Membrane Lipids

Question 1

lipids and cancer

Answer 1

• cancerous cells need to make a lot of membrane lipid in order to divide rapidly
• upregulate citratelyase and down regulate FA oxidation

Question 2

sphingosine 1 phosphate

Answer 2

contributes to cancer and inflammation

-crohns, ulcerative colitis

Question 3

lysosomal storage diseases

Answer 3

-can not break down sphingolipids due to genetic disorders of metabolism

Question 4

different scaffolds

Answer 4

• glycerol

- sphingosine

Question 5

glycerophospholipids

Answer 5

• 2 FAs in ester linkages as positions 1 and 2

- head group in a phosphodiester linkage at position 3

Question 6

head groups

Answer 6

• serine
• choline
• ethanolamine
• glycerol
• inositol

Question 7

cardiolipin

Answer 7

• double phospholipid

- exclusive to the inner membrane of the mitochondria

Question 8

what do fatt acid salts form

Answer 8

• micelles

- individual units are wedge shpaed with a carboxylic head and an aliphatic tail

Question 9

phospholipids form

Answer 9

• membrane bilayers
• individual units are cylindrical
• glycerophospholipids will spontaneously form bilayers in awueous solution

Question 10

flip flopping of membrane lipids

Answer 10

• very unlikely to happen spontaneously
• the enzyme flippase is required
• this has implications in membrane properties such as in RBC’s (PC on outer and PE and PS on inner)

Question 11

common lecithin

Answer 11

• 1 stearoyl, 2 oleoyl-phosphatidyl choline
• most abundant human membrane lipid
• unsaturated FA on C2 lowers melting point creating a fluid membrane

Question 12

lung sufractant

Answer 12

• 1,2 palmytoil-phosphatidyl choline
• reduced fluidity important for coating air-water interface, preventing alveolar collapse
• deficiency can lead to respiratory distress syndrome in premature infants

Question 13

what does the formation of glycerophospholipids start with?

Answer 13

PA or DAG

Question 14

general mechanism for head group addition

Answer 14

1. CDP activation of one hydroxyl by adding phosphate via kinase then CTP via cytidyltransferase
2. second hydroxyl displaces CMP to give phosphodiester

Question 15

starting reactants to make ethanolamine or choline

Answer 15

-start with a head group activated with CDP then add diacylglycerol

Question 16

starting reactants for making inositol (PI), glycerol, or PGC3 (cardiolipin)

Answer 16

-start with diacylglycerol activated with CDP then add a head group

Question 17

glycerophospholipid interconversion

Answer 17

• SAM (S-adenosyl methionine) is used as a methyl donor in several processes
• only way to form PS is to convert it from PE

Question 18

plasmalogens

Answer 18

• glycerophospholipids with fatty alcohol in ether linkage at C1
• activated platelet secretion and alters membrane permeability
• abundant plasmalogens in mitochondrial inner membrane may resist oxidative damage that would hydrolyze the ester bonds in normal PL’s

Question 19

phospholipases

Answer 19

• PLA2 release PUFAs acted upon by oxygenases to make intracellular signaling molecules
• PLAs rearrange FA’s
• PLA’s are found in many venoms

Question 20

modified FA’s as intracellular signals

Answer 20

• certain stresses induce phospholipase A to release long chin PUFAs from membrane phopholipids
• eicosanoids

Question 21

cyclooxygenase

phospholipase

Answer 21

• gives rise to prostaglandins and thromboxanes which act as short range intracellular signals
• removes 2 double bonds, subscript shows number remaining

Question 22

lipoxygenases (phospholipase)

Answer 22

• generate leukotrienes
• important for the immune response
• number of double bonds is unchanged
• modulate cellular chemotaxis, cytokine release
• mediate vascular permeability and bronchioconstriction

Question 23

DAG

Answer 23

• second messenger

- activates PKC

Question 24

IP3

Answer 24

• causes release of Ca2+
• activates calmodulin kinase
• promotes growth and development

Question 25

what are DAG and IP3 released from

Answer 25

- PIP | - extracellular signal binds membrane spanning receptor to activate PLC which cleaves PIP into IP3 and DAG

Question 26

sphingolipids

Answer 26

- membrane lipids not based on glycerol - based on sphingosine - common membrane component in myelin sheath, sphingolyelin with C24 FA's provides electrical insulation

Question 27

multiple myeloma

Answer 27

-auto immune disease where you lose myelination in the CNS

Question 28

types of glycolipid, what is theur classification

Answer 28

- sulfatides - globosides - gangliosides (charged, neuraminic acid) - these are a type of sphingolipid - glucose added as UDP glucose or UDP galactose

Question 29

blood grouping antigens

Answer 29

- these are gangliosides and globosides | - they are markers in cellular recognition

Question 30

normal sphingolipid breakdown pathways

Answer 30

- membrane lipids are constantly pulled from the surface into endosomes - some are reused others are broken down in lysosomes and their components recylcled - each sugar linkage in the glycosphingolipids (cerebrosides, globosides, and gangliosides) requires a seperate enzyems for removal