Cell Communication Flashcards
Why is cell communication important?
It is important for cell death, cell division, specification, and mating in yeast.
What is Quorum Sensing
communication among bacteria, coordinates cell behaviors, signal is released and when it exceeds threshold concentration, signal reception and signal transduction cause gene expression.
What are the forms of intercellular signaling?
Contact dependent, paracine (neighbor, stimulation, tissue); autocrine (self stimulation), synaptic (neuronal), endocrine (hormones, blood)
Describe intracellular communication -
signal transduction occurs through kinases and phosphotases.
What is signal transduction?
conversion of one signal to another
What are ligands?
Molecules that stimulate a response in the target cell. Can be cell surface bound or hydrophobic and bind intracellular receptors.
What are morphogens?
An extracellular signaling molecule that causes cells to have different fates based on their level of exposure to the signal.
Where receptors located?
On the cell surface or intracellularly.
How do multiple signaling molecules regulate cells?
Combinations of signaling molecules are integrated to control cellular processes. Same signal does not equal the same cellular decision in every cell type.
What causes one signaling molecule to have varied responses?
Different receptors and different intracellular signals.
Describe speed of response in endocrine and synaptic signaling.
Endocrine signaling has a slow response diffusing in blood. The ligand acts in low concentrations and the receptor has a high affinity for it.
In synaptic signaling, the response is rapid, the ligand is in high concentrations and the receptor has a low affinity for it.
What’s the difference between signals that alter protein function and those that use transcription and translation to alter protein synthesis?
Altering protein function is quicker.
What do protein kinase and protein phosphatase do?
Protein kinase adds a phosphate group through conversion of ATP to ADP. Protein phosphatase causes removal of phosphate group.
What causes a signaling molecule to be on or off?
GTP bound molecules are on, GDP bound molecules are off.
What are the types of cell surface receptors?
Ion channel coupled receptors, G-protein-coupled receptors, and Enzymes coupled receptors.
What are g protein coupled receptors?
Signal molecules are Molecules for taste and smell, Neurotransmitters, Hormones, Light.
Receptors have 7 pass transmembrane proteins, use trimeric or monomeric (ran, rho, rac, ras) g proteins to relay signal.
Describe trimeric G proteins -
Anchored in the cytoplasmic face of plasma membrane by lipids. • Composed of 3 subunits • GDP bound = Inactive • GTP bound = Active
Describe activation of g protein -
• Activated GPCR functions like GEF to drive exchange of GTP for GDP on G protein.
*GTP activates the A subunit.
• One GPCR can activate many G proteins.
• Activation results in conformational changes that allow interaction of α subunit and βγ complex with targets.
. • Hydrolysis of GTP by α subunit returns G protein to inactive state. (Helped by GAP)
What does adenylyl cyclase do?
It is an effector enzyme activated by 1 G protein. Stimulatory g proteins activate it, and inhibitory g proteins inhibit adenylyl cyclase.
Adenylyl cyclase catalyzes the production of cyclic AMP from ATP. cAMP activates protein kinase A.
What does cAMP do?
Produced from ATP using adenylyl cyclase.
It is a second messenger and a small intracellular mediator formed/released in response to an extracellular signal.
It relays signaling in the cell. cAMP phosphodiesterase destroys cAMP to stop signaling.
What is pKA?
PKA: cAMP-dependent protein kinase
• Composed of 2 regulatory and 2 catalytic subunits •cAMP binding to regulatory subunits causes conformational change and activation of catalytic subunits
Describe CREB -
phosphorylation by pKA activates it, causing it to bind to CBP and activate the target gene, resulting in gene transcription.
Describe amplification:
Amplification of a signal can occur at many points in a signaling pathway. Enzyme catalyzed steps are amplification steps.
Describe desensitization to signals.
Altered ability of a cell to respond to a stimulus over time. Results in pathway turning off.
