chapter eleven

Question 1

eukaryotic example of single-celled organisms communicating

Answer 1

Baker’s yeast - uses chemical signaling when producing sexually, then shape/fuse toward each other
- 2 sexes: a and alpha

Question 2

prokaryotic example of single-celled organisms communicating

Answer 2

Bacterial cells - secrete signaling molecules, cell density monitored by quorum sensing, biofilms

Question 3

biofilms

Answer 3

aggregation of bacterial cells attached to surface by molecules secreted by cells
- only after cells have reached certain density
- protects and provides nutrition

Question 4

need for cell communication in eukaryotic multicellular organisms

Answer 4

embryonic development, immune response, adult stem pop. maintenance

Question 5

external signals (primary messenger)

Answer 5

• steroid molecules, proteins/glycoproteins, dipeptides, amino acids, gases
• lead to response within cell

Question 6

signal transduction pathway

Answer 6

sequence of changes in series of different molecules
1. signal reception
2. signal transduction
3. cellular response

Question 7

examples of local distance signaling

Answer 7

paracrine, synaptic, autocrine

Question 8

examples of long distance signaling

Answer 8

endocrine

Question 9

paracrine signaling

Answer 9

signals/molecules only travel short distance to neighboring cells
- local regulators
- fast (just into ECF)
- handful of target cells
- growth factors

Question 10

synaptic signaling

Answer 10

nerve cell releases neurotransmitter into synapse of target cell
- very targeted
- like subset of paracrine
- super fast (1 cell to 1 target across synaptic cleft)

Question 11

autocrine signaling

Answer 11

cell secretes signal, but cell has receptors for own signal
- subset of paracrine

Question 12

endocrine signaling

Answer 12

hormones secreted into fluids, only bounded by and affect some cells
- travels through blood
- slow-ish
- large number of possible target cells, but can only respond if it has receptors

Question 13

what signaling molecules use receptors in the cytoplasm?

Answer 13

steroids and gases
- can diffuse through membrane
- hydrophobic/smal molecules

Question 14

what signaling molecules use receptors on the plasma membrane?

Answer 14

proteins, dipeptides, amino acids
- most water-soluble molecules

Question 15

3 stages of cell signaling

Answer 15

1. reception - target cell receives signaling molecule, which binds to receptor protein
2. transduction - protein receptor changed
3. response - transducer signal triggers cellular response

Question 16

signal reception

Answer 16

signaling molecule acts as ligand (specifically binds to another molecule)

Question 17

examples of plasma membrane receptors

Answer 17

1. G-protein coupled receptors
2. receptor tyrosine kinases
3. ligand-gated ion channels

Question 18

G-protein coupled receptors (GPCR)

Answer 18

• 7 transmembrane alpha helices, provide binding sites for signaling molecule and G protein
• G protein binds to GDP when inactive and GTP when active
• GTP + G-protein go to enzyme

Question 19

receptor tyrosine kinases

Answer 19

• ligand binding pushes them together to form dimer
• dimer autophosphorylates, transferring P group from ATP to another protein
• an activate 10+ different transduction pathways

Question 20

ion-channel receptors (ligand-gated ion channels)

Answer 20

after the ligand binds, channel opens/closes to allow/block specific ions
- ions will only go through w/ gradient

Question 21

ex. of steroid hormones

Answer 21

aldosterone, testosterone, progesterone, estrogen

Question 22

ex. of signaling gases

Answer 22

NO, CO

Question 23

what happens to cytoplasm receptors upon binding

Answer 23

active form of receptor protein enters nucleus and turns on specific genes
- acts as transcription factor for mRNA
- both receptor and transducer

Question 24

what is being transducer?

Answer 24

proteins

Question 25

what does protein phosphorylation and dephosphorylation do?

Answer 25

transduction and shape change of proteins

Question 26

kinases

Answer 26

phosphorylation - transfer P from ATP to protein - can act on each other to produce phosphorylation cascade

Question 27

phosphatases

Answer 27

dephosphorylation - remove phosphate groups from proteins, inactivating kinases - turn off signal transduction pathway when initial signal no longer present - make kinases available for reuse

Question 28

second messengers

Answer 28

small, nonprotein, water-soluble molecules or ions used in pathways

Question 29

2 main types of second messengers

Answer 29

1. cyclic AMP 2. calcium ions

Question 30

cAMP

Answer 30

- made from ATP - catalyzed by adenylyl cyclase - binding of signal molecule to receptor (sometimes GPCR)

Question 31

calcium ions

Answer 31

- cytosol concentrations of Ca2+ increase - transported out of cell and into ER by protein pumps - both GPCR/RTK

Question 32

where are calcium ion concentrations kept low?

Answer 32

in the cytosol

Question 33

inositol triphosphate

Answer 33

- hydrolysis of PIP2 - soluble - generated by phospholipase C - diffuses through cytosol and binds to IP3 gated calcium channel in ER membrane to open it

Question 34

diacylglycerol

Answer 34

- hydrolysis of PIP2 - insoluble - generated by phospholipase C - stays within PM and goes to other pathways

Question 35

what second messengers lead to Ca2+ release?

Answer 35

inositol triphosphate and diacylglyercol - produced by cleavage of certain kind of phospholipid in membrane

Question 36

why are there different cellular responses to signaling molecules?

Answer 36

different collections of proteins

Question 37

gene regulation via activated transcription factor controlling

Answer 37

- synthesis of mRNA, which will be translated into specific proteins

Question 38

gene regulation via regulating activity of proteins

Answer 38

- outside nucleus - uses both second messengers and kinases - epinephrine -> breakdown of glycogen

Question 39

scaffolding protein

Answer 39

large relay protein to which several other relay proteins are attached

Question 40

what does termination of the signal depend on?

Answer 40

reversible ligand binding - external concentration of ligands falls, fewer receptors bound, unbound receptors revert to inactive form

Question 41

apoptosis

Answer 41

type of controlled/programmed cell suicide

Question 42

how does apoptosis occur

Answer 42

DNA and organelles chopped, cell shrinks and becomes lobed, parts packaged in vesicles and digested by scavenger cells

Question 43

what is apoptosis essential for

Answer 43

embryonic development, metamorphosis, maintenance, nervous system, immune system

Question 44

external signals for life/death of cells

Answer 44

come from other cells

Question 45

internal sources for life/death signals

Answer 45

series of protein-protein interactions, nucleus (DNA) damage, ER (excessive protein misfolding)

Question 46

blebs

Answer 46

membrane-bound cell fragments in apoptosis - cytoskeleton breaks up and forms bulges

Question 47

main proteases of apoptosis

Answer 47

caspases

Question 48

secondary messenger

Answer 48

internal, small, non-enzymatic, usually soluble