CELL SIGNALING Part 1
10. Which enzyme plays a role in regulating rhodopsin-induced closing of cation channels? a. guanylyl cyclase b. adenylyl cyclase c. phosphodiesterase d a and c e. b and c
D
14. The activity of -adrenergic receptors is regulated by a. -adrenergic receptor kinase (BARK). b. clathrin. c. -arrestin. d. a and c e. all of the above
E
Cell sensitivity to an external signal is determined by 1.kon. 2.koff. 3.Kd. 4. the number of surface receptors.
4. the more receptors it has the more it can bind to cause downstream second messenger affects within the cel.
Vitamin D3 is synthesized in the skin by the sun but activated in the _____ and ______.
;liver and kindeys
11. Which of the following is a common step in the opening/closing of ion channels by acetylcholine and rhodopsin binding to their receptors? a. The G·GTP subunit dissociates from the G complex. b. The released G·GTP subunit interacts with the ion channel. c. The released G complex interacts with the ion channel. d. The released G·GTP subunit activates cGMP phosphodiesterase.
A
In paracrine signaling, the signaling molecule... a. acts on cells in close proximity to the secreting cell. b. acts on target cells far away from the secreting cell. c. acts on the same cells that secreted the signaling molecule. d. is carried to the target cells by the blood.
A. within the interstitum
An individual signalling molecule (ligand) can have different effects at different target cells. An example of this would be _______ that can bind to a heart pacemaker cell, salivary gland cell, and or a skeletal muscle cell. 1. Heart pacemaker: decrease the firing rate 2. Salivary Gland: stimulate secretion 3. Muscle: contraction
Acetycholine
Positive feed back occurs when.. a. Relatively rare b. limits cellular response to maintain stability c. response activates its source (to produce more) d. May be stopped by a definitive event (achieved its goal) acd. all 3 of these
Answer: ACD. after a cell is stimulated it will produce a product (response) that will then + activate the source ( the cell) to produce even more.
The difference between negative and positive feedback? Negative feed back occurs when.. a. response inhibits its source b. limits cellular response to maintain stability c. response activates its source ab. Both a and b
Answer: ab, once a stimulus stimulates a cell that cell will produce a response (product) and that product will then inhibit the source (the cell that produced it).
What type of cell signal is not only the synthesizing cell but also its own target cell? AKA it stimulates itself?
Autocrine
3 If [R] = the free receptor concentration and [L] = the free ligand concentration, Kd is a. [R]/[L]. b. [L]/[R]. c. [R][L]/[RL]. d. [RL]/[R] [L].
C.
8. All the following statement(s) about cholera toxin are true except a. It chemically modifies the Gs protein. b. It is a G protein-coupled receptor. c. It prevents hydrolysis of bound GTP to GDP. d. It leads to continuous activation of adenylyl cyclase.
B. Its NOT a G protein couple receptor ITSELF, it simply inhibits and activates certain components of the G protein.
12. Which of the following statement(s) about adenylyl cyclase stimulation/inhibition in adipose cells is (are) true? a. Prostaglandin E1 stimulates adenylyl cyclase. b. Glucagon inhibits adenylyl cyclase. c. Epinephrine stimulates adenylyl cyclase. d. b and c e. all of the above
C
Which of the following mechanisms can terminate the intracellular signaling pathway once the concentration of the external signal decreases? a. degradation of the second messenger b. desensitization of receptors c. deactivation of a signal transduction protein d. a and b e. all of the above
C you need a second messenger to be activated by an external hormone or ligand binding to the receptor and without that occurring you have deactivation of a signal transduction pathway (second messenger)
5. Which of the following is not a common intracellular second messenger a. inositol 1,4,5-trisphosphate (IP3) b. 1,2 diacylglycerol (DAG) c. adenosine triphosphate (ATP) d. 3´-5´ cyclic guanine monophosphate (cGMP)
C. All other are!
7. Which of the following general statement(s) about a G trimeric protein-coupled receptor is (are) true? a. It contains seven transmembrane domains. b. It is organized with the N-terminus on the cytoplasmic face of the membrane. c. It is organized with the C-terminus on the cytoplasmic face of the membrane. d. a and c e. all of the above
C. the cell is ALWAYS more + positive outside the cell and more - inside the cell. amino group NH3+ is + and carboxyl COO- is negative
16. Phosphatidylinositol 4,5-bisphosphate (PIP2) is cleaved by phospholipase C into ? a. 1,2-diacylglycerol (DAG). b. phosphatidylinositol (PI). c. inositol 1,4,5-trisphosphate (IP3). d. a and c e. all of the above
D.
20. After a meal, when blood glucose rises, circulating insulin binds to insulin receptors on various cell types and reduces blood glucose levels by a.fusion of intracellular vesicles containing GLUT4 glucose transporters with the plasma membrane. b.stimulation of the conversion of glucose to glycogen. c.inhibition of glucose synthesis from smaller molecules. d.all of the above
D.
Calmodulin a. is a ubiquitous protein in eukaryotic cells. b. binds Ca2+ in a cooperative fashion. c. is a membrane-bounded protein. d. a and b e. all of the above
D. its not membrane bound as its within the cytoplasm and activated by calcium from the SER of muscle cells. calcium-calmodulin THEN activates protein phosphorylase kinase to activated glycogen phosphorylase.
What time of cell signal secretes its hormones/molecules into the blood stream (no ducts) to act on distant target cells?
Endocrine (no ducts) exocrine contains ducts.
6. Phospholipase C is activated by a. Gas b. GaI c. Gaq d. Gao e. Both a and c f. Both c and d
F.
what is the term for an anticipatory effect in response to an EXPECTED stimulus? this can either be a negative expected stimulus or a positive expected stimulus. Example on back. Responses may be nervous (muscle stimulus, I feel) or endocrine (in the blood, releasing cortisol that you dont necessarily feel)
Feed Forward (premature) I am really excited for school to start TOMORROW (anticipatory). Feelings of happiness before the even (feed forward) Im dreading school to start tomorrow (anticipatory). feelings of shyness or anger (feed forward before it even happens).
The chemical messengers that travel throughout our blood stream and MOSTLY act on distant target cells are? through second messenegers inside the cell.
Hormones
famous for binding hormones like? involved in binding growth factors. IGF-1
Insulin
what type of hormones are small, and can diffuse across the plasma membrane and interact with receptors in the cytosol OR directly with the NUCLEUS (nuclear receptor) and is therefore able to carry our gene expression?
Lipophyllic homrones (non polar, hydrophobic)
What type of cell signal acts on "nearby" cells?
Paracrine
Some hormones can act on nearby cells or on the producing cell (even though most act on DISTANT targets). an example of this would be?
Retionic Acid Vitamin A (fat soluble)
What are 3 types of lipophillic hormones?
Steriod hormones (from cholestrol) thyroid hormones (T4 and T3) Retinoic Acid (Vitamin A)
What type of cell signal uses action potentials to transmit a signal mediated (carried out) by neurotransmitters?
Synaptic signal
4. In trimeric G proteins, GTP binds to a. the a (alpha) subunit. b. the B-beta subunit. c. the y-gamma subunit. d. the activated trimer.
The alpha subunit which causes the trimeric G protein to become active.
Thyroid hormones are reversibly bound by which protein? This allows it to move through circulation as an inactive hormone.
Thyroxine-binding globulin (TBG)
SIGNALLING AND BASIC REQUIREMENTS FOR SIGNAL TRANSDUCTION: The communication of messages from one cell to another cell that results in altered behavior of that TARGET CELL is referred to as what?
Transduction (also known as CELL SIGNALING)
DAG activates a. PKC. b. PKA. c. PLC. d. calmodulin.
a. PKC
13. Which of the following events occur(s) during the epinephrine-stimulated conversion of glycogen to glucose-1-phosphate? a. activation of PKA by cAMP b. inhibition of glycogen synthase c. activation of glycogen phosphorylase d. b and c e. all of the above
a. occurs when aenylyl cyclase converts ATP into cAMP which then activates PKA before activating glycogen phosphorylase kinase. b. glycogen synthase is inhibited by protein kinase a c. glycogen phosphorylase kinase activates glycogen phosphorylase (by donating a P group) answer: C.
2. Receptor tyrosine kinase: when you find one tyrosine kinase receptor you'll find another close by along the cell membrane When ligands bind to both receptors they then ______ together and ACT together forming a tyrosine ______. Receptor tyrosine kinase contain tyrosine AAs on the receptor portion INSIDE the CELL.
come, dimer (cross linked dimer)
Tradiotionally hormones have been known as ________ signalling molecules?
endocrine
15.5 G Protein-Coupled Receptors that Regulate Ion Channels use cGMP phosphodiesterase to catalyze the conversion of: a. cAMP to cGMP. b. cGMP to 5´-GMP. c. GTP to cGMP. d cGMP to GDP.
if its a cGMP phosphodiesterase Ik that its breaking down cGMP into something. so only options b and d are possible. the answer is b.
These hormones is derived from cholestrol?
steriod hormones
these hormones are sythesized and quickly released into the blood stream from the testease or ovaries for example, they are bound to carrier proteins in the blood, and can ONLY be uptaken by the target cell that they specify?
steroid hormones (testosterone, estrogen for example, travel through the blood bound. SHBG (sex hormone binding globulin = inactive when bound)
Overall, signalling molecules only act on target cells that posses ?
the appropriate receptor. Not just any cell can use whatever signal is out there. There are specific cell signals for each cell to use VIA its RECEPTOR.
which hormone is both made by AND secreted from the gland.
thyroid hormones
This lipophillic hormone's precursor is thyroglobulin ( a large glycoprotein).
thyroid hormones T4 and T3 (Active)