02.10 - Cell Signalling Flashcards
It refers to the conversion of one form of information to another, usually a biochemical response.
Signal transduction
What do you call the multiplication of the original signal?
Signal amplification
G proteins transmit a signal when:
a. Bound to GDP
b. Bound to GTP
c. Bound to ATP
d. Bound to ADP
b. Bound to GTP
Insulin, a hormone that is secreted by pancreatic B-cells and is delivered to muscle cells through the bloodstream, exhibits what mode of signalling?
a. Endocrine
b. Paracrine
c. Neuronal
d. Contact-dependent
a. Endocrine
When a signalling cell secretes a local mediator to transmit information to nearby target cells, the mode of signalling is called:
a. Endocrine
b. Paracrine
c. Neuronal
d. Contact-dependent
b. Paracrine
Acetylcholine is released in the synapse to send signals to target cells. This is an example of what type of signalling?
a. Endocrine
b. Paracrine
c. Neuronal
d. Contact-dependent
c. Neuronal
When a membrane-bound antibody binds to an antigenic residue, what type of signalling is exhibited?
a. Endocrine
b. Paracrine
c. Neuronal
d. Contact-dependent
d. Contact-dependent
True or False: A signalling molecule may induce different responses in different cell types.
True
Acetylcholine, a neurotransmitter, has several effects on different cell types. Which of the following cell-response is incorrectly paired ?
a. Heart muscle cell - increased rate of contraction
b. Salivary gland cell - secretion
c. Skeletal muscle cell - contraction
d. None of the above
a. Heart muscle cell - increased rate of contraction (Acetylcholine promotes DECREASED rate of contraction in heart muscle cells.)
What are the two types of extracellular signalling molecules?
Cell-surface receptors
Intracellular receptors
Which of the following statements is incorrect?
a. Hydrophilic signal molecules can diffuse through the membrane and initiate a response in the nucleus.
b. Cell-surface receptors are located on the plasma membrane.
c. Steroid hormones can bind to cell-surface receptors and induce cytoplasmic responses.
d. Intracellular receptors bind to signal molecules that diffuse from the extracellular environment into the nucleus.
a. Hydrophilic signal molecules can diffuse through the membrane and initiate a response in the nucleus. (Hydrophilic signals do not easily pass through the hydrophobic lipid bilayer.)
_________________ are intracellular molecules that change in concentration in response to environmental sigmas. They usually are involved in signal amplification.
Second messengers
Which of the following statements in incorrect?
a. No homology exists between the signal transduction pathways of mammals and insects.
b. cAMP is a secondary messenger.
c. Signaling pathways are redundant.
d. Signaling pathways converge and diverge.
a. No homology exists between the signal transduction pathways of mammals and insects.
Which of the following statements is incorrect?
a. Nitric oxide is a diffusible, hydrophobic signal that induces the relaxation of smooth muscle cells.
b. Acetylcholine serves as an extracellular signal for the conversion of arginine to nitric oxide.
c. Nitric oxide binds to a target protein inside the smooth muscle cell.
d. Conversion of arginine to nitric oxide occurs in smooth muscle cells.
d. Conversion of arginine to nitric oxide occurs in endothelial cells.
Which of the following statements about NO is incorrect?
a. NO is a reactive free-radical that acts either as a neurotransmitter or second messenger.
b. NO stimulates macrophages to kill tumor cells and bacteria.
c. In septic shock, increased NO may lower blood pressure to dangerous levels.
d. NO binds to the copper of the intracellular receptor guanylyl cyclase.
d. NO binds to the copper of the intracellular receptor guanylyl cyclase. (It binds to the IRON of guanylyl cyclase).
Which of the following leads to increased NO levels in an endothelial cell?
a. Release of acetylcholine by a cholinergic nerve
b. Increased inositol trisphosphate in the endothelial cell
c. Production of cavernous nerve
d. All of the above
d. All of the above
After NO binding to the iron of guanylyl cyclase:
a. cGMP is degraded to 5’ GMP
b. IP3 and DAG concentrations are increased
c. GTP is converted to cGMP
d. PDE5 is inhibited
c. GTP is converted to cGMP
Conversion of GTP to cGMP:
a. Leads to the activation of a protein kinase that induces the absorption of calcium ions by the ER
b. Produces sildenafil
c. Increases calcium concentration intracellularly
d. None of the above
a. Leads to the activation of a protein kinase that induces the absorption of calcium ions by the ER
Decreased calcium concentrations has what physiologic effect on smooth muscles?
a. Detachment of myosin head from actin
b. Smooth muscle relaxation
c. None of the above
d. A and B
d. A and B
Sildenafil:
a. Promotes the action of PDE 5
b. Prevents the conversion of cGMP to 5’ GMP
c. Maintains a high intracellular concentration of calcium
d. Induces smooth muscle contraction
b. Prevents the conversion of cGMP to 5’ GMP
PDE 5:
a. Catalyzes the formation of cGMP-specific protein kinase
b. Is produced from eNOS
c. Is inhibited by Viagra
d. Is the enzyme for the conversion of GTP to cGMP
c. Is inhibited by Viagra
The increase in the calcium concentration in the endoplasmic reticulum leads to:
a. Attachment of myosin to actin
b. Inhibition of PDE5
c. Smooth muscle relaxation
d. Binding of NO to the iron residue of guanylyl cyclase
c. Smooth muscle relaxation
Which of the following statements is correct?
a. Intracellular receptors can translocate to the nucleus and direct gene expression.
b. Membrane-bound receptor act immediately compared to intracellular receptors.
c. Regulation of gene expression by intracellular receptors may take hours or days.
d. All of the above are correct.
d. All of the above are correct.
True or False: Cytokine receptor superfamily are similar to receptor tyrosine kinases but have separate receptors and kinases.
True
In response to an extracellular signal, tyrosine kinase activates ____________, which hydrolyses PIP2 into two secondary messengers:
a. PLC-gamma
b. IP3
c. DAG
d. G-protein
a. PLC-gamma
Hydrolysis of phosphatidyl inositol bisphosphate generates:
a. DAG and G-protein
b. Adenylate cyclase and PLC
c. IP3 and adenylate cyclase
d. DAG and IP3
d. DAG and IP3
Which of the following increases cytoplasmic concentration of calcium?
a. IP3
b. Degradation of cGMP to 5’ GMP
c. cAMP-induced Ca uptake through calcium channels
d. All of the above
d. All of the above
Increased Ca concentration due to IP3 is followed by:
a. Activation of protein kinase C (PKC) bound to DAG
b. Degradation of DAG
c. Activation of adenylate cyclase
d. None of the above
a. Activation of protein kinase C (PKC) bound to DAG
What regulatory protein binds to calcium and serves as a calcium sensor in eukaryotic cell?
Calmodulin
Which of the following is a function of the calcium-calmodulin complex?
a. Activation of protein kinases
b. Stimulation of calcium-ATPase pump
c. Activation of adenylate cyclase
d. A and B
d. A and B
Arrange the following in order:
I - Adenylate cyclase catalyses cAMP formation
II - Alpha subunit moves to adenylate cyclase
III - Epinephrine binds to its specific receptor
IV - PKA activation by cAMP
V - Replacement of GDP bound to Gs by GTP
a. III-II-I-V-IV
b. III-V-IV-I-II
c. II-V-III-IV-I
d. III-V-II-I-IV
d. III-V-II-I-IV
Beta-1 adrenergic receptors are located in what organ?
Heart
Beta-2 receptors are found in which cells?
Epithelial cells
Beta-3 receptors are found in what tissue?
Adipose tissue
What drug favours binding to beta-1 adrenergic receptors?
Atenolol
How do G proteins reset themselves?
a. GTP Condensation
b. GTP Hydrolysis
c. GTP Dehydration
d. GTP Carboxylation
b. GTP Hydrolysis
What enzyme converts ATP into cyclic AMP?
Adenylyl cyclase
Which of the following is true?
a. IP3 is a hydrophilic sugar.
b. DAG is a hydrophobic lipid found in the membrane.
c. G proteins may activate adenylyl cyclase or phospholipase C.
d. All of the above
d. All of the above
What enzyme degrades cAMP?
cAMP phosphodiesterase
Cyclic AMP phosphorylates cAMP-dependent protein kinase (PKA). What is the action of PKA?
a. Phosphorylation of other enzymes
b. Phosphorylation of transcriptional activators (e.g. binding of CREB to CRE)
c. Phosphorylation of potassium channels to close them
d. All of the above.
d. All of the above.
What enzyme catalyses the conversion of glucose to glycogen?
Glycogen synthase
What enzyme catalyses the conversion of glycogen to glucose?
Glycogen phosphorylase
What happens after phosphorylation of glycogen synthase?
a. Inactivation of glycogen synthase
b. Inhibition of glycogen synthesis
c. Breakdown of glycogen to glucose
d. A and B
d. A and B
What happens when glycogen phosphorylase is phosphorylated?
a. Inactivation of glycogen phosphorylase
b. Breakdown of glycogen to glucose
c. Activation of glycogen phosphorylase
d. B and C
d. B and C
PKA phosphorylates potassium channels to close them. What is the result of the closure of K channels?
Increased excitability of the target cell
True or False: G-protein coupled receptor can also involve phospholipase C and thus IP3/DAG signalling.
True
What is wrong with G-protein activity in cholera?
G-protein is always active
Pertussis or whooping cough results from __________ of G protein.
Inactivation
