Cell Signaling Flashcards
(21 cards)
What type of cell signaling is long range and uses hormones as signals?
endocrine
Endocrine signaling is a long-range type of cell–cell signaling that uses hormones secreted in the blood by specialized cells. This is distinguished from paracrine signaling, which also uses chemical signals that are secreted but over a shorter range.
What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute?
one that involves a change in gene expression
Cell responses that include molecular events like the release of vesicles and firing action potentials are rapid. Cell responses that require changes to gene expression take time because the gene must be transcribed and translated before the effect is observed.
The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is
binding of the signal molecule to a receptor.
Signaling pathways that are activated in response to an extracellular signal must begin with the signal molecule binding to the receptor, often a membrane protein. Then the signal can be relayed and amplified inside the cell to produce cellular responses like activation of growth, gene expression, etc.
What describes negative feedback regulation?
A component late in the pathway inhibits an enzyme early in the pathway.
Negative feedback is when a product of a signaling pathway inhibits steps earlier in the pathway. This leads to a dampening of the response in response to strong activation. Hence, negative feedback can help a pathway switch rapidly between on and off states.
Enzymes that add a phosphate group to a switch protein are called
kinases.
Enzymes called kinases add a phosphate to a protein; the phosphate could either activate or inactivate the protein, depending on the protein. Phosphatases remove phosphates.
One of the two types of GTP-binding proteins, often called G-proteins, are membrane bound. These are the
trimeric GTP-binding proteins.
Trimeric GTP-binding proteins are often called G-proteins, and are membrane bound. These are distinct from the monomeric GTP-binding proteins, which are soluble proteins.
The active form of a monomeric GTP-binding protein is the
GTP-bound form.
Monomeric GTP-binding proteins (also known as monomeric GTPases) are in their active form when bound to GTP. An enzyme called GEF helps activate the GTP-binding protein by promoting its binding to GTP.
Which type of cell-surface receptor(s), when activated, catalyze(s) a reaction inside the cell?
enzyme-coupled receptors
When bound to a signal, enzyme-coupled receptors become active enzymes that catalyze a reaction inside the cell. G-protein-coupled receptors activate G-proteins, which can activate enzymes but do so indirectly.
When activated, a G-protein has a structure that
is bound to GTP.
G-proteins are heterotrimers, made up of an alpha, a beta, and a gamma subunit. When activated, the alpha subunit binds to GTP and dissociates from the rest of complex.
What produces the fastest response to G-protein activation?
ion channel activation
G-proteins can activate membrane-bound enzymes to produce second messenger molecules like cAMP and cGMP, or they can activate ion channels directly. Ion-channel activation is a rapid response that causes an immediate change in the cell, whereas small-molecule second messengers take longer to produce cellular outcomes.
What correctly matches a G-protein-activated enzyme with the second messenger molecule it produces?
phospholipase C à diacylglycerol
G-proteins activate membrane-bound enzymes like phospholipase C, which cleaves inositol phospholipids to produce the second messengers inositol triphosphate and diacylglycerol. Other important enzymes are adenylyl cyclase and guanylyl cyclase, which produce cyclic AMP and cyclic GMP, respectively.
Which cAMP-mediated signaling pathway would take on the order of minutes to hours for a response to develop (as opposed to seconds)?
a response where cAMP leads to the activation of a transcriptional regulator
Signaling pathways that lead to changes in gene expression via transcriptional regulators are slower and take minutes to hours for an effect. This is in contrast to signaling pathways that change protein activity or ion channel activity, which elicit changes in seconds to minutes.
Calcium ion release triggers all of the following biological processes
muscle contraction
fertilized egg development
secretion of neurotransmitters
What depicts the correct order of steps involved in nitric oxide (NO) signaling to trigger smooth muscle relaxation?
acetylcholine receptor activation à activation of NO synthetase à NO diffusion into neighboring cells à activation of guanylyl cyclase à cGMP production
In the smooth-muscle-relaxation signaling pathway, acetylcholine receptors in endothelial cells are activated by acetylcholine, activating a G-protein-signaling cascade leading to NO synthetase activation and production of NO, which diffuses into smooth muscle cells to activate guanylyl cyclase for cGMP production.
How does the binding of a signal molecule activate an RTK for downstream signaling?
The RTK forms a dimer and cross-phosphorylates itself.
RTKs are single transmembrane proteins that dimerize upon signal binding. The dimerization brings the kinase domains in close proximity to each other, allowing the two monomers to phosphorylate each other in a crosswise manner.
Which of the following is NOT an intracellular signaling protein activated by an RTK?
G-protein
Activated RTKs can stimulate Ras and other monomeric GTPases, as well as PI-3-kinase activity. G-proteins are stimulated by GPCRs.
If Ras contains a mutation that leads to a defect in GTP hydrolysis, this could fuel uncontrolled proliferation in cancer because
Ras is able to signal to downstream pathways inappropriately.
Mutations in Ras that allow Ras to remain in its active GTP-bound state for a longer amount of time will fuel inappropriate growth due to the prolonged signaling to downstream pathways involved in cell growth and proliferation.
Steroid hormones trigger transcription of target genes by
binding to nuclear receptors that act as transcription factors for specific genes.
Steroid hormones can pass through the plasma membrane and bind to nuclear receptors that act as transcription factors. Each steroid hormone binds to a different receptor, and the activated receptors bind to specific sets of genes to activate their transcription.
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________.
hormone
The following happens when a G-protein-coupled receptor activates a G protein.
The α subunit exchanges its bound GDP for GTP.
A protein kinase can act as an integrating device in signaling if it ___________________.
is activated by two or more proteins in different signaling pathways.
