Chapter 9 Exam 3

Question 1

what happens to the signaling peptide at low population density

Answer 1

the concentration of the signaling peptide is too low to stimulate DNA uptake by bacteria

Question 2

what happens in pneumococcal signaling

Answer 2

1. the peptide signaling molecule binds to the receptor on the cell surface
2. when enough peptide is bound a signal is relayed by a signal transduction to the. nucleic region of the bacterial cell
3. genes are turned on that express proteins involved in DNA uptake from the environment
4. when the density of bacteria is low the signal falls below its critical threshold and the gene expression is turned off

Question 3

what is contact dependent signaling

Answer 3

communication through direct physical contact, without a chemical signal that diffuses or circulates through an external medium

Question 4

what is notch expressing cells

Answer 4

supporting glial cells

Question 5

what are delta expressing cells

Answer 5

cell develops into a neuron

Question 6

what signaling molecules bind to cell surface receptors

Answer 6

polar signaling molecules

Question 7

what signaling molecules bind to intracellular receptors

Answer 7

small non polar signaling molecules

Question 8

what do kinases do

Answer 8

phosphorylate which turns proteins on

Question 9

what do phosphates do

Answer 9

dephosphorylate which turns proteins off

Question 10

what are the 3 kinds of receptor proteins

Answer 10

• GPCRs
• receptor kinases
• ligand gated ion channels

Question 11

what are the 2 second messengers involved with GPCRs

Answer 11

Ca2+ and cAMP

Question 12

what do second messengers do

Answer 12

amplify the signal

Question 13

what happens in GPCR activation

Answer 13

alpha subunit binds GTP and activates adenylyl cyclase, adenylyl cyclase takes ATP and makes cAMP which activates PKA that phosphorylates proteins

Question 14

how do you reset the cellular response in GPCRs

Answer 14

1. alpha subunit is only bound for short amount of time then gets GDP back and rebinds to beta and gamma
2. a phosphodiesterase shuts off cAMP to stop activating PKA. when cAMP turns off it goes back to AMP
3. phosphates remove phosphate groups from target proteins that were phosphorylated by PKA

Question 15

what happens in receptor kinases

Answer 15

• ligands bind and bridge 2 kinases which then phosphorylate each other
• they come together and take a phosphate from ATP and phosphorylate each other
• then they phosphorylate other proteins

Question 16

what is dimerization

Answer 16

when subunits come together into a single protein complex

Question 17

what happens in RAS signaling

Answer 17

-controls when a cell divides and receives a growth signal
-it’s like a G protein but isn’t one
activated when GDP turns into GTP

Question 18

what happens in the Map kinase pathway

Answer 18

activated Ras signaling protein activates a kinase which activates another kinase and goes to the nucleus, amplifying the signal as it gets passed

Question 19

what do receptor kinases do in life

Answer 19

cancer and wound healing. some prevent Ras from convert GTP to GDP causing protein to always be on

Question 20

what cell signaling issues cause cancer

Answer 20

increased number receptors, overproduction signaling molecule, ras mutations