BIO 2B03 Final Exam Review
questions with answers
Endocrine signaling - correct answer ✔✔ one type of secretory signaling, signals enter the
circulatory system and circulate systemically. This signal is usually a hormone, and the target
tissue may be far from the place where the signal originated
Paracrine signaling - correct answer ✔✔ one type of secretory signaling, signals are released
into the extracellular space and interact with neighboring cells. Signals may be growth factors or
neurotransmitters, for example. This type of signaling only targets proximal to the point of
signal origin
Integral membrane proteins signaling - correct answer ✔✔ one type of cell-cell contact
signaling, this involves the use of receptors in the cell membrane that bind to signalling
molecules, and targets neighboring cells
Plasmodesmata - correct answer ✔✔ one type of cell-cell contact signaling, these are present
only in plants, and connect the cytoplasm of neighboring cells, allowing cytosolic signals to pass
from cell to cell
Gap junctions - correct answer ✔✔ one type of cell-cell contact signaling, these are present
only in animal cells, and connect the cytoplasm of neighboring cells, allowing cytosolic signals to
pass from cell to cell
Autocrine signaling - correct answer ✔✔ one type of signaling where the signal's origin and
target are the same cell. One example of a signal that falls under this category are growth
factors that regulate cell division
JAK-STAT pathway - correct answer ✔✔ signal: erythropoietin (Epo)
,receptor: EpoR
intracellular transduction: JAK kinases and STAT transcription factors
response: erythroid progenitor cells proliferate, new RBCs are made
EpoR - correct answer ✔✔ JAK-STAT pathway; an integral membrane protein receptor with a
cytosolic domain containing JAK kinases. These receptors dimerize upon interacting with the
signal protein (Epo) and they autophosphorylate, activating the kinases
JAK kinase - correct answer ✔✔ JAK-STAT pathway; this refers to the cytosolic domain of the
EpoR receptor. This protein domain acts as a tyrosine kinase domain, that will become active
upon receptor dimerization and autophosphorylation
STAT transcription factors - correct answer ✔✔ JAK-STAT pathway; these are transcription
factors that, upon interacting with the phosphorylated Tyr residues on the EpoR receptor,
become phosphorylated and homodimerize. Now that they're active, they can enter the
nucleus, bind to DNA, and initiate transcription of target genes
SH2 domain - correct answer ✔✔ JAK-STAT pathway; this domain is found on the STAT
transcription factor. It binds to phosphorylated Tyr residues, meaning that protein-protein
binding can be reversed
STAT5 - correct answer ✔✔ JAK-STAT pathway; this member of the STAT transcription factor
family increases the transcription of apoptosis-preventing genes, in order to allow
differentiation of erythroid progenitor cells
, SHP1 phosphatase - correct answer ✔✔ JAK-STAT pathway; this phosphatase acts to short-term
stop the signaling pathway by dephosphorylating the SH2 domain on STAT transcription factors,
causing them to become inactive monomers
SOCS - correct answer ✔✔ JAK-STAT pathway; this protein stops the signaling pathway long-
term by blocking binding sites on the EpoR functional domain and ubiquitinylating JAK kinases--
marking them for degradation
RTK/Ras pathway - correct answer ✔✔ signal: growth factors (NGF, PDGF, EGF, insulin)
receptor: Receptor tyrosine kinase
intracellular transduction: adaptors (GRB2), Ras proteins (GTPases), Ras effectors (GEF and
GAP), phosphorylation cascade, MAP kinase, transcription factors
response: cell differentiation, division, survival/apoptosis, metabolism
RTK - correct answer ✔✔ RTK/Ras pathway; the receptor that starts it all. this binds with an
incoming growth factor ligand (eg, EGF) which induces receptor dimerization and
autophosphorylation
Adaptor proteins - correct answer ✔✔ these proteins carry multiple protein-interacring
domains, and are often present linking together different steps in signal transduction
GRB2 - correct answer ✔✔ RTK/Ras pathway; this is an adaptor protein that contains an SH2
domain that interacts with p-Tyr residues on RTK, and two SH3 domains that recognize Pro-rich
sequences and bind to SOS
questions with answers
Endocrine signaling - correct answer ✔✔ one type of secretory signaling, signals enter the
circulatory system and circulate systemically. This signal is usually a hormone, and the target
tissue may be far from the place where the signal originated
Paracrine signaling - correct answer ✔✔ one type of secretory signaling, signals are released
into the extracellular space and interact with neighboring cells. Signals may be growth factors or
neurotransmitters, for example. This type of signaling only targets proximal to the point of
signal origin
Integral membrane proteins signaling - correct answer ✔✔ one type of cell-cell contact
signaling, this involves the use of receptors in the cell membrane that bind to signalling
molecules, and targets neighboring cells
Plasmodesmata - correct answer ✔✔ one type of cell-cell contact signaling, these are present
only in plants, and connect the cytoplasm of neighboring cells, allowing cytosolic signals to pass
from cell to cell
Gap junctions - correct answer ✔✔ one type of cell-cell contact signaling, these are present
only in animal cells, and connect the cytoplasm of neighboring cells, allowing cytosolic signals to
pass from cell to cell
Autocrine signaling - correct answer ✔✔ one type of signaling where the signal's origin and
target are the same cell. One example of a signal that falls under this category are growth
factors that regulate cell division
JAK-STAT pathway - correct answer ✔✔ signal: erythropoietin (Epo)
,receptor: EpoR
intracellular transduction: JAK kinases and STAT transcription factors
response: erythroid progenitor cells proliferate, new RBCs are made
EpoR - correct answer ✔✔ JAK-STAT pathway; an integral membrane protein receptor with a
cytosolic domain containing JAK kinases. These receptors dimerize upon interacting with the
signal protein (Epo) and they autophosphorylate, activating the kinases
JAK kinase - correct answer ✔✔ JAK-STAT pathway; this refers to the cytosolic domain of the
EpoR receptor. This protein domain acts as a tyrosine kinase domain, that will become active
upon receptor dimerization and autophosphorylation
STAT transcription factors - correct answer ✔✔ JAK-STAT pathway; these are transcription
factors that, upon interacting with the phosphorylated Tyr residues on the EpoR receptor,
become phosphorylated and homodimerize. Now that they're active, they can enter the
nucleus, bind to DNA, and initiate transcription of target genes
SH2 domain - correct answer ✔✔ JAK-STAT pathway; this domain is found on the STAT
transcription factor. It binds to phosphorylated Tyr residues, meaning that protein-protein
binding can be reversed
STAT5 - correct answer ✔✔ JAK-STAT pathway; this member of the STAT transcription factor
family increases the transcription of apoptosis-preventing genes, in order to allow
differentiation of erythroid progenitor cells
, SHP1 phosphatase - correct answer ✔✔ JAK-STAT pathway; this phosphatase acts to short-term
stop the signaling pathway by dephosphorylating the SH2 domain on STAT transcription factors,
causing them to become inactive monomers
SOCS - correct answer ✔✔ JAK-STAT pathway; this protein stops the signaling pathway long-
term by blocking binding sites on the EpoR functional domain and ubiquitinylating JAK kinases--
marking them for degradation
RTK/Ras pathway - correct answer ✔✔ signal: growth factors (NGF, PDGF, EGF, insulin)
receptor: Receptor tyrosine kinase
intracellular transduction: adaptors (GRB2), Ras proteins (GTPases), Ras effectors (GEF and
GAP), phosphorylation cascade, MAP kinase, transcription factors
response: cell differentiation, division, survival/apoptosis, metabolism
RTK - correct answer ✔✔ RTK/Ras pathway; the receptor that starts it all. this binds with an
incoming growth factor ligand (eg, EGF) which induces receptor dimerization and
autophosphorylation
Adaptor proteins - correct answer ✔✔ these proteins carry multiple protein-interacring
domains, and are often present linking together different steps in signal transduction
GRB2 - correct answer ✔✔ RTK/Ras pathway; this is an adaptor protein that contains an SH2
domain that interacts with p-Tyr residues on RTK, and two SH3 domains that recognize Pro-rich
sequences and bind to SOS
