Chapter 11: Cell Signaling

Question 1

Mating factors

Answer 1

a and α factors of yeast cells. when exposed a pair of cells of the opposite type fuse into new a/α cell

Question 2

Signal transduction pathway

Answer 2

Signal binds to receptor and is transduced (changed) into response

Question 3

Quorum sensing

Answer 3

Bacteria sense concentration of signaling molecules to monitor local density of cells

Question 4

Local signaling

Answer 4

Signaling for nearby cells
- cell junctions
- cell cell recognition (surface molecules)

Question 5

Local regulators

Answer 5

Signaling molecules for short distances
- growth factors (growth/division)

Question 6

Paracrine signaling

Answer 6

Numerous cells simultaneously recieve/respond to signaling molecules produced by a single nearby cell

Question 7

Synaptic signaling

Answer 7

Electrical signal along nerve cell triggers secretion of neurotransmitters, which diffuse across the synapse to the target cell

Question 8

Hormones

Answer 8

Chemicals for long distance signaling

Question 9

Endocrine signaling

Answer 9

Specialized endocrine cells release hormones which travel through the circulatory system to target cells

Question 10

Plant hormones

Answer 10

Sometimes travel in vessels but mostly move through cells or diffuse through the air as gas

Question 11

Epinephrine

Answer 11

Hormone that stimulates breakdown of glycogen

Question 12

Glycogen breakdown

Answer 12

Releases glucose 1-phosphate, which is converted to glucose 6-phosphate. Then used by liver/muscle cell for energy production, or stripped of phosphate and released into blood as glucose

Question 13

Glycogen phosphorylase

Answer 13

Cytosolic enzyme activated by epinephrine through a series of steps (plasma membrane is necessary)

Question 14

Reception

Answer 14

Detection; Signal binds to receptor protein on target cell

Question 15

Transduction

Answer 15

Converts signal to a form that causes a specific cellular response

Question 16

Signal transduction pathway

Answer 16

Sequence of changes in a series of different molecules

Question 17

Response

Answer 17

Cellular activity caused by signal

Question 18

Ligand

Answer 18

Molecule that specifically binds to another molecule. Binding generally causes a shape change in receptor

Question 19

GPCR

Question 20

G protein

Question 21

GTPase enzyme

Question 22

GPCR pathway

Question 23

Receptor tyrosine kinase

Answer 23

Plasma membrane receptor that attaches phosphate to tyrosine because of ligand. Can activate 10+ transduction pathways/results -> abnormal ones cause many cancers

Question 24

RTK pathway

Question 25

Ligand gated ion channel

Answer 25

Membrane receptor with a ion channel that opens/closes if bound to ligand.

Question 26

Cell surface receptors

Answer 26

GPCR, RTK, ligand gated ion channels. 30% of all proteins. Flexible and unstable (difficult for X-ray crystallography)

Question 27

Intracellular receptors

Answer 27

In nucleus or cytoplasm. Signaling molecules must be small and/or hydrophobic. - transcription factors

Question 28

Relay molecules

Answer 28

Relay a signal from receptor to response

Question 29

Protein kinase

Answer 29

Enzyme that transfers phosphate from ATP to protein - most act on other proteins not themselves - serine/threonine are often phosphorylated

Question 30

Phosphorylation cascade

Answer 30

Pathway of protein phosphorylation

Question 31

Protein Phosphatase

Answer 31

Enzyme catalyze removal of phosphate from protein (dephosphorylation)

Question 32

Second messengers

Answer 32

Small, non protein, water soluble molecules in signaling pathways

Question 33

Adenyl Cyclase

Answer 33

Converts ATP to cyclic AMP in response to extracellular signal. Can greatly increase cytosolic concentration of cAMP

Question 34

cAMP

Answer 34

Important second messenger. Activated by epinephrine and many other hormones/signals. Included in G protein, GPCR, and protein kinase pathways. High levels of cAMP activates protein kinase A.

Question 35

Protein kinase A

Answer 35

Serine/threonine kinase which phosphorylates a variety of other proteins

Question 36

Phosphodiesterase

Answer 36

Converts cAMP to AMP

Question 37

Cholera

Answer 37

Cholera toxin permanently activates G protein involved in salt/water regulation by stopping it from hydrolyzing GTP to GDP. G protein continually activates adenyl cyclase, and resulting high concentration of cAMP causes lots of salt and water (osmosis) to be released from intestinal cells.

Question 38

Ca 2+

Answer 38

Important second messenger Functions: muscle cell contraction, secretion of certain substances, cell division, etc. -low cytosolic concentration (actively transported into ER, outside the cell, sometimes to mitochondria/chloroplasts) - signal increases cytosolic concentration of ca 2+ (usually through ER)

Question 39

IP3 (inositol triphosphate)

Answer 39

Second messenger involved in calcium release. Diffuses through cytosol and binds to IP3 gated channel on ER membrane, causing it to open (calcium is released to cytosol)

Question 40

DAG (diacylglycerol)

Answer 40

Second messenger involved in calcium release

Question 41

Phospholipase C

Answer 41

Cleaves plasma membrane phospholipid PIP2 into IP3 and DAG

Question 42

Calcium release pathway

Answer 42

1. Signal activates receptor 2. Receptor activates phospholipase C 3. Phospholipase C forms IP3 4. IP3 binds to ER membrane protein 5. Calcium released from ER

Question 43

Scaffolding proteins

Answer 43

Large relay proteins that attach to several other relay proteins - can permanently hold together signaling pathway proteins at synapses

Question 44

Apoptosis

Answer 44

Controlled cell suicide. DNA and organelles are cut up. Cell shrinks and becomes lobed, packaged into vesicles. Scavenger cells digest vesicles.

Question 45

C. Elegans apoptosis

Answer 45

1. Ced-9 protein in outer mitochondrial membrane inhibits Ced-3 and ced-4. 2. Death signal inactivated ced-9 3. Activated ced-3 (protease) and ced-4 activates nucleuses and proteases

Question 46

Caspases

Answer 46

Main proteases of apoptosis