Chapter Nine: Cell Communication Flashcards
Cell signaling involves both ___________ and ___________ signals
incoming and outgoing
Any agent that can influence the properties of cells
A Signal
Signals are recognized by…
Receptors
What are allosteric and cause a cellular response?
Receptors
What type of signaling?
- cell junctions may allow signals to pass directly between cells
- Gap junctions would be an example
Direct Intercellular Signaling
What type of Signaling?
One cell has a membrane-bound signal recognized by a receptor by a receptor on another cell
Contact-dependent Signaling
What type of Signaling?
Cell Secretes a signal/chemical that bind to receptors on their own surface and that of neighboring cells of the same type, stimulating them
Autocrine Signaling
What type of signaling?
Cell Secretes a signal that influences not themselves but target cells in close proximity
Paracrine Signaling
What type of cell signaling?
Cell secretes a hormone into bloodstream that affects cells far from the source of the signal
Endocrine Signals
What are the three step response to signals?
- Receptor Activation
- Signal Transduction
- Cellular Response
The _________ ____________ binds to the Receptor causing a conformational change in the Receptor which activates its function
signaling molecule
Most signals are ______________ and can not enter cells through the membrane
hydrophilic
The initial signal is converted to a second signal _____________ the cell
inside
Many signals activate _____________ inside the cell
enzymes
Some signals alter the ___________ of structural proteins in the cell
function
Some signals affect _________ that bind to and regulate the activity of genes directly
proteins
What are signals that bind non-covalently and temporarily to Receptors?
Ligands
What changes the receptor to activate the ability to initiate the cellular response?
binding
Is binding temporary and reversible?
yes
When the _________ is released, receptor is no longer activated
ligand
The signal, often a _____________, binds the receptor
hormone
Receptors have different ______________ for the signal
affinities (preferences)
The Dissociation Constant (___) indicates the affinity
Kd
A low Kd indicates a ________ affinity
high
Receptors are necessary because most signals are hydrophilic or large molecules that will not diffuse through the…
Plasma Membrane
Cells need _________ receptors to bind specific signals
surface
Enzyme-linked receptors have a receptor in the ____________ _________ where the signal, often a hormone, bonds
Extracellular matrix
The _______________ ____________ has a catalytic function
Intracellular Domain
When the Extracellular Domain is bound, the ________________ _____________ is activated
Intracellular Domain
Most Enzyme-linked receptors have a protein ____________ function in the intracellular domain
Kinase
When bound by a signal, the protein kinase will ______________ other proteins
phosphorylate
Protein Kinases ____________ a phosphate from ATP and attach it to a protein
remove
The phosphorylated protein is usually _____________ to cause a cellular response
activated
G Proteins are named for their ability to bind _______ as a substrate
GTP
The receptors typically have _____ transmembrane segments which embed it in the Plasma Membrane
7
G Proteins have what two subunits?
alpha and beta
When bound by a signal, the receptor’s intracellular domain causes the G protein to release _______ and bind ________
GDP
GTP
When bound to the GTP, the ___ subunit dissociates from the ____ subunit
alpha
beta
After the alpha subunit dissociates from the beta subunit, it is then _______ and free to initiate a cellular response
active
That alpha subunit splits GTP to GDP, which allows alpha to be bound by the beta subunit, ____________ the G protein, ending the cellular response
inactivating
When the signal (ligand) binds the receptor, it changes conformation and opens the channel for an _____ to flow
ion
Some signals are _________ (hormones) and pass through the Plasma Membrane
steroids
Do intracellular receptors require a second messenger?
no
Intracellular Receptors bind signal to cause a conformational change in the ____________, activating it
receptor
The active signal or receptor complex enters the __________ and binds specific genes to activate them
nucleus
What is a hormone that activates a Receptor Tyrosine Kinase?
Epidermal Growth Factor
What does the hormone EGF stimulate throughout the body?
Cell Division
Receptor Tyrosine Kinases are secreted by ________________ Cells into the blood and is carried throughout the body
Endocrine
Two Epidermal Growth Factors each bind a receptor, which binds and ________________ each other on tyrosine amino acids
phosphorylate
Receptor Tyrosine Kinases: the now activated receptor activates _______ which then binds and activates _______
Grb
Sos
Receptor Tyrosine Kinases: activated ______ causes Ras to release GDP and GTP bind, which activates Ras
Sos
Receptor Tyrosine Kinases: _____ is the first Kinase in an Enzyme cascade
Ras
Ras binds and phosphorylated Raf, which binds and phosphorylates…
Erk
Receptor Tyrosine Kinases: Erk then enters the Nucleus and phosphorylates ______________ factors like Myc and Fos
transcription
Receptor Tyrosine Kinases: They bind genes (maybe 100) which then produce ____________ that stimulate cell division
proteins
Since most signals can’t enter the cell, they depend on a ___________ ___________ to produce the cellular response
second messenger
Second Messengers typically produce quick and short ____________ responses
cellular
When G Protein Receptors activate G Proteins, the _______ subunit is freed up, in turn activates a variety of other proteins
alpha
One common enzyme activated by alpha subunits is…
Adenylyl Cyclase
Adenylyl Cyclase is a membrane-bound enzyme, attached to the interior of the…
Plasma Membrane
The function of Adenylyl Cyclase is to remove _________________ from ATP, producing cyclic AMP (cAMP)
pyrophosphate
cAMP is a common….
second messenger
One common effect of cAMP is to activate….(PKA)
Protein Kinase A
PKA has two Regulatory Subunits that repress the two Catalytic subunits which phosphorylate and activate other…
proteins
cAMP binds the ___________ subunits which frees them from the _____________ subunits
Regulatory
Catalytic
Once the Catalytic subunit is freed it is…
active
Active PKA uses PO4 groups from _______ to phosphorylate and activate other proteins, causing a cellular response
ATP
Second Messengers have _______ durations
short
Phosphodiesterase hydrolyses cAMP to ATP, removing it from the Regulatory subunits of…
PKA
The Regulatory subunits then rebind the _____________ subunits of PKA, inactivating them
Catalytic
When PKA is activated it phosphorylates Phosphorylase Kinase which activates Glycogen Phosphorylase, which cutes Glucose-Phosphate from _____________, making it available to muscles
Glycogen
PKA also phosphorylates Glycogen Synthase, inactivating it to promote ____________ breakdown rather than synthesis
Glycogen
G proteins can activate ___________ other than adenylyl cyclase
enzymes
_______ binds G Protein-coupled Receptor
Signal
Activated G Protein alpha subunit activates….
Phospholipids C
Phospholipase C cleaves Phospatidylinositol releasing Diacylglycerol and Inositol Phosphate (IP3), both of which are…
Second Messengers
IP3 will bind to a Ligand-gated Ca+ channel on the _____, opening the channel
ER
Ca+ is actively transported into the ER so when the channel opens, _____ flows out
Ca+
Ca+ is another __________ Messenger
Second
In conjunction with Diacylglycerol, Ca+ binds and activates…
Protein Kinase C
Ca+ by itself can also bind and activate the protein _____________, which in turn alters the function of still other cellular proteins
Calmodulin
Second messengers __________ the signal so that each successive step in the pathway produces more and more messengers
amplify
Second messengers are generally ________ and ______________
small and hydropholic
Second messengers being small and hydrophilic allows them to rapidly diffuse throughout the cell to produce a ________ response
quick
Hormones are chemicals secreted in minute quantities into the _______________ which have effects in distant parts of the body
bloodstream
Hormones can either be steroid and enter through _____________, or proteins and bind _____________ to produce a second messenger
membranes
receptors
Only cells with receptors for that hormone can respond to the _______________
hormone
Different receptors have different affinities for a hormone, so depending on the __________, some will respond and others will not
concentration
Different cells have different _______________ pathways, so respond differently
transduction
Different cell types may not express certain proteins, even if…
stimulated
Glycogen breakdown is under the influence of Epinephrine/Adrenaline which is the enzyme responsible for that ____________
breakdown
But if Glycogen Phosphorylase is not expressed in the cell there will be no response even if…
stimulated
Apoptosis is….
cellular death
The death of some cells during development is normal and helps form the ____________ of the body
organs
Cells experiencing extensive damage are programmed to die rather than damage other cells and the life of the whole….
organism
Intrinsic and Extrinsic signal transduction pathways lead to…
apoptosis
Internal damage, such as massive damage to DNA can produce ___________ signals leading to Apoptosis
internal
Surface proteins on the _______________ play a key role in this Intrinsic Pathway leading to Apoptosis
Mitochondria
________________ signals can also, through a different pathway, promote apoptosis
Extracellular
There are death receptors in the ______ ______________ of cells
cell membranes
When bound by a signal the death receptor initiates a cellular response leading to a programmed cell…
death
Apoptosis usually involves the activation of ______________ which destroy the cytoskeleton and Dnases which destroy the DNA
proteases
