ch. 9 cell communication Flashcards
what two things are required for communication between cells?
a ligand and a receptor
what is a ligand?
a signaling molecule
what is a receptor?
a protein to which the ligand binds
where are receptors located?
may be on the plasma membrane or within the cell
what are the four basic mechanisms for cellular communication?
- direct contact
- paracrine signaling
- endocrine signaling
- synaptic signaling
what is direct contact?
when ligand molecules on the surface of one cell are recognized by receptor molecules on an adjacent cell
what is paracrine signaling?
when ligands released from a secretory cell bind to receptors on adjacent cells.
what is endocrine signaling?
when special ligands called hormones are released from secretory cells and bind to receptors on or within cells throughout the body
what is synaptic signaling?
when nerve cells release the signal ligands (neurotransmitters) which binds to receptors on nearby nerve or muscle cells.
what happens when a ligand binds to a receptor?
the cell “responds” chemically
what is signal transduction?
the series of chemical reactions that occur following the binding of a ligand to a receptor
what can different cell types respond differently to?
the same signaling ligand
what does signal transduction often involve?
activating or inactivating proteins
what is kinase?
an enzyme that adds a phosphate to a protein, thus activating it
what is phosphatase?
an enzyme that removes a phosphate from a protein, thus deactivating it
what happens during protein phosphorylation?
a phosphate group (PO4-3 ) is added by a kinase to residues of the amino acids serine, threonine, and tyrosine. This can activate the protein.
what are the two receptor locations?
cell surface and inside the cell
what is an intracellular receptor?
a receptor located inside the cell
what are the three classes of membrane receptors?
- channel linked/gated receptors
- enzymatic receptors
- G protein-coupled receptors
what are Channel linked or gated receptors?
class of membrane receptor where an ion channel opens in response to ligand binding
when do receptors fall into the enzymatic class?
when the receptor is an enzyme that is activated by ligand binding
what happens with G protein-coupled receptors?
a G-protein (protein bound to GTP) assists in transmitting the signal
what is receptor tyrosine kinase?
an enzyme receptor
what happens to the membrane bound receptor when signal ligand binds?
it is dimerized and autophosphorylated- activated receptor then adds a phosphate to tyrosine on a response protein
what is an example of receptor tyrosine kinase signaling?
epidermal growth factor receptor
what is a kinase cascade?
a series of protein kinases that phosphorylate each other in succession, amplifing the signal
what is the purpose of a kinase cascade?
So, a few signal ligand molecules can elicit a large cell response
what is a G protein?
protein bound to GTP
what is a G protein coupled receptor?
receptors bound to G proteins
_________ is a switch turned on by the ________.
G protein; G protein coupled receptor
when a signal ligand binds receptor, what does G-protein activate?
an effector protein
what can activate effector proteins?
G-protein coupled receptors
what does the effector protein produce once activated?
a second messenger
what does a second messenger do?
generates the cellular response
what is an example of a common effector protein?
adenylyl cyclase
what does adenylyl cyclase do?
converts ATP to cAMP, which then acts as a second messenger
what is the function of a cyclic AMP?
serves as a second messenger to activate or inactivate proteins
are steroid hormones polar or non-polar?
non-polar/lipid soluble
why are steroid hormones nonpolar?
so that they can cross the plasma membrane to a steroid receptor
what is the function of steroid hormones?
Usually regulate gene expression: an inhibitor blocks the steroid receptor from binding to DNA until the hormone is present.
what are the three functional domains of a steroid receptor?
- Hormone-binding domain
- DNA binding domain
- Domain that interacts with coactivators to affect gene expression (activating or deactivating transcription)
what are autoinducers?
small molecules produced by bacteria that regulate gene expression
what type of receptor are steroid hormones?
intracellular
