Studied by 3 peopleCell to cell communication is critical for the ___ and __ of cells?
function and survival
What is cell to cell communication responsible for?
growth and devlopment of multicellular organisms
What are 3 ways cells communicate
Direct Contact
Local Signaling
Long Distance Signaling
Direct Contact
communication through cell junctions
What do signaling substances do?
Signaling substances and other material dissolved in the cytoplasm can pass freely between adjacent cells
Differentiate the different type of cells for direct contact for animals & plants
Animal cells- gap junctions
Plant cells- plasmodesmata
Example of Direct Contact
Immune cells;
Antigen presenting cells (APCs) communicate to T cells through direct contact
Local regulators
secreting cell will release chemical messages (local regulators/ligands) that travel a short distance through the extracellular fluid
In Local Regulation how do chemical messages work?
The chemical messages will cause a response in a target cell
Examples of Local Regulators
Paracrine signaling
Synaptic signaling
Paracrine signaling
secretory cells release local regulators (ie growth factors) via exocytosis to an adjacent cell
Where does Synaptic signaling occur?
Occurs in animal nervous systems
How does Synaptic signaling work?
Neurons secrete neurotransmitters
Diffuse across the synaptic cleft- space between the nerve cell and target cell
Long Distance Signaling
Animals and plants use hormones for log distance signaling
Describe Long Distance Signaling in Plants
Plants release hormones that travel in the plant vascular tissue (xylem and phloem) or through the air to reach target tissues
Describe Long Distance Signaling in Animals
use endocrine signaling
Specialized cells release hormones into the circulatory system where they reach target cells
Exampling of Long Distance Signaling
Insulin
Insulin is released by the pancreas into the bloodstream where it circulates through the body and binds to target cells
What are the 3 stages in cell to cell messaging?
Reception
Transduction
Response
Reception
1st step
ligand binds to receptor
Transduction
2nd step
signal is converted
Response
3rd step
A cell process is altered
Receptor
macromolecule that binds to a signal molecule (ligand)
All receptors have what?
An area that interacts with the ligand and an area that transmits a signal to another protein
Binding between ligand and receptors are considered to be?
highly specific
What happens to the receptor when the ligand binds to the receptor? What does this allow for and what is the result?
the receptor activates (via a conformational change)
Allows the receptor interact with other cellular molecules
Initiates transduction signal
Where are the 2 places receptors are found
Receptors can be in the plasma membrane or intracellular
Most common type of receptor involved in signal pathways?
Plasma Membrane Receptors
Where do plasma membrane receptors bind?
Binds to ligands that are
polar/water-soluble
and/or large
Examples of Plasma Membrane Receptors?
G protein coupled receptors (GPCRs)
Ligand-gated ion channels
Where are intracellular receptors found?
In the cytoplasm or nucleus of target cell
Where do Intracellular Receptors Bind?
Bind to ligands that can pass through the plasma membrane
Example of Intracellular Receptors
hydrophobic molecules
Steroid & Thyroid Hormones
Gasses like nitric oxide
What is converted in transduction? What is the result?
An extracellular to an intracellular signal
brings about a cellular response
What is required in Transduction?
Requires a sequence of changes in a series of molecules (signal transduction pathway)
What does the signal transduction pathway regulate?
Protein activity
Describe how signal transduction regulates protein activity
Phosphorylation by the enzyme protein kinase; relays signal inside cell
Dephosphorylation by the enzyme protein phosphatase; shuts off pathways
What occurs to the signal during transduction?
the signal is amplified
Second Messengers
small, non-protein molecules and ions that help relay the message and amplify the response
What is a common second messenger?
Cyclic AMP (cAMP)
Response
the final molecule in the signaling pathway
converts the signal to a response that will alter a cellular process
What does figure A represent?
An example of a response in cell signaling
A protein that can alter membrane permeability.
What does figure B represent?
An example of a response in cell signaling
An enzyme that will change a metabolic process
What does figure C represent?
An example of a response in cell signaling
A protein that turns genes on or off
What is the actual “signal” being transduced in a signal transduction pathway?
a ligand
How is the “signal” in a signal transduction pathway passed from outside to inside the cell?
Through transduction
during transduction the signal is relayed by protein kinases and amplified by second messengers
Signal transduction pathways can influence ___? What does it result in?
how a cell responds to its environment
They can result in changes in gene expression & cell function; can alter phenotypes or result in cell death
Mutations to receptor proteins or to any componet of the signaling pathway will result in?
a change to the transduction of the signal
What are the 2 main categories of cell membrane receptors in eukaryotic organisms
G protein coupled receptors (GPCRs) and Ion channels
G protein coupled receptors
largest category of cell surface receptors
important in animal sensory systems
binds to a G protein that can bind to GTP (an energy molecule)
The GPCR, enzyme, and G protein are inactive until?
ligand binding to GPCR on the extracellular side
What is the result of the ligand binding to GPCR?
Causes cytoplasmic side to change shape
allow for the G protein to bind to GPCR (activating the GPCR & G protein; GDP→ GTP)
After the G protein is activated where can it now bind? What are the results
to the enzyme
activates the enzyme → amplifies signal and leads to a cellular response
Ligand gated ion channels: Location, Importance, Definition.
Located in the plasma membrane
Important in the nervous system
Receptors that act as a “gate” for ions
What is the affect when a ligand binds to the receptor? In ligand gated ion channels
the “gate” opens/closes allowing the diffusion of specific ions
initiating a series of events that lead to a cellular response
Note
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