CPPS 325 FINAL EXAM QUESTIONS WITH
CORRECT ANSWERS 2025
What are the 5 well-known enzyme-linked cell surface receptors? - CORRECT ANSWER -
1. Receptor Guanylyl Cyclase: produces cGMP
2. RTK: phosphorylate tyrosine residues leading to association of signalling molecules and cascade
3. TK Associated Receptors: associate with proteins having TK activity
4. Receptor Tyrosine Phosphates: Removes phosphate on tyrosine residues
5. Receptor Serine/Threonine Kinases: phosphorylate specific Serine/Threonine residues on IC signallin
g molecules
How are RTK and TK Associated Receptors different? - CORRECT ANSWER -
RTK phosphorylate tyrosine while associated receptors bind/find proteins with TK activity to initiate th
e cascade of signalling.
What is the reciprocal of RTK? - CORRECT ANSWER -
Receptor Tyrosine Phosphatases. They take the phosphate off the tyrosine residues to inactivate signalli
ng cascades.
Ex. Transforming GF Beta superfamily of receptors, cell type dependent.
What is the major mechanism for receptor signal transduction? - CORRECT ANSWER -
Tyrosine kinase phosphorylation
RTK vs. Serine/Threonine Phosphorylation ? - CORRECT ANSWERV-
Tyrosine phosphorylation is rare (1%) relative to serine/threonine residue phosphorylation. Tyrosine ph
osphorylation is the major mechanism of receptor signal transduction.
What is the net effect of activated TKs? - CORRECT ANSWER -
Tyrosine phosphorylation on target proteins.
What do TK pathways mediate? - CORRECT ANSWERV-
Cell growth (growth factors), differentiation, host defense, metabolic regulation, cell survival pathways
(survival factors).
What are amplifiers of the TK pathways? - CORRECT ANSWERV-PI3-K -> PIP3
PLC -> DAG and InsP3&Ca2+
What are RTK mediated actions in the cell? - CORRECT ANSWER -
regulation of cell proliferation, differentiation, and cell motility, promotion of cell survival and modulat
ion of cellular metabolism.
TKs exist in either the cytosol or as transmembrane receptors, what are the differences in the two types
? - CORRECT ANSWER -Cytosol receptors have an src N-
terminal region. Cytosol has no membrane spanning domain.
TM receptor has a single membrane spanning hydrophobic TM domain. Ex) Epidermal GF RTK.
What is src? - CORRECT ANSWER -Src is a non-
,receptor TK, so it does not span a membrane. It is a tyrosine kinase. And although it is cytoplasmic T
K it can still bind to activated RTKs.
What is contact inhibition confluency? - CORRECT ANSWER -
Stops Src domains signalling and therefore cells stop dividing.
If there is an issue then cancer can result and mutation causes an inhibition of the stop signal so the ce
lls keep growing and dividing.
What are SH domains? - CORRECT ANSWER -
Src homology domains. Src and other proteins that have src-
homology domains can bing to activated RTKs.
What are the different SH domains in proteins? - CORRECT ANSWER -
There are SH1, SH2 and SH3 domains.
What isSH1 domain characterized by? - CORRECT ANSWER -
Catalytic domain of a protein, for example the receptor. and it has the kinase activity. It is responsible
for phosphorylating tyrosine residues.
What is SH2 domain characterized by? - CORRECT ANSWERV-
Binds peptides with consensus (positional information on C-
terminal side of the phosphorylated tyrosine).
Very specific.
Mediates protein-
protein interactions in cellular signalling cascades. Very common in proteins outside the src family.
What do SH2 and SH3 domains have as a common funciton? - CORRECT ANSWERV-
They mediate protein-protein interactions in cellular signalling cascades.
Very common in proteins outside the src family.
What is SH3 domain characterized by? - CORRECT ANSWERV-Interacts with proline-
rich peptide targets (minimal consensus). Mediate protien-
protein interatctions in the cellular signalling cascade. Very common in proteins outside the src family.
What are PTB domains? - CORRECT ANSWERV-(Phosphotyrosine binding domain)
Bind to phosphorylated tyrosine. Functional equivalent of the SH2 domain, except for the positional inf
ormational. Is not the C-terminus like SH2, but the N-terminus side of the phosphorylated tyrosine.
shc is a PTB protein.
What is the normal action that stops signalling for cell division in the src pathway? -
CORRECT ANSWER -Contact Inhibition Confluency
How do PTB and SH2 domains differ? - CORRECT ANSWERV-
SH2 domains binds consensus on the C-terminus.
PTB domains binds the N-terminus.
They both mediate cellular signalling.
What is shc? - CORRECT ANSWER -PTB protein that docks at the N-
terminus consensus docking site.
, What activates a RTK? - CORRECT ANSWER -Ligand/agonist binding
Upon ligand binding the two activation pathways are? - CORRECT ANSWER -
1. Conformational change
2. Dimerization
What happens with conformational change activation? - CORRECT ANSWER -
A conformational change that is sufficient enough to activate SH1/catalytic domain results in phosphor
ylation.
What is the only example of conformational change activation? - CORRECT ANSWER -
Insulin receptor kinase.
All other RTKs are activated through forms of dimerization.
What are the two forms of dimerization? - CORRECT ANSWERV-
i) Receptors exist as unactivated dimers until ligand binds (Twist theory)
ii) exist as monomers that are brought together and activated by ligand binding.
What is the most common method of dimerization activation? - CORRECT ANSWERV-
Receptors existing as monomers.
What is the Twist Theory? - CORRECT ANSWER -
RTKs exist as formed dimers and when a ligand binds the dimer undergoes a twist/shift in shape so th
e catalytic domains can become fully active and therefore allow for autophosphorylation in key tyrosin
e residues outside the catalytic domain.
What is the monomer dimerization activation pathway? - CORRECT ANSWERV-
The monomers need to dimerize to fully activate the TK/SH1 domains.
Ligand must bind external domains of two monomer RTKs so they dimerize. This results in increased
enzymatic activity of the IC catalytic SH1/TK domains by phosphorylating key tyrosine residues outsid
e the catalytic domain. Transphosphorylation of tyrosines occurs so the kinase activation can occur, an
d transphosphorylation of regions that create the docking site. The phosphorylated tyrosine residues ser
ve as docking sites for cytoplasmic signalling molecules.
What does RTK activation require? - CORRECT ANSWER -Dimerization and transphosphorylation!!
Where are tyrosines phosphorylated - CORRECT ANSWER -
They are first phosphorylated within the kinase/catalytic domains to increase the activity of enzyme an
d this triggers phosphorylation outside the catalytic/kinase domain that produces a docking site.
What does phosphorylation of tyrosines within the kinase/catalytic domain do? -
CORRECT ANSWER -Increases the kinase activity of the enzyme.
What does phosphorylation of tyrosines outside the kinase/catalytic domain do? -
CORRECT ANSWER -It creates high-affinity binding sites for a number of IC signalling properties.
What are some IC signalling proteins that bind to the docking sites created by phosphorylation outside
the kinase/catalytic domain? - CORRECT ANSWER --
PLC (amplifiers) which leads to release of Ca2+
-SRC TK (non-receptor TK)
-Adaptor proteins like Grb-2. (activation of Grb-2 leads to recruitment of SOS and activation of Ras)
CORRECT ANSWERS 2025
What are the 5 well-known enzyme-linked cell surface receptors? - CORRECT ANSWER -
1. Receptor Guanylyl Cyclase: produces cGMP
2. RTK: phosphorylate tyrosine residues leading to association of signalling molecules and cascade
3. TK Associated Receptors: associate with proteins having TK activity
4. Receptor Tyrosine Phosphates: Removes phosphate on tyrosine residues
5. Receptor Serine/Threonine Kinases: phosphorylate specific Serine/Threonine residues on IC signallin
g molecules
How are RTK and TK Associated Receptors different? - CORRECT ANSWER -
RTK phosphorylate tyrosine while associated receptors bind/find proteins with TK activity to initiate th
e cascade of signalling.
What is the reciprocal of RTK? - CORRECT ANSWER -
Receptor Tyrosine Phosphatases. They take the phosphate off the tyrosine residues to inactivate signalli
ng cascades.
Ex. Transforming GF Beta superfamily of receptors, cell type dependent.
What is the major mechanism for receptor signal transduction? - CORRECT ANSWER -
Tyrosine kinase phosphorylation
RTK vs. Serine/Threonine Phosphorylation ? - CORRECT ANSWERV-
Tyrosine phosphorylation is rare (1%) relative to serine/threonine residue phosphorylation. Tyrosine ph
osphorylation is the major mechanism of receptor signal transduction.
What is the net effect of activated TKs? - CORRECT ANSWER -
Tyrosine phosphorylation on target proteins.
What do TK pathways mediate? - CORRECT ANSWERV-
Cell growth (growth factors), differentiation, host defense, metabolic regulation, cell survival pathways
(survival factors).
What are amplifiers of the TK pathways? - CORRECT ANSWERV-PI3-K -> PIP3
PLC -> DAG and InsP3&Ca2+
What are RTK mediated actions in the cell? - CORRECT ANSWER -
regulation of cell proliferation, differentiation, and cell motility, promotion of cell survival and modulat
ion of cellular metabolism.
TKs exist in either the cytosol or as transmembrane receptors, what are the differences in the two types
? - CORRECT ANSWER -Cytosol receptors have an src N-
terminal region. Cytosol has no membrane spanning domain.
TM receptor has a single membrane spanning hydrophobic TM domain. Ex) Epidermal GF RTK.
What is src? - CORRECT ANSWER -Src is a non-
,receptor TK, so it does not span a membrane. It is a tyrosine kinase. And although it is cytoplasmic T
K it can still bind to activated RTKs.
What is contact inhibition confluency? - CORRECT ANSWER -
Stops Src domains signalling and therefore cells stop dividing.
If there is an issue then cancer can result and mutation causes an inhibition of the stop signal so the ce
lls keep growing and dividing.
What are SH domains? - CORRECT ANSWER -
Src homology domains. Src and other proteins that have src-
homology domains can bing to activated RTKs.
What are the different SH domains in proteins? - CORRECT ANSWER -
There are SH1, SH2 and SH3 domains.
What isSH1 domain characterized by? - CORRECT ANSWER -
Catalytic domain of a protein, for example the receptor. and it has the kinase activity. It is responsible
for phosphorylating tyrosine residues.
What is SH2 domain characterized by? - CORRECT ANSWERV-
Binds peptides with consensus (positional information on C-
terminal side of the phosphorylated tyrosine).
Very specific.
Mediates protein-
protein interactions in cellular signalling cascades. Very common in proteins outside the src family.
What do SH2 and SH3 domains have as a common funciton? - CORRECT ANSWERV-
They mediate protein-protein interactions in cellular signalling cascades.
Very common in proteins outside the src family.
What is SH3 domain characterized by? - CORRECT ANSWERV-Interacts with proline-
rich peptide targets (minimal consensus). Mediate protien-
protein interatctions in the cellular signalling cascade. Very common in proteins outside the src family.
What are PTB domains? - CORRECT ANSWERV-(Phosphotyrosine binding domain)
Bind to phosphorylated tyrosine. Functional equivalent of the SH2 domain, except for the positional inf
ormational. Is not the C-terminus like SH2, but the N-terminus side of the phosphorylated tyrosine.
shc is a PTB protein.
What is the normal action that stops signalling for cell division in the src pathway? -
CORRECT ANSWER -Contact Inhibition Confluency
How do PTB and SH2 domains differ? - CORRECT ANSWERV-
SH2 domains binds consensus on the C-terminus.
PTB domains binds the N-terminus.
They both mediate cellular signalling.
What is shc? - CORRECT ANSWER -PTB protein that docks at the N-
terminus consensus docking site.
, What activates a RTK? - CORRECT ANSWER -Ligand/agonist binding
Upon ligand binding the two activation pathways are? - CORRECT ANSWER -
1. Conformational change
2. Dimerization
What happens with conformational change activation? - CORRECT ANSWER -
A conformational change that is sufficient enough to activate SH1/catalytic domain results in phosphor
ylation.
What is the only example of conformational change activation? - CORRECT ANSWER -
Insulin receptor kinase.
All other RTKs are activated through forms of dimerization.
What are the two forms of dimerization? - CORRECT ANSWERV-
i) Receptors exist as unactivated dimers until ligand binds (Twist theory)
ii) exist as monomers that are brought together and activated by ligand binding.
What is the most common method of dimerization activation? - CORRECT ANSWERV-
Receptors existing as monomers.
What is the Twist Theory? - CORRECT ANSWER -
RTKs exist as formed dimers and when a ligand binds the dimer undergoes a twist/shift in shape so th
e catalytic domains can become fully active and therefore allow for autophosphorylation in key tyrosin
e residues outside the catalytic domain.
What is the monomer dimerization activation pathway? - CORRECT ANSWERV-
The monomers need to dimerize to fully activate the TK/SH1 domains.
Ligand must bind external domains of two monomer RTKs so they dimerize. This results in increased
enzymatic activity of the IC catalytic SH1/TK domains by phosphorylating key tyrosine residues outsid
e the catalytic domain. Transphosphorylation of tyrosines occurs so the kinase activation can occur, an
d transphosphorylation of regions that create the docking site. The phosphorylated tyrosine residues ser
ve as docking sites for cytoplasmic signalling molecules.
What does RTK activation require? - CORRECT ANSWER -Dimerization and transphosphorylation!!
Where are tyrosines phosphorylated - CORRECT ANSWER -
They are first phosphorylated within the kinase/catalytic domains to increase the activity of enzyme an
d this triggers phosphorylation outside the catalytic/kinase domain that produces a docking site.
What does phosphorylation of tyrosines within the kinase/catalytic domain do? -
CORRECT ANSWER -Increases the kinase activity of the enzyme.
What does phosphorylation of tyrosines outside the kinase/catalytic domain do? -
CORRECT ANSWER -It creates high-affinity binding sites for a number of IC signalling properties.
What are some IC signalling proteins that bind to the docking sites created by phosphorylation outside
the kinase/catalytic domain? - CORRECT ANSWER --
PLC (amplifiers) which leads to release of Ca2+
-SRC TK (non-receptor TK)
-Adaptor proteins like Grb-2. (activation of Grb-2 leads to recruitment of SOS and activation of Ras)
