenger cAMP is made from ADP. True False

False

The binding of epinephrine to its receptor a... The binding of epinephrine to its receptor activates a(n) A protein. D protein. G protein. K protein. M protein.

G protein.

G-protein activation Which statement regarding G-protein activation is TRUE? G-proteins are activated when they are bound by an extracellular signaling molecule G-proteins are activated by the alpha subunit separating from the beta/gamma subunit G-proteins are activated by active G-protein-linked receptors G-proteins are activated by Ca2+ Only the alpha subunit of the G-protein is active

G-proteins are activated by active G-protein-linked receptors

In____, cells release signals that affect nearby target cells.

Paracrine signaling

Intracellular receptors are activated by signaling molecules that____ the plasma membrane.

Pass through

Most types of enzyme-linked receptors function as______.

Protein kinases

Na+ enters the cell Why is it possible for Na+ to enter the cell when the channel is open? ATP is used to provide energy to pump Na+ It is co-transported with a molecule that is moving down its gradient Na+ are only capable of moving inside the cell The Na+/K+ pump previously built a high concentration of Na+ on the outside of the cell, so Na+ is diffusing Na+ first moves out of the cell across the lipid bilayer by simple diffusion, and then enters the cell by facilitated diffusion

The Na+/K+ pump previously built a high concentration of Na+ on the outside of the cell, so Na+ is diffusing

For most signaling molecules,explain why signal transduction pathway is necessary.

The effect of a signaling molecule is to cause a cellular response.most signaling molecules do not enter the cell.Therefore,to exert an effect,they must alter the conformation of a receptor protein which,in turn,stimulates an intracellular signal transduction pathway that leads to a cellular response.

mutation of a G-protein-linked receptor If a ligand were stuck in the G-protein-linked receptor, what would be the effect to the cell? The pathway would be over active The pathway would not be activated, even though the signal was present The pathway would be deactivated by the phosphorylase activity of the G-protein's alpha subunit The pathway would be deactivated when GDP replaced GTP in the alpha subunit The cell would stop producing the signal molecule that got stuck

The pathway would be over active

mutation in the aldosterone receptor A cell has a mutation resulting in the aldosterone receptor being unable to efficiently bind to DNA. What effect will this have on the cell? Aldosterone cannot be released in the blood as a signaling molecule Aldosterone will not be able to bind to its receptor in the cytoplasm, so the signaling pathway will not elicit its response The receptor will become active, but once inside the nucleus it will not be able to initiate transcription, so the signaling pathway will not elicit its response. mRNA will be transcribed, but protein translation will not occur properly, so the signaling pathway will not elicit its response.

The receptor will become active, but once inside the nucleus it will not be able to initiate transcription, so the signaling pathway will not elicit its response.

Inactivation of the alpha subunit occurs when its own phosphorylase activity removes a phosphate from the GTP. True False

True

The combination of the calcium and the calmodulin produces The combination of the calcium and the calmodulin produces the response of the cell to the ligand. True False

True

The sodium channels in the cell membrane have receptor The sodium channels in the cell membrane have receptor sites for acetylcholine. True False

True

The ultimate result of lipid-soluble hormones on cells The ultimate result of lipid-soluble hormones on cells is the production of proteins. True False

True

The alpha subunit's separation from the remainder of the G-protein can be repeated as long as the ligand is bound to the receptor. True False

True...

Initially, bound to the alpha subunit of the G-protein is... When inactive, the alpha subunit of the G-protein is bound to a ligand. a GTP molecule. a GDP molecule. an ADP molecule. a GTO molecule.

a GDP molecule

____ binds receptors inside cells a.estrogen b.epinephrine c.epidermal growth factor d.all of the above e.none of the above

a.estrogen

The second messenger cAMP is synthesized by the enzyme adenylyl cyclase. cAMP phosphodiesterase. ATPase. ligase. phosphorylase.

adenylyl cyclase.

The ligand that activates the G-protein linked receptor is an extracellular signaling molecule GTP Ca2+ a G-protein a second messenger

an extracellular signaling molecule

An example of___ is when cells release signals that affect themselves and nearby target cells.

autocrine signaling

which statement best describes the extrinsic pathway for apoptosis? a.capases recognize an environmental signal and expose their death domain b. death receptors recognize an environmental signal, which then leads to the activation of caspases. c.initiator caspases digest the nuclear lamina and cytoskeleton dexecutioner caspases are part of the death-inducing signaling comple(DISC). e.all of te above

b.death receptors recognize an environmental signal, which then leads to the activation of caspases.

Once inside of the cell, these lipid soluble hormones... Once inside of the cell, these lipid soluble hormones... bind with a DNA molecule. bind with a specific receptor molecule inside the nucleus. bind with a mRNA molecule. bind with a specific receptor molecule inside the cytoplasm. bind with a ribosome.

bind with a specific receptor molecule inside the cytoplasm.

when cells secretes a signaling molecule that binds to receptors on neighboring cells as well as the same cell, this is called___ signaling a. direct intercellular b.contact-dependent c.autocrine d.paracrine e.endocrine

c.autocrine

In extracellular signaling,ligands bind to_____.

cell surface receptors

Membrane-bound signals bind to receptors on adjacent cells in the process of ____.

contact dependent signaling

An agant that allows a cell to respond to changes in its environment is termed a. a cell surface receptor b.an intracellular receptor c. a structural protein d. a signal e.apoptosis

d. a signal

which of the following does not describe a typical cellular response to signaling molecules? a. activation of enzymes within the cell b. change in the function of structural proteins,which determine cell shape c. alteration of levels of certain proteins in the cell by changing the level of gene expression d.change in a gene sequence that encodes a particular protein e. all of the above

d.change in a gene sequence that encodes a particular protein

small molecules,such as cAMP, that relay signals within the cell are called a.first messengers b.ligands c. G proteins d.second messengers e.transcription factors

d.second messengers

Lipid soluble hormones... Lipid soluble hormones... require a membrane receptor protein to enter the cell. diffuse through the cell membrane. enter the cell through active transport. work as ligands on the surface of the cell membrane. require specific gates to pass through the cell membrane.

diffuse through the cell membrane.

all cells of a multicellular organism may not respond in the same way to a particular ligand(signaling molecule) that binds to a cell surface receptor.the difference in response may be due to a. the type of receptor for the ligand that the cell expresses b.the affinity of the ligand for the receptor in a given cell type. c. the type of target proteins that the cell expresses e. all of the above

e. all of the above

Apoptosis is the process of a.cell migration b.cell signaling c.signal tranducation d. signal amplification e. programed cell death

e. programed cell death

the benefit of second messangers in signal transduction pathways is a.an increase in the speed of a cellular response b.duplication of the ligands in the system c.amplification of the signal d.all of the above e.a and c only

e.a and c only

a receptor has a Kd for its ligand of 50 NM. this receptor a.has a higher affinity for it ligand than does a receptor with a Kd of 100nM b has higher affinity for its ligand than does a receptor with a Kd of 10 nM c.is mostly bound by its ligand when the ligandwhen the ligand concentration is 100 nM d.must be an intracellular receptor e.both a and c

e.both a and c

Nicotine and acetylcholine Nicotine is a molecule that is chemically similar to acetylcholine and binds to the same receptors. What affect will nicotine have on the cell shown in the animation? it will open sodium channels It will close sodium channels It will kill the cell It will excite the cell It will depress the cell

it will open sodium channels

The enzyme a-kinase adds ________ to protein... The enzyme alpha-kinase adds ________ to proteins. acetates benzoates carbonates phosphates hydroxyls

phosphates

The alpha subunit of the G-protein is activated by separating from the gamma and beta subunits. the G-protein becoming phosphorylated. binding to the calcium ions. replacing the GDP with GTP. replacing the GTP with GDP.

replacing the GDP with GTP.

In mammals,receptors for_____are intracellular.

steroid hormones

As a result of the ligand binding to its site... As a result of the ligand binding to its site on the G-protein-linked receptor the G-protein changes conformation and GTP replaces the GDP on the alpha subunit. the G-protein changes conformation and the alpha subunit separates from the beta and gamma subunits. the G-protein changes conformation and GDP replaces the GTP on the alpha subunit. the G-protein changes conformation and the alpha subunit rejoins the beta and gamma subunits. the G-protein changes conformation and GTP on the alpha subunit is hydrolyzed, forming GDP.

the G-protein changes conformation and GTP replaces the GDP on the alpha subunit

Mutation in a G-protein 2 A mutation in the G-protein, decreasing its ability to hydrolyze its bound GTP, will have what effect on the cell signaling pathway in which it is involved? the pathway will be under expressed the pathway will be over expressed the pathway will be expressed, even in the absence of a signal the pathway will be activated by other receptors, such as receptor tyrosine kinases The cell will cease to activate the G-protein linked receptor

the pathway will be over expressed

Mutation in a G-protein A mutation that alters the G-protein's affinity for GDP, making it less likely to release GDP even when stimulated by a receptor, will have what effect on the cell signaling pathway in which it is involved? the pathway will be under expressed the pathway will be over expressed the pathway will be expressed, even in the absence of a signal the pathway will be activated by other receptors, such as receptor tyrosine kinases The cell will cease to activate the G-protein linked receptor

the pathway will be under expressed

When the acetylcholine binds to the receptor sites... When the acetylcholine binds to the receptor sites... a ligand is formed. the sodium channels open. the sodium channels remain closed. sodium ions diffuse through and enter the cell. sodium ions diffuse through and leave the cell.

the sodium channels open.

When the acetylcholine receptor sites are not occupied... a ligand is formed. the sodium channels open. the sodium channels remain closed. sodium ions diffuse through and enter the cell. sodium ions diffuse through and leave the cell.

the sodium channels remain closed.