Chapter 11 Flashcards
What is quorum sensing?
Concentration of signaling molecules allows bacteria to sense local population density
What is biofilm?
An aggregation of bacterial cells adhered to a surface
Types of local signaling
Paracrine signaling ; synaptic signaling
Paracrine signaling
Animal cells communicate using secreted messenger molecules that travel only short distances
Synaptic signaling
Occurs in the animal nervous system when a neurotransmitter is released in response to an electric signal
Long-distance signaling
Used hormones ; endocrine signaling (bloodstream)
Three stages of cell signaling
Signal reception, signal transduction, cellular response
Signal reception
Binding of ligand (signaling molecule) and receptor
Cell surface receptors
Membrane receptors located on cell surface ; heir large or polar ligands can’t diffuse through the membrane
Intracellular receptor
Located inside cell ; their ligands are small or nonpolar and can diffuse across the membrane
GPCRs
G Protein-coupled receptors
RTKs
Receptor tyrosine kinases
Receptor tyrosine kinases
Membrane receptors that transfer phosphate groups from ATP to another protein
Ion channel receptors (ligand-gates)
Contain a region that can act as a gate, opening or closing the channel, when the receptor changes shape
Intracellular receptors
Receptor proteins found in cytoplasm or nucleus
What can activated hormone-receptor complexes do?
They can act as a transcription factor, turning on or off specific genes
What is phosphorylation?
Protein kinases transfers phosphates from ATP to protein
Examples of second messengers
Cyclic AMP and Ca 2+ (spread by diffusion)
What does adenylyl cyclase do?
Converts ATP to cAMP in response to an extracellular signal
What does cAMP do?
Activates protein kinase A which then phosphorylates various other proteins
What does adenylyl cyclase do?
Makes cAMP from ATP
What happens in cholera bacterium?
Vibrio cholerae produces a toxin that modifies G proteins so that it is stuck in its active form ; leads to continuous production of cAMP, causing intestinal cells to secrete lots of salt which is fallowed by water ; untreated the person can die
Why is Ca 2+ a good second messenger?
It’s concentration in the cytosol is normally much lower than the concentration outside the cells and in certain organelles within the cell ; small change in # represents larger % change
IP3 & DAG and where they are produced
Inositol triphosphate & diacylglycerol ; produced by cleavage of a certain kind of phospholipid in the plasma membrane
4 aspects of signal regulation
Amplification of signal, specificity of response, overall efficiency of response, termination of signal
What happens in Signal amplification?
At each step the number of activated products can be greater than the proceeding step
What is specificity of cell signaling?
Proteins allow cells to detect and respond to different signals ; same signal can have different effects with different proteins
What is a scaffolding protein?
Large relay protein to which several other relay proteins are attached ; increase efficiency by grouping together different proteins involved in same pathway
4 ways to shut off signal
Ligand unbinds from receptor ; ligand/receptor complex is internalized and degrades ; second messengers are degraded ; protein phosphates remove phosphate off previously phosphorylated proteins
