Chapter 9- PowerPoint Flashcards
What are the 3 ways cells communicate with eachother?
1) direct contact
2) local signaling
3) long-distance signaling
What are the 3 steps in how target cells process the signal?
1) reception
2) transduction
3) response
What is the cell that sends the signal?
signaling cell
What is the cell that receives the signal?
target cell
What does communication between cells require?
ligand and receptor protien
what is a ligand?
signaling molecule
Where are receptor proteins located?
plasma membrane or within the cell
what is a receptor protein?
molecule to which the signal binds
How does polarity affect the location of receptor proteins?
determines if the receptor protein is located on in the plasma membrane or within the cell
What is Direct contact?
molecules on the surface of one cell are
recognized by receptors on the adjacent cell
What is an example of a direct contact junction?
gap junctions
What is an example of a direct contact in plants?
plasmodesmata
What are the 3 types of local signaling?
paracrine signaling, synaptic signaling, and autocrine signaling
What is paracrine signaling?
signal released from a cell has an effect on neighboring cells
What is synaptic signaling?
signaling between neurons
What is autocrine signaling?
local regulator acts on the same cell that it produces it
What is the “synapsis” of muscle cells?
neural muscular junction
Where does synaptic signaling also occur?
muscle cells
What is long distance signaling?
A controlling cell secretes a signaling molecule (hormone) which produces a response in target cells that may be far away
What’s the most common means of cell communication?
long distance signaling
Do all cells contain receptors for all signaling moleuces?
no
What happens when something binds to a receptor protien? what is it called?
changes proteins conformation, called activation
What kicks off transduction?
activation of receptor protein
What is the first messenger?
ligand
Where are the location of the 1st and 2nd messenger?
1st is outside the cell
2nd is indside the cell
In which experiment did we understand the concept of the second messenger?
southerland’s experiment
What did they find in breast cancer cells?
increase in epidermal growth factors
What did they find in breast cancer cells?
increase in epidermal growth factors
What is GPCR?
G protein-coupled receptor
What are the 3 subunits the form trimeric G protein?
alpha, beta, gamma
Is the trimeric G protein large?
yes
What does G-protein active mean?
binds to GTP
What does G-protein inactive mean?
binds to GDP
Where does the receptor bind?
alpha subunit
What happens when the alpha subunits when a receptor binds?
gives up GDP and separates from the beta-gamma
How do hormones move around in animals?
circulatory system
How do hormones move around in plants?
moving through cells
—some are gases that diffuse through the air
What is reception?
binding of a signal molecule
with a specific receptor on a target cell
Where do receptors for polar signal molecules have a binding site?
cell surface
Where do receptors for nonpolar signal molecules have a binding site?
within the cell
What is an example of polar signal molecule?
epinephrine
What is an example of nonpolar signal molecule?
steroid hormones
What is transduction?
changes a signal into a form that causes a cellular response
What can trigger a cellular response?
proteins and second messengers
What was the response in Sutherland’s work?
activation of enzyme glycogen phosphorylase
What is signal transduction?
When activated receptor initiates a whole host of responses within the cell
Is the combination of surface receptors on a particular cell type fized?
nope, changes as cells develop
What are the 3 subclasses of membrane receptors?
channel linked, enzymatic, and G protien-coupled receptor
What is a channel linked receptor?
ion channel that opens in
response to a ligand
What are enzymatic receptors?
receptor is an enzyme that is activated by the ligand (receptor tyrosine Kinases)
What is a G protein-coupled receptor?
a G-protein (bound to GTP)
assists in transmitting the signal
What are the 2 types of G proteins?
Ras and Trimeric
Which G protein is monomeric?
Ras
Which G protein binds to GTP in their active form and GDP in their inactive form?
Both Ras and Trimeric
Which G protein does the guanine nucleotide bind to the alpha subunit?
trimeric
What are GPCRs?
- G-protein is a switch turned on by the receptor
- G-protein activates an effector protein (enzyme) which is membrane bound
What activates GPCRs?
first messenger
What does binding of GPCR do?
activates the effector
How does the G-protein subunit inactivates itself?
hydrolyzing GTP to GDP
What does the activated effector do?
generates internal, nonprotein signal
molecules called second messengers
What do second messengers do?
directly or indirectly activate protein
kinases, which initiate cellular response by phosphorylating
specific target proteins
What is effector?
enzyme that can make a second messenger
When is the G-protein activated? What happens after this?
when GTP binds, then a conformational change takes place
Does the alpha subunit have it’s own lipid anchor?
yes
What is a protein kinase?
enzyme that adds a phosphate
What is a phosphatase?
enzyme that removes a phosphate from a protein
What is a common way to change the activity of a protein?
phosphorylation
What are the 2 classes of kinases?
serine/threonine and tyrosine kinases
Where does kinases get the phosphate from?
ATP
Why are there regulator?
Turns off signal transduction pathway, if there is always a high signal it defeats the purpose of a signal
What are the 3 types of target proteins for protein kinases?
enzymes, ion channels, regulatory proteins
What is a kinase cascade?
each kinase catalyzes phosphorylation of another
What is the last part in the kinase cascade?
target protein
Does the kinase donate its phosphate to the substrate?
NOOO
What is cyclic AMP (cAMP)?
second messenger that is smaller and water-soluble
What are two different pathways that use cAMP?
epinephrine and glucogon
What is the effector that produces cAMP?
enzyme adenylyl cyclase
What does adenylyl cyclase do?
converts ATP to cAMP
What does the first pathway of G-proteins involve?
cAMP
What does the second pathway of G-proteins involve?
inositol triphosphate (IP3) and diacylglycerol (DAG)
Which second messenger sits in the membrane?
diacylglycerol (DAG)
Does diacylglycerol (DAG) float around in the cytosol?
no
What is the effector for the second pathway?
phospholipase C
How does phospholipase C work?
breaks down membrane phospholipid
What role can cAMP play in plants?
germination and some plant defensive rsponses
What does cAMP do?
control uptake and oxidation of glucose, glycogen breakdown or synthesis, ion transport, transport of aminos acid, and cell division
What is an example of cAMP?
Glucagon triggers a cAMP receptor–response
pathway in liver cells, which stimulates them to break
down glycogen into glucose units
What is IP3?
small, water-soluble molecule that diffuses rapidly
through the cytoplasm
Is DAG is hydrophobic? If so what does this mean?
Yes, this means it remains in the plasma membrane
Is DAG is hydrophobic? If so what does this mean?
Yes, this means it remains in the plasma membrane
Where does IP3/DAG second messenger pathway occurs?
all eukaryotic organisms
What does the IP3/DAG second messenger pathway do?
y control responses such as sugar and ion transport,
glucose oxidation, cell growth and division, and
movements such as smooth muscle contraction
What does the IP3/DAG second messenger pathway do in animal cells?
IP3 activates transport proteins in the ER that release stored Ca2+ into the cytoplasm – Ca2+, alone or with DAG, activates a protein kinase cascade that brings about the cellular effect
Do glucagon and epinephrine produce the same effect?
yes
What do glucagon and epinephrine do?
stimulate liver cells to mobilize glucose
Do glucagon and epinephrine act by the same signal transduction pathway?
yes
Is there a nuclear membrane for bacteria?
no
What is quorum sensing?
bacteria release signal molecules in increasing concentration as cell density increases, all cells then respond—-bacteria live in a quorum (community)
Do prokaryotes have the details/complexity of protein cascade?
no
What is an example of convergence?
Glucagon and epinephrine both come from adenylyl cyclase —-> cAMP
More enzymes and kinases leads to what?
more amplification
Where are IP2/DAG second messenger pathways universal among?
eukaryotic organisms
Where are IP2/DAG second messenger pathways control?
sugar and ion transport, glucose oxidation, cell growth and division, and movements such as smooth muscle contraction
What did Earl Sutherland do?
investigated how the hormone epinephrine activates the enzyme glycogen phosphorylase to catalyze the breakdown of glycogen in the liver
What was the significance of Earl Sutherland’s experiment?
Demonstrated that enzyme activation did not directly involve epinephrine (the first messenger in the system) but required another cellular factor (the second messenger)
—discovered second messenger
What are the 2 components in bacterial signaling?
1) surface receptor protein
2) intracellular response regulator
What are the steps in bacterial signaling?
1) A signaling molecule binds to and activates the surface receptor
2) Surface receptor phosphorylates and activates response regulator
3) Response regulator binds to regulatory sequences in DNA, which turns genes on or off
What is the evolution of cell communication?
1) mechanisms for cell signaling existed in unicellular organisms
2) quorum sensing in bacteria uses signal molecules in response to changes in it’s environment
3) unicellular eukaryote, yeast, use of signal molecules in mating
4) Some protein components of cell communication pathways are found in both prokaryotes and eukaryote
Where are protein kinases found?
after the evolution of eukaryotes
What is a pathway common to fruit flies and human? significance?
cell growth pathway, pathways is at least 800 million years old and supports evolution of cell communication.
What is the pathway of cAMP?
1) cAMP activates PKA
2) active PKA activates GPK
3) active GPK activates glycogen phosphorylase
