exam 2 cellular communication

Question 1

how do cells communicate with each other

Answer 1

receptors, which bind to signal molecule ligands

Question 2

what is the outcome of signaling

Answer 2

rapid changes in protein function snd/or slower changes in gene expression

Question 3

how do hydrophobic ligands cross membranes

Answer 3

easily to activate intracellular receptors

Question 4

how do hydrophilic ligands cross membranes

Answer 4

they bind to cell-surface transmembrane receptors

Question 5

what does signal transduction from cell-surface receptors require

Answer 5

the activation or generation of second messengers, which transmit the signals from the cell surface to the effectors

Question 6

what are the three basic modes of signaling

Answer 6

• ion channels
• enzyme-coupled receptors
• G-protein-coupled receptors

Question 7

what are the three steps of signaling

Answer 7

reception, transduction, response

Question 8

what signaling can secreted molecules do

Answer 8

paracrine, endocrine, and synaptic siganling

Question 9

what is paracrine signaling

Answer 9

act as local mediators, affecting only cells in the immediate environment of the signaling cell

Question 10

what is endocrine signaling

Answer 10

travel long distances through the bloodstream to act on distant targets

Question 11

what is synaptic signaling

Answer 11

travel via axons

Question 12

what is autocrine signaling

Answer 12

a cell secretes signal molecules that can bind back to its own receptors

Question 13

when is autocrine signaling useful

Answer 13

in positive or negative feedback loops - allow cells to amplify the signal or make one that is self-limited

Question 14

what is contact-dependent siganling

Answer 14

signal molecules remain bound to the surface of the signaling cell and influence only cells that contact it

Question 15

what can signaling molecules do/alter

Answer 15

slowly or rapidly alter the function of a target cell or flip the protein on or off or change the amount of protein to alter protein function

Question 16

can signals work together

Answer 16

yes and cells can be programmed to respond to one combination of signals by growth/division, and these can promote survival

Question 17

what happens when cells are deprived of their signals

Answer 17

they activate apoptosis

Question 18

how do cellular responses vary

Answer 18

according to the receptor proteins the cell has and the intracellular signaling machinery the cell uses to interpret them

Question 19

what are morphogens

Answer 19

molecules that diffuse out from signaling centers in developing tissues, creating a morphogen concentration gradient

Question 20

how do cells adopt different fates from each other

Answer 20

depending on their position in the gradient. in this way layers of cells develop, each with a different function based on their concentration

Question 21

how can concentration amount be useful

Answer 21

can determine where molecules are in the cell based on it

Question 22

what are the types of signals

Answer 22

mechanical, light, heat, chemical

Question 23

what forms do chemical stimuli come in

Answer 23

amino acids, small peptides, proteins, nucleotides, steroids, fatty acid derivatives, dissolved gasses

Question 24

what does exocytosis do

Answer 24

signal molecules are secreted from the signaling cell into the extracellular space

Question 25

how are some cells exposed to extracellular space

Answer 25

- exposed to the extracellular space while remaining tightly bound to the signaling cell's surface - released by diffusion through the plasma membrane

Question 26

what happens with lipid soluble signaling molecules

Answer 26

they can simply diffuse across the plasma membrane

Question 27

what signal molecules are lipid soluble

Answer 27

steroid hormones and gaseous signaling molecules

Question 28

what happens with steroid hormones

Answer 28

they travel to their target cells via carrier proteins and bind to intracellular receptors, which can either be cytosolic or nuclear

Question 29

what family are receptors for steroid hormones a part of

Answer 29

the nuclear receptor subfamily

Question 30

prior to ligand binding, what do receptors bind to

Answer 30

an inhibitory protein and are inactive

Question 31

what does ligand binding cause

Answer 31

a conformational change in the receptor, which causes an inhibitory protein to dissociate

Question 32

what does a conformational change expose

Answer 32

exposes a site which binds to the promoter region upstream of a specific targeted gene

Question 33

what occurs with transcription of a targeted gene

Answer 33

it's then increased, producing specific proteins leading to changes in cell behavior

Question 34

what happens to hydrophilic/lipid insoluble signals

Answer 34

they cannot cross cell membranes and they must bind to sites on cell surface receptors

Question 35

what are ligand-gated ion channels

Answer 35

binding of ligands to the channel causes it to open and allows specific ions to flow through

Question 36

what are enzyme coupled receptors

Answer 36

activate an enzyme when activated by a signal molecule binding to a receptor

Question 37

what are G-protein-coupled receptors

Answer 37

activation of receptor causes a change in GTP vs GDP binding of a switch protein, which turns downstream enzymes on or off

Question 38

what are ion-channel-coupled receptors involved in

Answer 38

synaptic signaling - opened/closed by neurotransmitters

Question 39

what do ion-channel-coupled receptors do

Answer 39

alter ion permeability to cause membrane potential changes

Question 40

what family are G-protein-coupled receptors from

Answer 40

large family of multi-pass transmembrane proteins

Question 41

what do G-protein-coupled receptors indirectly regulate

Answer 41

the activity of a nearby target protein in the membrane

Question 42

what do G-protein-coupled receptors contain

Answer 42

a GTP binding protein complex that acts as the middle man between an activated receptor and its target

Question 43

what do enzyme-coupled receptors function as

Answer 43

protein kinases

Question 44

what do enzyme-coupled receptors indirectly regulate

Answer 44

the activity of a nearby target protein that is in kinase cascade

Question 45

what does the kinase cascade allow for

Answer 45

rapid amplification of signals

Question 46

what carriers a first messenger signal across the plasma membrane

Answer 46

cell-surface receptors

Question 47

what do second messengers do

Answer 47

they are a combination of activated enzymes and small intracellular molecules that amplify the signal and spread it through the cell

Question 48

what regulates a cell's responses

Answer 48

activated effector proteins

Question 49

what are molecular switches activated by

Answer 49

- kinases/phophatases: phosphorylation/dephosphorylation | - GTPases/GTP-binding proteins

Question 50

what forms protein complexes called signaling complexes

Answer 50

enzymes activated by a receptor protein

Question 51

what do signaling complexes regulate

Answer 51

speed, efficiency, specificity of a cellular response

Question 52

how can signaling complexes be organized

Answer 52

organized around a scaffold protein, assembled following receptor activation or on phosphorylated lipids

Question 53

what do enzyme-coupled receptors interact with

Answer 53

receptor tyrosine kinases, which dimerize and phosphorylate themselves upon ligand binding

Question 54

what do receptor tyrosine kinases allow for

Answer 54

recruitment of other ligands to bind and increases substrate range of kinase to phosphorylate other targets

Question 55

what activates the GTPase signaling protein, Ras

Answer 55

tyrosine kinase, which covalently attaches to lipid anchor (inner leaflet of plasma membrane)

Question 56

what does Ras initiate

Answer 56

a cascade of phosphorylation events mediated by a group of MAP kinases

Question 57

when bound to a ligand, what does a G-protein-coupled receptor do

Answer 57

releases GDP and binds to GTP

Question 58

when not bound to a ligand, what does a G-protein-coupled receptor do

Answer 58

it's bound to GDP

Question 59

what is cAMP

Answer 59

a common second messenger