Intracellular signalling - Exam Questions Flashcards
When does intercellular signalling occur?
When a cell surface ligand directly binds to its receptor on the target cell.
Cytokines are an example of
a. inter-cellular signalling
b. paracrine signalling
c. endocrine signalling
d. exocrine signalling
e. neuronal signalling
b. Cytokines are an exmaple of paracrine signalling
Paracrine signalling = signal acts on cells very close to the cell that produced it
Acetyl choline, glutamate, dopamine, noradrenaline and GABA are all a. hormones b. amino acids c. inflammatory mediators d. neurotransmitters e. catecholamines
d. Acetyl choline, glutamate, dopamine, noradrenaline and GABA are all neurotransmitters
Match the signal molecule to its chemical type.
a. Insulin
b. Oestradiol
c. Adrenaline
d. Nitric oxide
e. Testosterone
i. Amino acid derivative
ii. Steroid
iii. Gas
iv. Glycosaminoglycan
v. Protein
Insulin=Protein Oestrdiol=Steroid Adrenaline=Amino acid derivative Nitric oxide=Gas Testosterone=Steroid
An example of a cell surface receptor is the receptor for
a. cortisol
b. adenylate cyclase
c. thyroxine
d. glucagon
e. cAMP
d. The receptor for glucagon is a cell surface receptor.
Tyrosine kinase receptors
a. are intracellular receptors
b. are activated by autophosphorylation
c. are G-protein-linked
d. are ion channels
e. bind steroid hormones
b. Tyrosine kinase receptors are activated by autophosphorylation
A signal molecule
a. never enters a cell
b. is a second messenger
c. activates a protein kinase
d. is a primary messenger
e. binds to a second messenger
d. A signal molecule is a primary messenger
The tissue response to a signal molecule
a. is always exactly the same in all tissues
b. varies slightly per tissue, but is always of a similar nature
c. is always the same where the receptor type is the same
d. may be completely different in different tissues
e. varies depending on differences in the signal molecule between
tissues
d. The tissue response to a signal molecule may be completely different in different tissues
Adaptor proteins
a. include Ras
b. associate with the signal molecule
c. are second messengers
d. generate the second messenger
e. associate with the ligand receptor
e. Adaptor proteins associate with the ligand receptor
Second messengers
a. are usually protein kinases
b. activate cAMP
c. are released into the cytosol in response to an extracellular signal
d. are formed in response to activation of a protein kinase
e. include G-proteins
c. second messengers are released into the cytosol in response to an extracellular signal
What does cAMP activate?
Protein kinase A
Protein Kinase A causes phosphorylation of…?
Serine residues
A phosphorylation cascade is when
a. a protein is sequentially phosphorylated and dephosphorylated
b. proteins autophosphorylate in response to a cascade of ligands
binding to them
c. kinases sequentially phosphorylate other kinases
d. proteins are successively phosphorylated by a kinase
e. all proteins in a cell are phosphorylated in response to a signal
A phosphorylation cascade is when kinases sequentially phosphorylate other kinases
Give an advantage of a phosphorylation cascade.
Signal amplification
The action of inositol trisphosphate as a second messenger is to
a. activate diacylglycerol
b. open calcium channels on the endoplasmic reticulum
c. stimulate protein kinase C to translocate to the plasma membrane
d. activate phospholipase C
e. activate protein kinase C
b. The action of inositol triphosphate as a secondary messenger is to open calcium channels on the endoplasmic reticulum.
What is the action of calcium as a secondary messenger?
Activates calcium-dependent protein kinase
What is protein kinase C activated by?
DAG (diacylglycerol)
cGMP is activated as a second messenger by a signal molecule binding to a. a G-protein linked receptor b. protein kinase C c. cGMP-dependent protein kinase d. GTP e. guanylate cyclase
e. cGMP is activated as a second messenger by a signal molecule binding to guanylate cyclase
Nitric oxide is produced by nitric oxide synthase from
a. glycine
b. glutamate
c. glutamine
d. arginine
e. asparagine
d. nitric oxide is produce by nitric oxide synthase from arginine
What does nitric oxide activate as a secondary messenger?
Guanylate cyclase
Signal termination occurs
a. whenever the signal molecule unbinds from the receptor
b. by means of passive dephosphorylation, in most cases
c. whenever the ultimate biological effect of the signal pathway is
produced
d. only through degradation of the receptor-ligand complex
e. by removal of the second messenger, in some cases
e. Signal termination occurs by removal of the second messenger
Match the receptor to its type.
a. Steroid hormone
b. Nicotinic
c. β-adrenergic
d. Insulin
e. Cannabinoid
f. Muscarinic
i. G-protein coupled
ii. intracellular
iii. ion channel
iv. tyrosine kinase
Steroid hormone=intracellular Nicotinic=Ion channel β-adrenergic=G-protein coupled Insulin=Tyrosine kinase Cannabinoid=G-protein coupled Muscarinic=G-protein coupled
What are Tyrosine Kinase receptors?
Catalytic
Match the G-protein-linked receptor to its intracellular signalling pathway a. vasopressin b. thrombin c. β-adrenergic d. muscarinic e. glucagon i. Gs – stimulates production of cAMP ii. Gi – inhibits production of cAMP iii. activates phospholipase C
Vasopressin=activates phospholipase C
Thrombin=activates phospholipase C
β-adrenergic=Gs - stimulates production of cAMP
Muscarinic=activates phospholipase C
Glucagon=Gi - inhibits production of cAMP
How many times do G-protein-linked receptors cross the cell membrane?
7 times
G-proteins are all
a. heterotrimeric
b. linked to G-protein-coupled receptors
c. monomeric
d. active when bound to GTP
e. 7-pass membrane proteins
d. G-proteins are all active when bound to GTP
When activated, heterotrimeric G proteins
a. dissociate their α subunit from their βγ subunits
b. associate with a tyrosine kinase receptor
c. dissociate into three individual subunits, α, β, and γ
d. activate protein kinase A
e. exchange GTP for GDP
a. When activated, heterotrimeric G-proteins dissociate their alpha subunits from their beta-gamma subunits
The tyrosine kinase domain of tyrosine kinase receptors is located
a. extracellularly
b. on a G-protein
c. intracellularly
d. in the transmembrane part of the receptor
e. one domain extracellularly, one domain intracellularly
c. The tyrosine kinase domain of tyrosine kinase receptors are located intracellularly
Which part of the tyrosine kinase receptor does insulin bind to?
The alpha-subunit
Ligand binding to a tyrosine kinase receptor induces
a. activation of guanylate cyclase
b. autophosphorylation of the tyrosine kinase domain
c. binding of Akt to the receptor
d. activation of a G-protein
e. substrate binding to the tyrosine kinase domain
b. Ligan binding to a tyrosine kinase receptor induces autophosphorylation of the tyrosine kinase domain.
What is the metabolic effects of insulin mediated by?
Akt
What inactivates cAMP?
Phosphodiesterase
Insulin’s moitogenic pathways are mediated by
a. Akt
b. Protein kinase A
c. Protein kinase C
d. cAMP
e. Ras
e. Insulin’s moitogenic pathways are mediated by Ras
The sequence of the pathway involving Ras is
a. Raf-Ras-MEK kinase-MAPK-transcription factor
b. Ras-Raf-MAPK-MEK kinase-transcription factor
c. transcription factor-Raf-MEK kinase-MAPK-Ras
d. Ras-Raf-MEK kinase-MAPK-transcription factor
e. Raf-Ras-MAPK-MEK kinase-transcription factor
d. Ras - Raf -MEK kinase - MAPK - transcription factor
How many subunits do acetylcholine receptors have?
5 subunits
