CHE 4342 Cell Signaling Exam Questions and Answers Already Passed Latest Update 2025-
2026
Direct Signaling - Answers cell to cell, contact dependent, occurs through proteins in the plasma
membrane
endocrine signaling - Answers occurs through hormones on distant target cells, long range
travels through the blood stream
paracrine signaling - Answers occurs through neurotransmitters and cytokines on nearby target
cells, short range
synaptic signaling - Answers a subset of paracrine signaling, occurs on neurotransmitters and
post synaptic cells in response to an electric stimuli
Autocrine signaling - Answers occurs through growth factors and the cell that releases the
signal is also the target
True or false: an effector has the same effect on all tissues - Answers false: acetyl choline
results in a contraction in a skeletal muscle cell but a relaxation in heart muscles.
How many subunits do small g proteins have - Answers one, mono numeric
How many subunits do big g proteins have - Answers 3, tri numeric
GCPRs - Answers G-protein coupled receptors
What is another name for GCPRs - Answers serpentine receptors
What is the structural motif of GCPRs - Answers 7 membrane spanning alpha helices (7TM)
True or false: the big g protein can bind the receptor only in the active state - Answers true
Where is the g protein located - Answers in the cytosol, not attached to the receptor
Where is the receptor located - Answers It spans the membrane
What happens when a ligand binds the receptor - Answers Conformational changes occur
throughout the membrane to the cytosolic side of the cell which results in an increase in affinity
between the GCPR and big g protein
What occurs with the G protein is activated - Answers the gdp is transformed to gtp and the
alpha subunit separates from the gamma and beta subunits (heterodimer), both parts of the
protein are active and participate in the signaling pathway
What keeps the subunits of the g protein near the membrane - Answers lipid proteins
What is the first off switch of the AC signaling cascade - Answers It is when GTPase adds what
, across the alpha subunit which turns GTP into GDP, stopping the signaling cascade.
What is GTPase activity enhanced by - Answers auxillary proteins
True or false: you only need one off switch to stop a signaling cascade - Answers false
Isoform - Answers homologous g proteins that impact different signaling cascades or target
proteins.
What is the second messenger of the adenylyl cyclase cascade - Answers cAMP (made from
ATP)
What enzyme turns ATP into cAMP? - Answers PPI (pyrophospate)
Why do the subunits of the big g protein disassociate when it is activated? - Answers the extra
phosphate on the GTP results in a net negative charge on the molecule which causes
dissociation
What is the 2nd off switch in the AC signaling pathway and how does it work? - Answers cAMP
phosphodiesterase, it adds 4 water molecules to 4cAMP which results in 4AMP.
What do the R and C components mean in PKA? - Answers PKA: Protein kinase A
R: regulator
C: catalytic subunits
Why are catalytic subunits important? - Answers when the catalytic subunits are off, the protein
is off, allosteric activation
What is the third off switch of the AC pathway and what does it do? - Answers Phosphoprotein
phosphatase (PP), it catalyzes the removal of a phosphate by hydrolysis of phosphates that
were attached to proteins via PKA, adds water across the phosphoester linkage
What is a second messenger and give examples? - Answers A molecule inside cells that acts to
transmit signals from a receptor to a target, (cAMP, cGAMP, DAG, IP3, PIP3, Ca2+, NO nitric
oxide)
What is the fourth off point of the AC pathway? - Answers External inhibitory signal, reverts GTP
to GDP
What is the fifth off signal of the AC pathway? - Answers receptor desentization
Where are first messengers located? - Answers Outside of the cell
How many cAMP bind to each regulator in the AC pathway? - Answers 2
How many PPi are required to make 4 cAMP - Answers 4
2026
Direct Signaling - Answers cell to cell, contact dependent, occurs through proteins in the plasma
membrane
endocrine signaling - Answers occurs through hormones on distant target cells, long range
travels through the blood stream
paracrine signaling - Answers occurs through neurotransmitters and cytokines on nearby target
cells, short range
synaptic signaling - Answers a subset of paracrine signaling, occurs on neurotransmitters and
post synaptic cells in response to an electric stimuli
Autocrine signaling - Answers occurs through growth factors and the cell that releases the
signal is also the target
True or false: an effector has the same effect on all tissues - Answers false: acetyl choline
results in a contraction in a skeletal muscle cell but a relaxation in heart muscles.
How many subunits do small g proteins have - Answers one, mono numeric
How many subunits do big g proteins have - Answers 3, tri numeric
GCPRs - Answers G-protein coupled receptors
What is another name for GCPRs - Answers serpentine receptors
What is the structural motif of GCPRs - Answers 7 membrane spanning alpha helices (7TM)
True or false: the big g protein can bind the receptor only in the active state - Answers true
Where is the g protein located - Answers in the cytosol, not attached to the receptor
Where is the receptor located - Answers It spans the membrane
What happens when a ligand binds the receptor - Answers Conformational changes occur
throughout the membrane to the cytosolic side of the cell which results in an increase in affinity
between the GCPR and big g protein
What occurs with the G protein is activated - Answers the gdp is transformed to gtp and the
alpha subunit separates from the gamma and beta subunits (heterodimer), both parts of the
protein are active and participate in the signaling pathway
What keeps the subunits of the g protein near the membrane - Answers lipid proteins
What is the first off switch of the AC signaling cascade - Answers It is when GTPase adds what
, across the alpha subunit which turns GTP into GDP, stopping the signaling cascade.
What is GTPase activity enhanced by - Answers auxillary proteins
True or false: you only need one off switch to stop a signaling cascade - Answers false
Isoform - Answers homologous g proteins that impact different signaling cascades or target
proteins.
What is the second messenger of the adenylyl cyclase cascade - Answers cAMP (made from
ATP)
What enzyme turns ATP into cAMP? - Answers PPI (pyrophospate)
Why do the subunits of the big g protein disassociate when it is activated? - Answers the extra
phosphate on the GTP results in a net negative charge on the molecule which causes
dissociation
What is the 2nd off switch in the AC signaling pathway and how does it work? - Answers cAMP
phosphodiesterase, it adds 4 water molecules to 4cAMP which results in 4AMP.
What do the R and C components mean in PKA? - Answers PKA: Protein kinase A
R: regulator
C: catalytic subunits
Why are catalytic subunits important? - Answers when the catalytic subunits are off, the protein
is off, allosteric activation
What is the third off switch of the AC pathway and what does it do? - Answers Phosphoprotein
phosphatase (PP), it catalyzes the removal of a phosphate by hydrolysis of phosphates that
were attached to proteins via PKA, adds water across the phosphoester linkage
What is a second messenger and give examples? - Answers A molecule inside cells that acts to
transmit signals from a receptor to a target, (cAMP, cGAMP, DAG, IP3, PIP3, Ca2+, NO nitric
oxide)
What is the fourth off point of the AC pathway? - Answers External inhibitory signal, reverts GTP
to GDP
What is the fifth off signal of the AC pathway? - Answers receptor desentization
Where are first messengers located? - Answers Outside of the cell
How many cAMP bind to each regulator in the AC pathway? - Answers 2
How many PPi are required to make 4 cAMP - Answers 4
