PHRM 836

Question 1

Which of the following best describes inter-cellular communication?
a) Cells responding only to mechanical signals
b) Cells communicating through chemical signals for coordination in multicellular organisms
c) Cells releasing enzymes to nearby cells to initiate responses
d) Cells relying solely on electric signals for communication

Answer 1

b) Cells communicating through chemical signals for coordination in multicellular organisms

Question 2

What is the main difference between signaling pathways and metabolic pathways?
a) Signaling pathways are slower and more stable than metabolic pathways
b) Signaling pathways focus on energy metabolism, while metabolic pathways focus on communication
c) Signaling pathways involve rapid, reversible changes, while metabolic pathways are more stable
d) Metabolic pathways do not involve any chemical changes in cells

Answer 2

Answer: c) Signaling pathways involve rapid, reversible changes, while metabolic pathways are more stable

Question 3

In paracrine signaling, the signals primarily affect which type of cells?
a) Distant cells across the organism
b) Cells that secreted the signals
c) Nearby target cells
d) Cells in the central nervous system only

Answer 3

c) Nearby target cells

Question 4

Which type of receptor binds hydrophilic ligands and is embedded in the cell membrane?
a) Intracellular receptors
b) GPCRs only
c) Cell surface receptors
d) Steroid receptors

Answer 4

c) Cell surface receptors

Question 5

Which of the following correctly matches a second messenger with its function?
a) Cyclic AMP (cAMP) - activates protein kinase A
b) IP3 - activates adenylate cyclase
c) DAG - releases calcium from the endoplasmic reticulum
d) Calcium ions (Ca2+) - only activates GPCRs

Answer 5

Answer: a) Cyclic AMP (cAMP) - activates protein kinase A

Question 6

What process involves the addition of a phosphate group to proteins, modifying their activity?
a) GTP binding
b) Phosphorylation
c) G protein deactivation
d) Ligand degradation

Answer 6

b) Phosphorylation

Question 7

Which statement best describes G protein-coupled receptors (GPCRs)?
a) They function as enzymes to break down ligands
b) They are intracellular receptors for hydrophobic ligands
c) They activate G proteins, leading to signaling cascades
d) They open ion channels upon ligand binding

Answer 7

c) They activate G proteins, leading to signaling cascades

Question 8

What is the role of KRAS in cell signaling?
a) It acts as a GTPase cycling between an active GTP-bound and inactive GDP-bound state
b) It directly activates calcium ion channels
c) It is a type of GPCR
d) It permanently remains in an active state

Answer 8

a) It acts as a GTPase cycling between an active GTP-bound and inactive GDP-bound state

Question 9

Which pathway is activated by Gq proteins?
a) cAMP pathway
b) Phospholipase C pathway
c) GTPase pathway
d) ATP synthesis pathway

Answer 9

b) Phospholipase C pathway

Question 10

What is a key feature of receptor tyrosine kinases (RTKs) when they bind to their ligand?
a) They dissociate into individual monomers
b) They dimerize and undergo autophosphorylation
c) They transport ligands directly into the nucleus
d) They release Ca2+ directly into the cytoplasm

Answer 10

b) They dimerize and undergo autophosphorylation

Question 11

Which mode of signaling involves direct contact between two cells for communication?
a) Autocrine signaling
b) Juxtacrine signaling
c) Endocrine signaling
d) Synaptic signaling

Answer 11

b) Juxtacrine signaling

Question 12

What role does cAMP play in cell signaling?
a) It binds directly to receptors to initiate signaling
b) It functions as a second messenger, activating protein kinase A
c) It inhibits GPCR activity
d) It promotes ligand degradation

Answer 12

b) It functions as a second messenger, activating protein kinase A

Question 13

How do phosphatases contribute to the regulation of cell signaling?
a) By removing phosphate groups, turning off signaling pathways
b) By adding phosphate groups to activate proteins
c) By binding to ligands to increase signaling duration
d) By blocking receptors from binding to ligands

Answer 13

a) By removing phosphate groups, turning off signaling pathways

Question 14

What happens to G protein-coupled receptors (GPCRs) after prolonged activation?
a) They degrade signaling ligands
b) They undergo receptor desensitization
c) They increase signal amplification indefinitely
d) They switch to autocrine signaling

Answer 14

b) They undergo receptor desensitization

Question 15

What is the function of IP3 (inositol triphosphate) in Gq protein signaling?
a) Activates protein kinase A (PKA)
b) Binds to GPCRs on the plasma membrane
c) Triggers the release of calcium ions from the endoplasmic reticulum
d) Degrades cAMP in the cytoplasm

Answer 15

c) Triggers the release of calcium ions from the endoplasmic reticulum

Question 16

Which of the following is a characteristic of nuclear receptors?
a) They are embedded in the plasma membrane
b) They typically bind hydrophilic ligands
c) They function as transcription factors in gene expression
d) They open ion channels directly

Answer 16

c) They function as transcription factors in gene expression

Question 17

What is the role of protein kinase C (PKC) in signaling pathways?
a) Activates GPCRs
b) Phosphorylates proteins in response to calcium and DAG
c) Releases calcium from the endoplasmic reticulum
d) Functions as a G protein

Answer 17

b) Phosphorylates proteins in response to calcium and DAG

Question 18

Which class of receptor is primarily involved in immune signaling through JAK-STAT pathways?
a) Receptor tyrosine kinases (RTKs)
b) GPCRs
c) Ion channel receptors
d) Cytokine receptors

Answer 18

d) Cytokine receptors

Question 19

Which protein family is frequently targeted in cancer therapies due to its role in cell proliferation and survival?
a) GPCRs
b) Ion channels
c) Receptor tyrosine kinases (RTKs)
d) G proteins

Answer 19

c) Receptor tyrosine kinases (RTKs)

Question 20

What is the function of the GTP-bound state of Gα subunits in the G protein cycle?
a) It inhibits adenylate cyclase activity
b) It keeps G proteins in an inactive state
c) It activates downstream effectors in the signaling pathway
d) It triggers the internalization of the receptor

Answer 20

c) It activates downstream effectors in the signaling pathway

Question 21

Which signaling molecule typically activates receptor tyrosine kinases (RTKs)?
a) Neurotransmitters
b) Growth factors
c) Calcium ions
d) cAMP

Answer 21

b) Growth factors

Question 22

What structural feature do all G protein-coupled receptors (GPCRs) share?
a) Three transmembrane domains
b) Seven transmembrane domains
c) Two extracellular domains
d) Multiple kinase-binding sites

Answer 22

b) Seven transmembrane domains

Question 23

What happens during the amplification step in a signaling pathway?
a) Ligands increase in concentration to boost signaling
b) A single receptor activation causes a cascade, leading to a large response
c) Second messengers are degraded to reduce the signal
d) The cell produces more receptors to enhance signaling

Answer 23

b) A single receptor activation causes a cascade, leading to a large response

Question 24

In the Gq signaling pathway, which enzyme does the Gα subunit activate?
a) Adenylate cyclase
b) Phospholipase C (PLC)
c) Protein kinase A (PKA)
d) Tyrosine kinase

Answer 24

b) Phospholipase C (PLC)

Question 25

What is a characteristic of autocrine signaling?
a) Signals affect distant target cells through the bloodstream
b) Cells respond to signals they themselves secrete
c) It requires direct contact between two cells
d) Signals only affect neurons

Answer 25

b) Cells respond to signals they themselves secrete

Question 26

Which second messenger is generated by the enzyme adenylate cyclase?
a) cAMP
b) DAG
c) IP3
d) Calcium ions

Answer 26

a) cAMP

Question 27

Which process helps in terminating a signal by degrading the ligand?
a) Endocytosis of receptors
b) GTP hydrolysis by G proteins
c) Ligand degradation
d) Protein phosphorylation

Answer 27

c) Ligand degradation

Question 28

Which type of receptor is responsible for the rapid response in neurons by allowing ions to flow across the membrane?
a) Cytokine receptors
b) Nuclear receptors
c) Ion channel receptors
d) GPCRs

Answer 28

c) Ion channel receptors

Question 29

What role does calmodulin play in signaling pathways?
a) Acts as a second messenger
b) Binds to calcium ions and modulates target proteins
c) Directly activates GPCRs
d) Facilitates ligand degradation

Answer 29

b) Binds to calcium ions and modulates target proteins