Chapter 16 - Part I - Cell Signaling Flashcards
Signaling cells produce _____ molecules.
signaling
Target cells detect the signal using a ____.
receptor protein
What term describes the extra cellular signal that is converted to an intracellular signal?
signal transduction
Regardless of the nature of the signal, the target cell responds by means of a specific protein called a ______, which binds the signaling molecule then initiates a response in the target cell.
receptor
Cells are typically exposed to many different types of signaling molecules. Cells are not responding all signals. Your cells respond to some signals but ignore others. What determines whether a cell responds to a signaling molecule?
Presence or absence of…. 1- Receptor 2- Intracellular signaling molecules and intracellular effector proteins 3- Combinations of signals give different responses
What are the 4 basic types of cell signaling?
Endocrine, paracrine, neuronal, contact-dependent
Which cell signaling is carries through the blood stream?
endocrine
Which cell signaling does not require the release of a secreted molecule such as a hormone and this method is used for very localized signaling event?
contact-dependent
Which cell signaling cell type is physically contacting each other?
contact-dependent
The cell signal type that remains in the neighborhood of the secreted cell type?
paracrine
The cell signal type that involves a local mediator?
paracrine
Which signal cell type involves the conversion of electrical impulses just like action potential into a chemical signals?
neuronal
Which signal cell type involves a neurotransmitter?
neoronal
Which cell type involves a hormone?
endocrine
Animal cell use ______ signal molecules to communicate with one another in various ways.
extracellular
Hormones are secreted by ____ cells into the bloodstream and are distributed widely throughout the body?
endocrine
Which cell signaling type involves long-range signaling?
endocrine
What type of signals diffuse in the extracellular fluid and as as local mediators on **on nearby cells**?
paracrine
In paracrine cell signaling, if the secreting cell itself responds, that is called ______ signaling.
autocrine
Many of the signal molecules that regulate inflammation at the site of an infection is ____ cell signaling.
paracrine
Cell signaling that involves neighborhood or self-signaling is ____.
paracrine.
What cell signaling involves a signal (neurotransmitter) that is delivered to a specific target cell at the synapse?
synaptic
What cell signaling involves direct signaling?
synaptic
Which cell signaling type involves the signaling molecule that is not released by the signaling cell?
contact-dependent
Which cell signaling type is important for the embryonic development and immune response and cell-to-cell communication via direct contact without the diffusion of signaling molecule?
contact-dependent
Many of the same types of signal molecules are used for endocrine, paracrine, and neuronal signaling. The crucial difference lies in the ______ and _____ with which the signals are delivered to their targets.
speed; selectivity
Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance, and 4 the type of signaling in which the signal molecule travels the largest distance. ___ paracrine signaling ___ contact-dependent signaling ___ neuronal signaling ___ endocrine signaling
3, 1, 2, 4
Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the largest distance, and 4 the type of signaling in which the signal molecule travels the least distance. ___ paracrine signaling ___ contact-dependent signaling ___ neuronal signaling ___ endocrine signaling
2, 4, 3, 1
Extracellular signal molecules bind either to ____ receptors or to ____ receptors.
cell-surface; intracellular
Signal molecules can be protein, peptide, amino acid, steroid, nucleotides, ions, or even dissolved gases. True or False?
True
Cell-surface receptors and binding occur inside the cell. True or false?
False. The extracellular signal molecule is huge and hydrophilic and can not enter the cell.
Cell-surface receptors and binding occur outside the cell. True or false?
True
Intracellular receptors involve large, hydrophilic molecules and an intracellular receptor. True or false?
False. It involves a small, hydrophobic signal molecule.
Intracellular receptors involve small, hydrophobic molecules and an intracellular receptor. True or false?
True
All cell types respond to acetylcholine the same. True or false?
False. Different cell types respond to acetylcholine differently.
Without signals, most cells undergo a form of cell suicide known as ___.
apoptosis
Cell responses that include molecular events like the release of vesicles, and firing action potentials are very (rapid or slow?)
rapid
A fast cell response involves a change in ___ activity.
protein
A slow cell response involves a change in _____, _____ and _____.
gene expression; cell growth; division
Altered protein synthesis is a (fast or slow?) cell response.
slow
Altered protein function is a (fast or slow?) cell response.
fast
Why does gene expression take longer?
The gene will need to be transcribed then mRNA will need to be translated and the protein needs to be accumulated to high enough levels to initiate changes. So that takes time.
Extracellular signaling molecules can bind ____ receptors or ___ receptors.
cell-surface; intracellular
The location of a receptor depends on whether the signaling molecule is ___ or ____.
polar; nonpolar
Cell-surface receptors are also called _____ receptors.
transmembrane
Name two types of hormones that cross the plasma membrane and bind intracellularly.
steroid and thyroid hormones
___ and ___ hormones are hydrophobic molecules that bind nuclear receptors promoting transcription.
steroid; thyroid
What type of hormones are cortisol, estradiol and testosterone?
steroid
What type of hormone is thyroxine?
thyroid
Which steroid hormone is produced in the adrenal glands in response to stress?
cortisol
Cortisol is nonpolar and can easily cross the membrane. Where are the receptors located?
cytosol
For nonpolar signaling molcules, the receptors are located on the surface on the cell. True or false?
False. The receptors are NOT located on the surface of the cell.
Steroids are (hydrophilic or hydrophobic?)
hydrophobic
Some gases diffuse across the plasma membrane and bind intracellularly. Nearby nerve endings release ____ triggering the production of ___ acid.
acetylcholine; nitric
DIffusion of ___ from the endothelial cells promotes relaxation of adjoining smooth muscle cells.
nitric acid
Diffusion of nitric oxide from the endothelial cells to the smooth muscle promotes ____ of smooth muscle cell.
relaxation
____ triggers smooth muscle relaxation in a blood-vessel wall.
nitric oxide
____ has been used for almost 100 years to treat patients with angina- pain caused by inadequate blood flow to the heart muscle.
Nitroglycerine
In the body, ___ is converted to __, which rapidly relaxes blood vessels.
nitroglycerine; NO
____ reduces the workload on the heart and decreases the muscle’s need for oxygen-rich blood.
Nitric acid (NO)
_____ within an intracellular signaling pathway can **adjust the response** to an extracellular signal.
Feedback regulation
Intracellular signaling proteins are molecular _____.
switches
_____ turn on the signaling by protein phosphorylation.
Protein kinase
_____ turn off the signaling by protein phosphorylation.
protein phosphatase
_____ turn on the signaling by GTP-binding proteins.
GTP binding
_____ turn off the signaling by GTP-binding proteins.
GTP hydrolysis
What are the 3 types of extracellular receptors?
1- Ion-channel-coupled receptors;
2-G-protein-coupled receptors (GPCR);
3- Enzyme-coupled receptor
What type of receptors are signal binding that opens the channel which allows ions to cross the plasma membrane and hence, **alters the membrane potential**?
1- Ion-channel-coupled receptors;
Which extracellular receptor has seven transmembrane domains?
G-protein-coupled receptors
Signal binding to a GPCR ___ a G-protein. G-proteins activate ___ channels for enzymes.
activates; downstream
Which extracellular receptor involves a trimer?
GPCR
After signal binding, these enzyme-coupled receptor act as ___ or activate other ___.
enzyme enzymes
Which extracellular receptors were discovered for their role in responding to growth factors in animal cells?
enzyme-coupled receptor
The number of different types of receptors is ___ than the number of extracellular signals that act on them.
greater
Foreign substances like nicotine, morphine, and menthol exert their initial effects by ____.
interact with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.
Which family of receptors form the largest family of cell surface receptors?
GPCR
Why are GPCRs an attractive target for the development of drugs to treat many disorders?
They mediate responses to an enormous diversity of extracellular signal molecules and are involved in a large variety of cell processes.
About 1/3 of all drugs are used today to work through ___.
GPCRs
What are the 2 main types of GTP binding proteins that participate in intracellular signaling pathways?
1- Large, trimeric GTP-binding proteins (aka G proteins); 2- Small, monomeric GTPases
The monomeric GTP-binding proteins are aided by two sets of regulatory proteins. ____ activate the switch proteins by promoting the exchange of GDP for GTP. And ____ turn them off by promoting GTP hydrolysis.
Guanine nucleotide exchange factors (GEFs); GTPase-activating proteins (GAPs)
GPCR is the G protein. True or false?
False. GPCR is the receptor.
GPCR is a ___.
receptor
Monomeric GTPase activate when GEFs promote the exchange of ___ for ___.
GDP; GTP
Monomeric GTPase are inactivate when GAPs stimulate the hydrolysis of __ to ___.
GTP to GDP
G proteins and monomeric GTPases are active when GTP is bound and inactive when GDP is bound. True or false?
True
___ activate G-proteins upon signal binding.
GPCRs.
What are the 3 subunits for G-proteins? Which one binds to GTP?
alpha, beta, gamma; alpha
GPCR acts as a __ for the G-protein **activating** the alpha and beta-gamma subunits.
GEF (guanine exchange factor)
When a G-protein-coupled activates a G protein, what happens?
The alpha subunit exchanges its bound GDP for GTP.
Both the GTP-bound alpha subunits and nucleotide-free beta-gamma complexes - but not GDP- bound, fully assembled G proteins - can activate other molecules downstream of GPCRs. True or false?
True. Both are involved in downstream message delivery.
The amount of time that the alpha and beta-gamma subunits remain “switched on” determines how long a response lasts. True or false?
True
This time is controlled by the behavior of the __ subunit has an intrinsic GTPase activity.
alpha
As long as alpha subunit has GTP, it is off. True or False?
False. As long as alpha subunit has GTP, it is ON.
The length of time a G protein will signal is determined by ____.
the GTPase activity of G-alpha
Bacteria ___ G-protein activity.
exploit
Vibrio cholerae produces ___ toxin. It prevents __ protein from hydrolyzing ___ in intestinal cells. It And constitutively active __ results in diarrhea and dehydration.
cholera; G_s; GTP; G_s
Bordetella pertussis produces __ toxin. It prevents the __ protein from exchanging GDP to GTP in the lungs. And constitutively inactive __ stimulates coughing.
pertussis; G_i; G_i
G-protein-coupled receptors (GPCRs) all have a similar structure with ___ transmembrane domains.
7
When a GPCR binds an extracellular signal an intracellular G protein, composed of __- subunits, become acticated.
3
__ of the G-protein subunits are tethered to the plasma membrane by short lipid tails.
2
When unstimulated, the alpha subunit is bound to ___, which is exchanged for ___ on stimlation.
GDP; GTP;
The intrinsic ___ activity of the alpha subunit is important for inactivating the G protein.
GTPase
___ inhibits this activity of the alpha subunit, thereby keeping the subunit in an active site.
Cholera
Some G-proteins regulate ion channels. This is __ response.
rapid
Heart muscle cells is an example of __ response.
rapid
In the heart muscle cells, the acetylcholine ___ muscle contraction via ___ signaling cascade.
inhibits; GPCR
Binding of the neurotransmitter ___ to its GPCR on the heart cells results in the activation of the G protein, G_i.
acetylcholine
The ___ directly opens a __ channel in the plasma membrane, increasing its permeability to __ and thereby making the membrane harder to activate and ___ the heart rate.
activated beta-gamma complex; K+; K+; slowing
Inactivation of the __ by hydrolysis of its bound GTP returns the G protein to its inactive state, allowing the __ channel to close.
alpha; K+
G-proteins can activate membrane-bound enzymes creating __ or __ messengers.
small; second
What is the second messenger for the following enzyme: adenylyl cyclase?
cyclic AMP (cAMP)
What is the second messenger for the following enzyme: phospholipase C?
IP3 and DAG
Second messenger molecules ___ to act on intracellular signaling proteins.
diffuse
The alpha subunit of G_s activates ____ generating ___ from ATP.
adenylyl cyclase; cAMP
cAMP activates cyclic-AMP-dependent ___.
PKA
PKA __ other proteins changing their activity.
(Think… What does PKA stand for?)
phosphorylates
cyclic AMP phosphodiesterase continuously converts ___ to ___ (down-regulating the activity).
cAMP; AMP
Caffeine acts as a stimulant by inhibiting ___ in the nervous system, blocking cyclic AMP ___ and keeping the concentration of cyclic AMP ___.
cyclic AMP phosphodiesterase; degradation; high
Give an example where the response to a signal and the increase in cAMP can be rapid. Why does this occur?
Skeletal muscle; These reactions do not involve changes in gene transcription or new protein synthesis
Give an example where the response to a signal and the increase in cAMP can be slow.
neuronal learning memory
G_q activates ____ which cleaves ____ to form the second messengers ___ and ___.
phospholipase C; inositol phospholipid; IP3; DAG
Vasopressin (a peptide hormone) a) Targets what tissue? b) What’s the major response?
a) liver b) glycogen breakdown
Acetylcholine. If the target tissue is the pancreas, what is the major response?
secretion of amylase (a digestive enzyme)
Acetylcholine. If the target tissue is the skeletal muscle, what is the major response?
contraction
Thrombin (a proteolytic enzyme) a) Targets what tissue? b) What’s the major response?
a) blood platelets; b) aggregation
Which of the following types of cell signaling is long range and uses hormones as signals?
Endocrine
The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is…
binding of the signal molecule to a receptor.
The active form of a monomeric GTP-binding protein is the…
GTP-bound form.
What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute?
one that involves a change in gene expression
The length of time a G protein will signal is determined by _______.
the GTPase activity of Gα.
Foreign substances like nicotine, morphine, and menthol exert their initial effects by _____.
interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus.
One of the two types of GTP-binding proteins, often called G-proteins, are membrane bound. These are the
trimeric GTP-binding proteins.
Which of the following would produce the fastest response to G-protein activation?
ion channel activation
Signaling molecules that a cell secretes may act as local mediators, affecting only cells in the immediate environment of the signaling cell, in a process called________________________.
paracrine
All members of the steroid hormone receptor family are found where in the cell?
Cytosol
. Circle the phrase in each pair that is likely to occur more rapidly in response to an extracellular signal.
A. changes in cell secretion / increased cell division
B. changes in protein phosphorylation/changes in proteins being synthesized
C. changes in mRNA levels / changes in membrane potential
A. changes in cell secretion
B. changes in protein phosphorylation
C. changes in membrane potential
Given the generic signaling pathway in the figure below, write the number corresponding to the item on the line next to the descriptor.
Receptor Protein 2
Effector proteins 4
Intracellular signaling proteins 3
Ligand 1
Match the cell-surface receptors with the best description of function. Not all descriptors will be used.
G-protein-coupled receptors ______
ion-channel-coupled receptors ______
enzyme-coupled receptors ______
A. alter the membrane potential directly by changing the permeability of the plasma membrane
B. signal by opening and closing in a ligand-independent manner
C. must be coupled with intracellular monomeric GTP-binding proteins
D. all receptors of this class are polypeptides with seven transmembrane domains
E. discovered for their role in responding to growth factors in animal cells
D
A
E
Two main types of protein kinases operate in intracellular signaling pathways: the most common are
1- serine/threonine kinases;
2- tyrosine kinases
What are the two main types of GTP binding proteins that participate in intracellular signaling pathways?
1- Large, trimeric GTP-binding proteins (also called G proteins);
2- small, monomeric GTPases
Which binding proteins relay messages from G-proteins-coupled receptors (GPCR)?
Large, trimeric GTP-binding proteins (also called G proteins)
Which binding proteins to help relay their signals
small, monomeric GTPases
These monomeric GTP-binding proteins are aided by two sets of regulatory proteins. What are they?
1- Guanine nucleotide exchange factors (GEFs)
2- GTPase-activating proteins (GAPs)
a) What activates the switch proteins by promoting the exchange of GDP for GTP?
b) What turns the above off by promoting GTP hydrolysis?
a) Guanine nucleotide exchange factors (GEFs)
b) GTPase-activating proteins (GAPs)
