AAAAAAAA Flashcards
conversion of an impulse or stimulus from one physical or chemical form to another. Also is the process by which a cell responds to an extracellular signal
Signal transduction
Communication between cells involves four essential elemnts
- signaling cell
- signaling molecule
- Target cell
- Receptor molecule
In intracellular communication signal is recieved by _______. It uses ________ messengers
receptors; second
a. Proteins or peptides
b. Amino acids or nucleotides
c. Steroids and fatty acid derivatives
d. Dissolved gases
Are all examples of what?
extracellular signal molecules
What are the 3 modes of signaling and the 1 mode of long distance signaling?
Short term:
(NPC) Neuronal, paracrine, contact-dependant;
Long term:
Endocrine
Endocrine signaling is _____ term and its signaling molecules are called _______. These are produced in endocrine glands.
long; hormones
pancreas produces insulin which regulates glucose uptake. This is an example of what type of signaling?
Endocrine
A type of local signaling. Signaling molecules released by one cell into the extracellular fluid act as local mediators. Signals act on neighboring target cells.
Paracrine Signaling
These are examples of what kind of signaling?
Growth factors – regulate growth and proliferation
Cytokines - molecules that regulate inflammation
Paracrine signaling
Type of Local signaling. Cells respond to signaling molecules that they themselves produce.
Example: Cancer cells
Autocrine signaling
Type of Local Signaling. Neuronal signals are transmitted electrically along a nerve cell axon.
Results in the release of neurotransmitters onto adjacent target cells. Message delivered quickly and specifically
Neuronal signaling
Involves direct contact between neighboring cells.
Cell-surface-bound signal molecule binds to a receptor protein on an adjacent cell.
Contact-Dependent Signaling
Insulin, Acetocholyine, EGF, and Delta are all examples of what?
signal molecules.
______ may be located on the cell surface or inside the cell.
receptors
_________ receptors bind extracellular signal molecules
Cell-surface receptors
Most Extracellular Signal Molecules are ______ and _____.
large; hydrophilic
These receptors are located in in the cytosol or in the nucleus. They respond to small hydrophobic signal molecules that can diffuse across the plasma membrane
Intracellular receptors
Steroid hormones are examples of small hydrophobic signal molecules that would bind to _______ receptors to regulate gene transcription or other functions
intracellular
Cells of multicellular organism encounter hundreds of different signaling molecules, but cells must respond to correct signal. The responding cell must express specific ________
receptor
T/F: A cell’s response to a signal can be fast or slow
true
In this type of cell response/signal, the signal affects the activity of protein already present inside the cell
Example: contraction of muscle cells
Fast signals
In this type of cell response/signal, the response requires changes in gene expression and production of new proteins
Examples: cell growth, cell division
Slow signals
Cell-surface ________ relay extracellular signals via intracellular signaling pathways.
Intracellular signaling molecules interact with specific ______ proteins. These change the behavior of the target cell
receptors; effector
T/F: Effector proteins change the behavior of the target cell
true
_______________:
-Relay signal
-Amplify signal
-Integrate signal: Detect signal from more than one signaling pathway
Distribute signal
Modulate signal via feedback
Intracellular signaling proteins
T/F: Feedback only occurs in specific parts of the signaling pathway
false, Feedback can occur anywhere along signaling pathway
Feedback can be _______ or _______
positive; negative
Molecular switches are ______ proteins. The receipt of signal causes them to toggle between ______ and _______ state.
effector; active; inactive
There are different classes of Molecular Switches.
Switches regulated by __________, such as protein ____________ and protein _______.
Phosphorylation; protein kinases; protein phosphates
Phosphorylation Cascade
Many switch proteins are themselves kinases.
yea
Molecular switches:
____________: activate when bound to GTP. It switches itself off by hydrolyzing its bound GTP to GDP
GTP-binding protein
Types of GTP-binding proteins:
_________proteins- relay messages from G-proteins coupled receptors.
________________- their activity is controlled by two types of regulatory proteins
Trimeric GTP-binding proteins; Monomeric GTPases.
The activity of Monomeric GTPases is controlled by two types of regulatory proteins: _____ & ______
GEF; GAP
T/F: GEF switches the protein off and GAP switches the protein on
false GEF on, GAP off
Cell-surface receptors fall into three main classes
_________ receptors
_________ receptors
_________receptors
Ion-channel-coupled; G-protein-coupled; enzyme-coupled
This type of receptor changes the permeability of the membrane to a specific ion and leads to change in membrane potential
Ion-channel-coupled receptors
This type of receptor activates membrane-bound G-protein. G-proteins like trimeric proteins initiate intracellular signaling cascade (activate or inhibit enzyme or ion channel in the plasma membrane)
G-protein-coupled receptors
These receptors act as enzymes to activate intracellular signaling pathways. They associate with enzymes that activate intracellular signaling pathways.
Enzyme-coupled receptors
T/F: Same extracellular signaling molecule can act on more than one type of receptor
true
These receptors are responsible for rapid transmission of signal across synapse. They convert chemical signals (neurotransmitter) into electrical signals (change in membrane potential).
Ion-channel-coupled receptors
T/F: G-protein-coupled receptors (GPCR) are the largest family of cell surface receptors
true
GPCRs associate with intracellular _____________. They mediate response to diverse extracellular signals
trimeric G proteins
GPCR Structure:
______(single/double) polypeptide chain
Is embedded in membrane
Has seven transmembrane ________
Single; alpha helices
Ligand binding causes what change in GPCR? And activates what?
causes conformational change in GPCR
Leads to activation of G protein
T/F: Several varieties of G-proteins share similar structure & mode of operation
true
In G-protein subunits the alpha and y subunits are tethered to membrane by _______.
However, the alpha subunit binds GDP/GTP.
GDP bound is ______
GTP bound is ______
lipid tail; inactive; active
Stimulation of GPCRs activates G-protein subunits.
-Conformational change of GPRC leads to conformation change of __________
g protein
Alpha subunit exchanges GDP for ____
- _____ required
- GTP binding leads to more conformational changes
GTP; GEF
Diverse signal molecules activate ______
- Proteins
- Small peptides
- Derivatives of amino acids
- Derivatives of fatty acids
GPCR
G protein activity:
An activated ________ interacts with its target protein. Target protein is activated (in this example). α subunit hydrolyzes bound GTP to GDP.
Activated By complex interacts with its target protein and inactive subunits reassemble.
α subunit
Some bacterial toxins cause disease by altering the activity of G Proteins
Examples are: _________toxin & _______ toxin.
Cholera ; Pertussis
T/F: Some G proteins directly regulate ion channels
true
Some G proteins directly regulate ion channels. Opening of ions channels causes immediate effect.
Example: heart pacemaker cells
Acetylcholine binds to GPCR which leads to activation of the Gprotein, G1. The activated βγ complex directly opens a K+ channel.
RESULT
Increased membrane permeability to ____ .
Also, makes membrane harder to activate and slows the heart rate
K+;
Many G proteins activate _____________.
Less rapid and more complex consequences.
Membrane-bound enzymes produce ____________ (aka
second messengers) which spread throughout a cell by diffusion. They then bind to specific signaling proteins in the cell and influence their activity.
membrane-bound enzymes; small messenger molecules
T/F: Cyclic AMP (cAMP) and Calcium ions are small messenger molecules
true
________:
Its an enzyme in the plasma membrane
One of the most frequent enzyme target for G proteins
Converts ATP to cAMP
Adenylyl cyclase
__________:
It converts cAMP to AMP
This terminates the cAMP signal
cAMP phosphodiesterase
cAMP usually activates AMP-dependent protein kinase (PKA).
cAMP binds to regulatory subunit of PKA releasing catalytic subunit.
Catalytic subunit of ______ phosphorylates various other proteins
PKA
In response to an extracellular signal, cAMP rises rapidly.
true
T/F: Epinephrin (aka adrenaline) binds to the GPCR adrenergic receptor.
true
Epinephrine stimulates _________ breakdown in skeletal muscle cells.
Increase in cyclic AMP activates ______
PKA phosphorylates and activates an enzyme called _________________
Phosphorylase kinase activates glycogen phosphorylase, the enzyme that breaks down glycogen.
glycogen; PKA; phosphorylase kinase
A rise in intracellular cyclic AMP can activate __________.
Activated PKA can enter the nucleus and phosphorylate specific transcription regulators
gene transcription
______________:
It’s one of the most frequent enzyme target for G proteins
Membrane bound enzyme.
Cleaves phospholipid – inositol phospholipoid
Generates second messengers IP3 and DAG
Phospholipase C
Phospholipase C cleaves a phospholipid called_____________.
And generates second messengers ____ and ____
inositol phospholipoid; IP3; DAG
The “hat” on the Inositol Phospholipid is what?
the sugar inositol
Inositol phospholipid pathway triggers a rise in intracellular _______-
Ca2+
DAG in the membrane recruits protein kinase C (PKC).
PKC is activated by _____. PKC activates intracellular proteins.
Ca2;
The cell maintains _______(high/low) cytosolic levels of Ca2+.
A _________(increase/decrease) in cytosolic Ca2+ signal triggers many biological processes.
low; increase
T/F: Fertilization of an egg by a sperm triggers an decrease in cytosolic Ca2+ in the egg
false, increase
Effects of Ca2+ mostly indirect through Ca2+-responsive proteins such as __________ which changes shape once Ca2+ binds.
Calmodulin
CaM-kinases are activated by _________. They phosphorylate select proteins
calmodulin
A GPCR signaling pathway generates a ____________.
The dissolved gas carries a signal to adjacent cells
Amino acid arginine broken down into NO
NO activates an enzyme guanylyl cyclase
Cyclic GMP (second messenger)
dissolved gas
This is the largest class of enzyme-coupled receptors. The cytoplasmic domain functions as a tyrosine kinase after activation. Full activation requires: Ligand binding & Autophosphorylation
Receptor Tyrosine Kinases (RTKs)
RTKs Activatio:n
Binding of signal molecule leads to dimerization of RTK.
Dimerization leads to _______________on specific tyrosine residues
auto-phosphorylation
Recruitment of intracellular signaling complex
Phosphorylated tail serves as________.
docking site;
_____ domains allow proteins containing those domains to dock to phosphorylated tyrosine residues on other proteins
SH2
Activation of an _____ stimulates the assembly of an intracellular signaling complex
RTK
Terminating the signaling cascade:
Protein Tyrosine phosphatases (PTPs) will ____________ RTK and intracellular signaling proteins. Then Receptor endocytosis (Degradation, Recycling) occurs.
dephosphorylate; endocytosis
Most RTKs activate the monomeric GTPase _____
adaptor recruits a Ras guanine nucleotide exchange factor (Ras‑GEF). Activated Ras can activate a MAP-kinase.
Ras;
Ras activates a _______ signaling module. Which is a three-kinase signaling module. Final kinase MAP kinase
activates various effector proteins.
MAP-kinase
RTKs recruit and activate phosphoinositide 3-kinase (PI 3-Kinase) . PI 3-kinase _________ an inositol phospholipid to produce lipid docking sites in the plasma membrane
phosphorylates
Inositol phospholipid attracts intracellular signaling proteins.
______ is a protein kinase that is activated at the membrane by two other protein kinases. It’s
released from the plasma membrane after phosphorylation and phosphorylates various downstream proteins on specific S/T residues.
Akt (PKB)
Activated Akt promotes __________
AKT phosphorylates and inactivates ______.
Bad promotes apoptosis by binding to and inhibiting Bcl2. Phosphorylated Bad releases Bcl2 and
Bcl2 blocks apoptosis and promotes cell survival.
cell survival; Bad
Akt stimulates cells to grow in size by activating the S/T kinase ______.
Tor
Akt stimulates cells to grow in size by activating the S/T kinase Tor. Akt acts on a Tor inhibitor (turns inhibitor off). Activated Tor stimulates ___________ and inhibits protein degradation.
protein synthesis
Some receptors activate a fast track to the nucleus.
Example: Notch Signaling (contact dependant)
nerve-cell production in the fruit fly Drosophila. Delta is the signaling molecule and Notch is the receptor.
Contact
T/F: Delta is the signaling molecule and Notch is the receptor.
true
After Delta (signal molecule ) binds to Notch (receptor) a protease cleaves tail of Notch. The Notch tail then migrates to nuclease and _____ Notch-responsive genes.
activates
Intracellular receptor proteins are found in the _________ or ________ of target cells
cytoplasm; nucleus
Protein kinase networks: ______ information and
Control complex cell behaviors
Integrate
Can GTP-binding proteins act as molecular switches,
letting a cell know that a signal has been received?
yes
What determines the direction that cellulose microfibrils are laid down in the extracellular space of a plant cell?
orientation of microtubules on the cytoplasmic side of the plasma membrane
What feature of glycosaminoglycans (GAGs) allows the extracellular matrix in cartilage to resist compression?
The negative charges on GAGs attract sodium ions, which draw water into the extracellular matrix to
form a water-filled gel.
Which statement is true about stem cells?
A. They can divide for the lifetime of the organism.
B. They are terminally differentiated.
C. They are usually present in large numbers, especially in tissues that undergo rapid renewal.
D. They always divide asymmetrically, giving rise to two different daughter cells.
A. They can divide for the lifetime of the organism.
Which is true of induced pluripotent stem (iPS) cells?
A. They can be used to produce whole organs for transplantation.
B. They can be produced artificially using a single transcription regulator.
C. They behave like embryonic stem cells.
D. They are produced by nuclear transplantation.
E. They can be produced by incubating adult fibroblasts with Ca2+.
They behave like embryonic stem cells.
