Copy of Unit 4 Cellular Communication & Cell Cycle 24-25 Flashcards
What is Cell Signaling?
Cell signaling is the series of steps that allow cells to respond to signals from their environment.
How do cells respond to accepting a cell signal?
Cells respond by initiating some sort of cellular activity, such as the initiation of the cell cycle.
What is a ligand?
A ligand is a chemical signal secreted from the initiating cell that travels to the target cell.
What determines a cell’s receptors ability to accept a signal?
Correct shape and charge.
Only cells that have the correct receptor protein will react to the signal molecule.
How do cells communicate?
Cells communicate by sending and receiving chemical messengers.
What is quorum sensing?
a process of cell communication that allows bacteria to share information based on high cell density and adjust gene expression accordingly. (Like bioluminescence in prokaryotes)
What role does adrenaline play in cell communication?
Secretion of the hormone adrenaline achieves cell communication in the fight-or-flight response.
What happens during the response step of cell signaling?
The final molecule in the signal pathway initiates transcription of target genes in the nucleus, leading to protein synthesis that causes the cell response.
What occurs during the basic transduction step?
Signal is moved from the cell membrane to the nucleus through phosphorylation of a series of proteins until the last one enters the nucleus
What occurs during the reception step? What happens to the receptor?
Ligand binds to the receptor, causing a conformational change that transmits the signal inside the cell.
What is paracrine signaling?
When the Communicating cell releases a signaling molecule (ligand) that moves to the target (receiving cell). along short or long distances by diffusion
How does endocrine signaling work?
Endocrine signaling takes place over long distances and relies on the circulatory system for transport of signaling molecules.
What is autocrine signaling?
Autocrine signaling occurs when a cell signals itself by sending a chemical messenger to its own receptor
(such as activated T-cells releasing interleukin-2 to stimulate their own proliferation.)
What are gap junctions?
Gap junctions occur in animal cells when the cell membrane of cells fuse and open pores between them.
This allows signals to quickly diffuse and initiate cell response.
What are plasmodesmata?
Plasmodesmata are plant cell-specific pores taht open between the cell membrane/wall of two cells.
allows signals to quickly diffuse and initiate cell response.
What is traditional cell-cell contact?
Traditional cell-cell contact involves an originating cell expressing a ligand on its membrane and a target cell expressing a receptor protein.
What is the difference between cell-to-cell signals and environmental signals?
Cell-to-cell signals are much more specific and intentional compared to environmental signals.
What are intracellular receptors? What type of ligands do they bind to?
Intracellular receptors are found in the cytosol and bind to lipid-soluble ligands that diffuse across the membrane and interact with genes in the nucleus.
This complex travels directly to the nucleus to initiate cell response bypassing transduction
What are membrane-bound receptors? Why type of ligands bind to them?
Hydrophillic ligands bind to a receptor that is embedded in the cell membrane. The ligands don’t cross the membrane.
Signal is amplified and moved from the membrane to the nucleus via a transduction pathway
What is the role of G protein-coupled receptors?
G protein-coupled receptors change conformation upon binding signals and trigger a signal transduction cascade.
What is the function of second messengers?
Second messengers amplify signals and drive response mechanisms in target cells.
What is the role of phosphatases in relation to second messengers?
Phosphatases deactivate second messengers like cAMP to terminate responses initiated by G protein-coupled receptors.
What are receptor-protein kinases?
Receptor-protein kinases have a signal-binding function and an enzyme function activated upon binding the signal. Responses initiated by them are terminated by the release of a signal
What are ligand-gated ion channels?
Ligand-gated ion channels are proteins that have signal binding and ion channels that can open or close to alter ion movements across the membrane, allowing rapid communication (ex in neurons.)
What do hydrophobic signaling molecules do?
Readily enter receptor proteins in cells that together can turn genes on or off by altering protein synthesis in the response pathway.
Whats an example of a hydrophobic signal?
Steroid hormones,
How do cells respond to signal transduction?
initiating transcription of target genes and producing proteins.
What are examples of cell responses?
Examples include initiation of gene expression, cell growth, secretion of molecules, and initiation of cell death.
What happens when there are mutations in signaling pathways?
Mutations can change or stop the cell response from occurring properly. It can also change chemical afffinity
How do medicines and toxins affect signaling pathways?
Many medicines and toxins work by activating or inhibiting signaling pathways.
Like paralysis causing neurotransmitters not to be released
What is an agonist?
An agonist stimulates a response in a target cell.
What is an antagonist?
An antagonist prevents a response in a target cell, even when the normal ligand is present.
How can genetic mutations affect signal transduction?
Mutations can interfere with the signal transduction pathway, affecting the cell’s responses.
What do membrane-bound receptors require to move the signal from the membrane to the nucleus?
Transduction
What happens when a ligand binds to a receptor?
The receptor changes shape, transmitting the signal into the cell
What is a second messenger in signal transduction?
A molecule that is activated, such as cyclic AMP, to phosphorylate the next protein in the chain
What does the activation of proteins in the signal transduction pathway lead to?
The activation of the last protein, usually a transcription factor, which enters the nucleus
Fill in the blank: A ligand binds to the receptor, causing it to change shape, which transmits the signal into the _______.
cell
True or False: The last protein in the signal transduction pathway is typically a transcription factor.
True
What is the role of cyclic AMP in the signal transduction process?
It acts as a second messenger that phosphorylates the next protein in the chain
What initiates the cell response after the signal transduction pathway is activated?
A transcription factor enters the nucleus
signal transduction step by step with a G protein (yes this is long)
Ligand binds to receptor causing it to change shape allowing a G protein with GDP to leave and a GTP to take it’s place. Then it uses G proteins on the membrane to trigger a signal transduction cascade by activating adenylyl Cyclase to convert ATP to cAMP, a secondary messenger. Many cAMP then phosphorylates the protein kinase activating it and it does do many times (this is the phosphorylation cascade). each kinase enzyme then phosphorylates many target proteins
signal transduction with a G protein after the ligand leaves the receptor
cAMP is deactivated by phosphatases to terminate response initiated by G protein-coupled receptors
what are the steps in Basic Transduction? (without a
G protein) p.s this is long
Ligand binds to membrane bound receptor which sends a signal and activates a protein. This protein then hands off the phosphate it got from cAMP until it reaches the last protein in the pathway (usually a transcription factor) enters the nucleus and initiates cell response.
Exactly what happens after a ligand leaves a receptor protein that had a G complex? - semi long answer
The protein conforms back to normal a the activated G protein deactivates itself by converting GTP to GDP. Then enzymes in the cytosol degrade cAMP, stopping the phosphorylation and activating of target proteins. (Now that there’s no cAMP, kinase can’t be activated and it can’t advocate any more proteins). Afterwards phosphotase removes phosphate groups from activated targeted proteins, inactivating them.
Identify 3 locations of cellular receptors
Membrane,cytosol,nucleus
Identify the properties of a ligand that has an intracellular receptor
Small (to get through membrane), hydrophobic, nonpolar
Identify the properties of a ligand that has an extra cellular receptor
Size of the membrane blind receptor, polar, hydrophilic
