Communication Flashcards
There are 3 mechanisms for local signalling
Gap junction dependent communication
Contact dependent signals
Paracrine and autocrine
Explain gap junctions
Channels that connect adjacent cells
Water filled pore allows same molecules and ions to diffuse from one cell to the next
Cells are connected by cytoplasmic bridges
Two adjacent cells express channel proteins in gap junctions called ____
Connexins
What are common places for gap junctions
Common in heart smooth muscles and some neurons
Two ____ form a functional gap junction between two adjacent cells
Connexons
Each connexon is made of __ connexin monomers
6
Explain contact dependent signalling
A molecule (ligand) in the Extracellular matrix of one cell binds to a receptor in the membrane of the adjacent cell
What are common places for contact dependent signalling
Immune system
Development
Explain local communication
A signalling molecule is released
Paracrine - signalling to cells in the immediate vicinity
Autocrine - signalling to self
Signalling to self is what type of local communication
Autocrine
Signalling to cells in the immediate vacinity is what type of local communication
Paracrine
What’s an example of long distance communication
Endocrine system
Neurotransmitters
Neurohormones
What does the endocrine system do
Secretes hormones
Chemicals secreted into the blood that affect cells in other parts of the organism
What does endocrine refer to
The substance secreted in to the blood such as insulin
What does exocrine refer to
Substances secreted into a duct such as digestive enzymes from pancreas
Into pancreatic duct then digestive system
___ cells with ___ for the hormone responds to the signal sent out by the endocrine glands or cells
Target
Receptors
Explain neurotransmitters
An electrical signal travels distance along a nerve cell
Causes release of a chemical. The chemical travels across a small gap onto a target
Explain neurohormones
An electrical signal travels the distance along a nerve cell
Causes release of a chemical. The chemical is released into the blood and acts at distant targets
_____ are chemicals secreted by neurons that diffuse across a small gap to the target cell
Neurotransmitters
____ are chemicals released by neurons into the blood for action at distant targets
Neurohormones
Except for gap junction signalling
Cell to cell signalling requires what
Signal (ligand)
Receptor
Way to transduce the message intracellular signalling pathways
Explain how intracellular signal pathways are activated
Signal molecule binds to a receptor protein and ACTIVATES intracellular signal molecules which ALTERS target proteins to CREATE a response
Are intracellular signal pathways ubiquitous
Why are these important
All cells have some pathways
Only certain cells have specific pathways
Amplify signals
Two main categories of ligand receptor interaction
Based on receptor location
Intercellular receptors
Cell membrane receptors
Explain intracellular receptors
Ligands are usually lipophilic (hydrophobic)
Able to diffuse through cell membrane and bind to receptors in the nucleus of cytosol
Often alter gene expression (slow but long lasting)
Explain cell membrane receptors
Ligands are usually lipophibic (hydrophilic)
Ligand does not diffuse through cell membrane
Bind to membrane receptors
Cause intracellular cascade
Give example of lipophilic Ligands
Give example of lipophobic Ligands
Steroid hormones
Insulin and other peptide hormones
What are integrin receptor
Binding ligand stimulates changes in cytoskeleton
Cell movement growth and wound healing
Explain Receptor channels
Also known as an ion channel
Often called ligand gated ion channel
Neurotransmitter gated ion
Ionotropic receptors
The ligand is often a neurotransmitter
When the ligand binds the channel opens and allows ions to enter and leave cells (synaptic)
Allow Ca into cells (calcium is an important intracellular signal)
____ enzymes and ____ both activate amplifier enzymes
Receptor
G protein coupled receptor
On me ligand is amplified into ___ intracellular molecules
Many
Results in signal amplification are
A small amount of ligand creates a large effect
Tyrosine Kinase receptor
Transfers a phosphate group from ATP to a tyrosine residue (an amino acid) of a protein
Signal molecule binds to surface receptor the tyrosine kinase is on the cytoplasmic side and phosphorylated tyrosines on proteins
What is a specific example of TKR
Insulin receptor
Explain the insulin receptor
The alpha subunit binds insulin (which is the ligand)
Binding of insulin causes receptors to dimerize and autophosphorylate. The bets subunit transmits a signal from the bound insulin to the cytoplasm
The dimerization and autophosphorylation activate a kinase domain in the cytoplasm
Kinase domains on the the receptor phosphorylate insulin receptor substrate triggering other responses inside the cell
Explain the G protein coupled receptors
Hundreds of known GPCR
Also called metabotropic receptors
7 transmembrane domain receptor
Generate second messengers
Why are they called G proteins
Because they bind GDP and GTP
What is andenylyl cyclase
The amplifier enzyme that the G protein activates when it diffuses along the inside of the membrane
Each G protein activates ___ adenylyl Cyclase
One
In andenylyl cyclase the ligand binds to what and does what
G protein receptor
Activates the G protein
Once the G protein is activated in Andenylyl cyclase the G protein can _____ along the _____ of the membrane
Diffuse
Inside leaf
Adenylyl cyclase converts several hundred _____ into ____
ATP
cAMP
What is the second messenger in andenylyl cyclase and can diffuse throughout the cell
cAMP
cAMP activates _______
Protein kinase A
Protein kinase A diffuses within cell to ______ many other proteins
Phosphorylate
Many types of proteins can be phosphorylated giving rise to complex cellular responses
What are three examples of GPCR
Andenylyl cyclase
Phospholipase C
Arachadonic acid
What does PL - C stand for
Phospholipase C
What does DAG stand for
Diacylglycerol
What does PK C stand for
Protein kinase C
What does IP3 stand for
Inositol triphosphate
What does ER stand for
Endoplasmic reticulum
The the ligand binds and activates the G protein receptor it activates _____ which is the ____
Phospholipase C
The amplifier enzyme
PLC degrades membran phospholipids into two second messengers which are ___ and ___
Diacylglycerol
Inositol triphosphate
DAG stats associated with the ___
Lipid
IP3 is a small polar molecule that ____ through the ___
Diffuses
Cytoplasm
DAG activates ____
Protein kinase C
PLC diffuses within the cell and ____
Phosphorylates other proteins
IP3 binds to the ___ receptor on the ___
IP3
Endoplasmic reticulum
Activated IP3 receptor allows stores of __ to be released into the ___
Ca
Cytoplasm
When Ca is released into the cytoplasm it becomes ____
Another second messenger
What are the classic second messengers
cAMP
cGMP
IP3
DAG
What are the novel second messengers
Ca
Gasses
Lipids
Explain Ca as a second messenger
Binds the calcium binding protein calmldulin to activate other proteins
Binds to motor proteins and allows action of cytoskeleton and motor proteins
Binds to synaptic proteins to trigger exocytosis
Binds to ion channels to modulate their gating
In fertilized eggs initiates development
Ca binds to the calcium binding protein ___ to activate other proteins
Calmldulin
Explain gasses as second messengers
Soluble gasses are now being recognized as second messengers
NO (nitric oxide)
CO (carbon monoxide)
H2S (hydrogen sulfide)
CO activates ____
Guanylyl cyclase
NO is synthesized by ___
NO synthase
NO activates ____ and the production of cGMP leads to ____ of smooth muscles
Guanylyl cyclase
Relaxation
The arachadonic acid pathway is similar to the ____ pathway
PL-C
In arachadonic acid G proteins activate ____ which is the ____
Phospholipase A2
Amplifier enzyme
PLA2 degrades phospholipids into ___ which is an ___
Arachadonic acid
Eicosanoid
Arachadonic acid are ___ within a cell
And diffuse out of the cell and act as a ____ for GPCR cell membrane and adjacent cells
Second messengers
Ligand
Why does the hormone epinephrine (which is adrenaline) causes some blood vessels to constrict and others to dilate
The presence of receptor isoforms
Target response depends on the ___
Target receptor
Epinephrine can bind to different isoforms of the _____ receptor
Adrenergic
Epinephrine + alpha receptor =
Vessel constricts
Epinephrine + beta2 receptor =
Vessel dilates
Some Ligands can activate ___ receptors
Some receptors are activated by more then ___ ligand
Multiple
One
Alpha and beta 2 receptors may be activated by either ___ or ___
Epinephrine
Norepinephrine
Receptors can be ____regulated or ___regulated
What are examples
Up
Down
Development
Homeostatic challenges
Disease states
Receptors can be desensitized
Provide example
Phosphorylation of alpha and beta receptors can cause them to have lower affinity for Ligands
Mechanism of drug tolerance as a result continuous exposure to an agonist
Control pathways for homeostasis follow and ____
Response and feedback loops
Explain negative feedback
Initial stimulus To Response To DECREASED STIMULUS To response loop shuts off
Explain positive feedback
Initial stimulus To Response To increased stimulus To Positive feedback cycle back to the response
How do you shut off the positive feedback cycle
An outside factor is required
Negative feedback keeps system ___ a setpoint
Near
Negative feedback response acts to __ the stimulus
Negate
Negative feedback response can ____ homeostasis but cannot___ the initial perturbation
Restore
Prevent
Positive feedback brings a system _____ from a setpoint
Further
Positive feedback response acts to ____ the stimulus
Reinforce
What is the feed forward control
A small stimulus sets off a chain of events aimed at preventing a perturbation
Requires a complex program
Ie) mouth watering in anticipation of food (psychologists may disagree)
Neural control systems speed and specificity
Aimed at specific target
Fast acting
Shorter lived
Endocrine control systems speed and specificity
Target specificity determined by only receptors
Longer to act
Tends to last longer
