Lipids III

Question 1

In relation to the synthesis of phosphatidylcholine, what enzyme activates choline?

Answer 1

choline kinase

Question 2

After activation, what is done to activated phospho-choline?

Answer 2

Phosphocholine is transferred to CTP

Question 3

What enzyme transfers phosphocholine to CTP?

Answer 3

Phosphocholine cytidyltransferase

Question 4

What enzyme transfers CDP-choline to DAG?

Answer 4

choline phosphotransferase

Question 5

What is the alternative method of synthesizing phosphatidylcholine?

Answer 5

triple methylation of phosphatidylethanolamine

Question 6

What is the first step in the synthesis of phosphatidylethanolamine?

Answer 6

Ethanolamine is activated by phosphorylation and then transferred to CTP

Question 7

What is the function of ethanolamine phosphotransferase?

Answer 7

to transfer CDP-ethanolamine to diacylglycerol

Question 8

What does ethanolamine phosphotransferase produce?

Answer 8

PE

Question 9

What is the main enzyme responsible for the synthesis of phosphatidylserine ?

Answer 9

phosphatidylserine synthase

Question 10

What is the function of phosphatidylserine synthase?

Answer 10

to replace the head group of PE with a serine

Question 11

How does the synthesis of phosphatidylinositol differ from the other membrane phospholipids?

Answer 11

In PI, it is the DAG that is activated by binding to CTP

Question 12

What is CDP-diacylglycerol formed from?

Answer 12

CTP and phosphatidic acid

Question 13

Where is cardiolipin located?

Answer 13

Inner mitochondrial membrane

Question 14

Essentially, what is cardiolipin?

Answer 14

A phosphatidic acid dimer connected by a glycerol bridge

Question 15

What is the function of cardiolipin?

Answer 15

to aid in the folding of inner mitochondrial membrane electron transport complexes

Question 16

What two diseases feature a decline in the level of cardiolipin?

Answer 16

Alzheimer’s and Parkinson’s

Question 17

What is the outer leaflet of the plasma membrane rich with?

Answer 17

choline-containing lipids PC and sphingomyelin

Question 18

What is the inner leaflet of the plasma membrane rich with?

Answer 18

PE and negatively charged lipids such as PS

Question 19

What will happen to a cell with PS expressed on its outer surface?

Answer 19

destroyed by macrophages

Question 20

What carbons on a TAG are acted on by which phospholipases?

Answer 20

C1 = PLA1

C2 = PLA2

C3 = PLC (removes phosphate group)

Question 21

How are freshly synthesized phospholipids similar?

Answer 21

A saturated or oleic acid at C1 and an unsaturated FA at C2

Question 22

What leaflet, inner or outer, is arachidonic acid contained?

Answer 22

inner

Question 23

What fatty acid is arachidonic acid synthesized from? Why is this?

Answer 23

linoleic acid. Arachidonic has double bonds in the distal part of it and must be synthesized from an essential FA.

Question 24

What phospholipase is responsible for cleaving arachidonic acid from its membrane lipid?

Answer 24

PLA2

Question 25

What enzyme is responsible for incorporating arachidonic acid into its phospholipid?

Answer 25

phospholipase A2 acyltransferase

Question 26

What are the three main functions of prostoglandins?

Answer 26

1. vasodilation during inflammation 2. uterine contractions 3. inhibit platelet aggregation

Question 27

How do corticosteroids inhibit the production of prostaglandins?

Answer 27

directly inhibiting the function of PLA2

Question 28

What are leukotrienes synthesized from?

Answer 28

arachidonic acid

Question 29

What type of reaction stimulates leukotriene synthesis?

Answer 29

lipoxygenase

Question 30

What is the main function of LTC4 and LTD4?

Answer 30

to promote smooth muscle contraction in blood vessels, airways and the intestine

Question 31

What compounds make up the slow reacting substance of anaphylaxis (SRS-A)?

Answer 31

LTC4 and LTD4

Question 32

What type of (unusual) bond do plasmalogens possess?

Answer 32

fatty alcohol in an ether linkage

Question 33

How does plasmalogen synthesis begin?

Answer 33

With the transfer of an acyl group to the C1 of DHAP

Question 34

What is the 2nd, and arguably most important, step of plasmalogen synthesis?

Answer 34

The acyl group on C1 is then exchanged for a fatty alcohol

Question 35

What is the 3rd step of plasmalogen synthesis?

Answer 35

acyl group from acyl-CoA is transferred to the C2

Question 36

What is the final step in plasmalogen synthesis?

Answer 36

addidtion Choline (from CDP-choline) at C3

Question 37

In plasmalogen synthesis, where does the induction of the ether linkage take place?

Answer 37

peroxisomes

Question 38

What are sphingolipids derived from?

Answer 38

sphingosine

Question 39

What common phospholipid backbone do sphingolipids not contain?

Answer 39

glycerol

Question 40

In the first step of sphingolipid synthesis, what two molecules condense? What molecule is formed?

Answer 40

serine and palmitoyl-CoA. Dihydrosphingosine

Question 41

What is the second step of sphingolipid synthesis?

Answer 41

attachment of an acyl group (often behenyl-CoA, C22) to the amino group of dihydrosphingosine

Question 42

What product is formed at the end of the 2nd step of sphingolipid synthesis?

Answer 42

dihydroceramide

Question 43

What reduction equivalent is given off when dihydroceramide is oxidized to ceramide?

Answer 43

FADH

Question 44

What is the function of ceramide regarding sphingolipid biosynthesis?

Answer 44

lipid backbone

Question 45

What must happen to ceramide to become a sphingolipid?

Answer 45

transfer of a head group to C1

Question 46

What does a transfer of a phosphocholine to C1 result with?

Answer 46

sphingomyelin

Question 47

What does a transfer of a glucose or galactose to C1 result with?

Answer 47

cerebroside

Question 48

What does transfer of a sulfate group to cerebrosides result in?

Answer 48

sulfatide

Question 49

What does the transfer of several neutral sugars to ceramide result with?

Answer 49

globosides

Question 50

What does the transfer of several sugars, one of which is NANA/sialic acid to ceramide result with?

Answer 50

gangliosides

Question 51

What is cardiolipin located?

Answer 51

inner mitochondrial membrane

Question 52

Essentially, what is cardiolipin?

Answer 52

two phosphatidic acids linked by a glycerol bridge

Question 53

What is the outer leaflet rich in?

Answer 53

choline containing lipids and sphingomyelin

Question 54

What is the inner leaflet rich in?

Answer 54

PS and PE

Question 55

stress induces what inner leaflet component to translocate to the outer leaflet?

Answer 55

PS

Question 56

How are freshly synthesized lipids similar?

Answer 56

saturated or oleic acid at C1 desaturated acid at C2

Question 57

What is arachidonic acid synthesized from?

Answer 57

linoleic acid

Question 58

What is the function of thromboxane synthase?

Answer 58

to produce thromboxanes from PGH2

Question 59

What are leukotrienes synthesized from?

Answer 59

arachidonic acid

Question 60

What type of reaction initiates leukotriene synthesis?

Answer 60

lipoxygenase

Question 61

What is the critical step in the synthesis of plasmalogens? Where does this occur?

Answer 61

ether linkage at C1. Peroxisomes

Question 62

What are sphingolipids synthesized from?

Answer 62

Serine and palmitoyl-CoA

Question 63

The transfer of phosphocholine to ceramide yields what?

Answer 63

sphingomyelin

Question 64

Trasfer of glucose or galactose to ceremide yields what?

Answer 64

cerebroside