Lipid Signaling

Question 1

juxtacrine signaling

Answer 1

communication across a cell junction connecting intracellular compartments of 2 cells
with small molecules like Na+ and K+

Question 2

Endocrine

Answer 2

cells targeting a distant cell through the bloodstream
hormone ligands bind to cells only with appropriate receptors

Question 3

Paracrine

Answer 3

cell targeting a nearby or adjacent cell

Question 4

autocrine

Answer 4

a cell signal targeting itself

Question 5

pheromones

Answer 5

substances secreted by an individual and received by another individual of the same species

Question 6

3 categories of lipids

Answer 6

membrane, storage and active
membrane and storage are passive functions, used until oxidized essentially

Question 7

categories of active lipids

Answer 7

glycerophospholipids, sphingolipids, sterols, prenol lipids and eicosanoids

Question 8

glycerophospholipid examples

Answer 8

phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol triphosphate (PIP3),

Question 9

sphingolipids examples

Answer 9

sphingolipids: sphingomyelin, ceramides
glycosphingolipids: , gangliosides (oligosaccharide head), cerebrosides

Question 10

sterol lipids

Answer 10

sterols: cholesterol, progesterone, testosterone, estradiol, cortisol, aldosterone, bile acids (hormones)
act through nuclear receptors and affect cellular transcription
produced by pituitary based on signal from hypothalamus

Question 11

PIP2 function

Answer 11

phosphatidylinositol 4,5-bisphosphate
acts as a reservoir of signaling molecules
ex. PIP2 –> IP3 via phospholipase C in GPCR beta-adrenergic pathway
ex. PIP2 –> PIP3 via PI3Kinase phosphorylation in insulin RTK pathway

Question 12

IP3 function and calmodulin pathway

Answer 12

signaled from b-adrenergic receptor epinephrine signaling
1. created from phospholipase C hydrolyzing PIP2
2. IP3 binds to ligand gated Ca2+ channel in ER, releasing Ca2+ into cytoplasm
3. Ca2+ activates calmodulin, which activates phosphorylase kinase
4. Phosphorylase kinase activates glycogen phosphorylase stimulating breakdown of glycogen into glucose

Question 13

sphingomyelin structure

Answer 13

ceramide + phosphocholine
insulates nerve axons

Question 14

lipid rafts

Answer 14

stabilized and modulated by ceramides
influence membrane fluidity and protein trafficking

Question 15

markers of blood groups

Answer 15

sugar heads on glycosphingolipid oligosaccharides indicate type of glycosyltransferases
O antigen - no glycosyltransferase (base oligo saccharides structure)
A antigen - N-acetylgalactosamine sugar
B antigen - galactose sugar

Question 16

Eicosanoids

Answer 16

paracrine hormones derived from eicosapentanoic acid and arachadonic acid
arachadonate is released from glycerophospholipids by phospholipase A2 (second acyl)
act through GPCR signaling pathways

Question 17

classes of eicosanoids

Answer 17

prostaglandins, thomboxanes, leukotrienes, lipoxins

Question 18

Prostaglandins function

Answer 18

smooth muscle contraction during labor and periods
regulates blood flow, body temp, reproductive cycle and sleep-wake cycle
regulates responsiveness in some tissues to epinephrine and glucagon
inflammatory and cause pain

Question 19

Thromboxanes functions

Answer 19

produced by platelets to form blood clots, and reduce blood flow to site of a clot

Question 20

Leukotrienes function

Answer 20

Airway smooth muscle contraction
Overproduction leads to asthmatic attacks
first found in leukocytes

Question 21

Lipoxins functions

Answer 21

Anti-inflammatory signals
Low dose asprin stimulates production of lipoxin, which is why that was prescribed for awhile for CVD

Question 22

How do NSAIDs work?

Answer 22

they inhibit cyclooxygenase enzymes (COX 1 and 2) which lead to production of prostaglandin E2 and thromboxanes A2

Question 23

How does prednisone work?

Answer 23

Inhibits phospholipase A2, which inhibits production of leukotrienes
used for asthma, arthritis, lupus, organ transplants

Question 24

prenol lipids examples

Answer 24

prenols: farnesol, geraniol, retinol, ubiquinone, tocopherols (vitamin E)

Question 25

Vitamin D as a pre-hormone

Answer 25

7-dehydrocholesterol in skin + UV light –> cholecalciferol (D3)
Cholecalciferol –> via liver and kidney 1,25 dihydroxyvitamin D3 (active form) called Calcitriol
Calcitriol regulates Ca absorption and excretion, Ca storage in bone
Rickets - vitamin D3 deficiency leading to softening of bones in children (bowed legs)
Signals through VDR receptors on many tissues

Question 26

Vitamin A functions
receptors

Answer 26

prenol acts as hormone and pigment
deficiency leads to night blindness, growth retardation, dry skin
retinal binds opsin to form rhodopsin pigment in photoreceptor of eye
receptors involved: Retinoic acid receptor RAR, Retinoid X Receptor RXR

Question 27

Vitamin A conversion pathway

Answer 27

Beta-carotene –> all-trans retinal
All-trans retinal –> all-trans retinoic acid –> hormonal signal
All-trans retinal –> all-trans retinol (animal form) –> cis-retinal –> all-trans retinal –> neuronal signaling in vision

Question 28

Tocopherols function

Answer 28

Vitamin E, type of prenol lipid
act as a cofactor to react with O2 free radicals and product membranes

Question 29

Vitamin K function
Warfarin

Answer 29

type of prenol lipid
acts as a cofactor to prothrombin converting soluble fibrinogen into insoluble fibrin
Warfarin inhibits prothrombin

Question 30

Ubiquinone and Plastoquinone

Answer 30

Both prenol lipids and cofactors
Ubiquinone: electron carrier in mitochondria
Plastoquinone: electron carrier in chloroplasts

Question 31

Phosphorylase kinase

Answer 31

phosphorylase activity involves cleaving a glycosidic bond by substituting it with a phosphate
phosphorylase kinase phosphorylates a phosphorylase enzyme