Lecture 4 (Cell Signaling I)

Question 1

Ligand

Answer 1

• signaling molecule = start of signaling pathway
• binds to receptor

Question 2

Secondary Messengers

Answer 2

• intracellular signaling molecules
• ex. Ca++

Question 3

Ca++

Answer 3

• important 2ndary messenger
• conc inside cell = very low by Ca++ ATPASE
• stored in ER
• binds to protein ex. calmodulin -> other proteins

Question 4

Polar Signaling Molecule

Answer 4

• bind to membrane receptor

Question 5

Non Polar Signaling Molecule

Answer 5

• diffuse across membrane + bind intracellular receptor: nuclear receptors

Question 6

Nuclear Receptors

Answer 6

• intracellular receptor
• ligand-activated transcription factor
• receptor -> nucleus -> bind DNA -> change gene expression

Question 7

Ligand Gated Ion Channel (Iontropic Receptors)

Answer 7

• fastest chemical signaling
• fast synaptic transmission
• ligand bind -> open channel -> ion flow -> memb pot change
• ex. Nicotinic Acetylcholine Receptor

Question 8

G - protein coupled receptors

Answer 8

• mediate slow synaptic transmission
• most common type
• 7 transmembrane domains
• receptor coupled -> heterotrimeric G protein
• Activation -> GDP release + replace w/ GTP -> G alpha dissociation -> type f G alpha = transmission pathway

Question 9

Gs

Answer 9

• G alpha subunit -> stimulate adenylyl cyclase -> catalyze formation of cAMP (from ATP) -> activate (PKA) [cAMP bind to PKA reg subunit] -> PKA cat subunits phosphorylate other protein

Question 10

GPCR Signal Termination

Answer 10

• G- alpha inherent GTPase activity
  
  • hydrolyze GTP -> GDP = inactive protein
• Phosphodiesterase
  
  • breaks down cAMP
• Phosphates
  
  • dephosphorylate proteins active by PKA
• Cholera Toxin
  
  • inactivate GTPase of G-alpha = ecessive cAMP -> PKA -> CFT active -> fluid loss

Question 11

cAMP and G, olf

Answer 11

• can act as ligand
• G,alpha subunit olf-> adenylyl cyclase on ATP = cAMP ligand
• opens cyclic nucleotide-gated channel
  
  • depolarize olfactory neuron