10.2 Structural Lipids in Membranes

Question 1

Biological membrane

Answer 1

double layer of lipids that acts as a barrier to polar molecules and ions

Question 2

membrane lipids are

Answer 2

amphipathic- one end of the molecule is hydrophobic, the other hydrophilic

hydrophobic regions associate with each other
hydrophilic regions associate with water

Question 3

4 General types of Membrane Lipids

Answer 3

phospholipids
glycolipids
archaeal tetraether lipids
sterols

Question 4

phospholipids

Answer 4

have hydrophobic regions composed of 2 fatty acids joined to glycerol or sphingosine

Question 5

glycolipids

Answer 5

contain a simple sugar or a complex oligosaccharide at the polar ends

Question 6

archaeal tetraether lipids

Answer 6

have two very long alkyl chains ether-linked to glycerol at both ends

Question 7

sterols

Answer 7

compounds characterized by a rigid system of four fused hydrocarbon rings

Question 8

glycerophospholipids are derivatives of

Answer 8

phosphatidic acid

Question 9

glycerophospholipids (phosphoglycerides)

Answer 9

membranes lipids in which two fatty acids are attached in ester linkage to the first and second carbons of glycerol, and a highly polar or charged group is attached through a phosphodiester linkage to the third carbon

Question 10

glycerophospholipids are named as derivatives of phosphatidic acid

Answer 10

a phosphodiester bond joins the head group to glycerol

the phosphate group can bear a negative, neutral, or positive charge

phosphatidyl+ head group

Question 11

the fatty acids in glycerophospholipids

Answer 11

can be any of a wide variety
in general, glycerophospholipids contain:
-a C16 or C18 saturated fatty acid at C1
-a C18 or C20 unsaturated fatty acid at C2

Question 12

some glycerophospholipids have ether-linked fatty acids

Answer 12

ether lipids: one of the two acyl chains is attached to glycerol in ether, rather than ester, linkage
-chain may be saturated
-chain may contain a double bond between C1 and C2 as in plasmalogens
-vertebrate heart tissue is uniquely enriched with ether lipids
-functional significance is unknown (they are resistant to some phospholipases)

Question 13

platelet-activating factor

Answer 13

an ETHER lipids that serves as a potent molecular signal

Question 14

platelet-activating factor is released from

Answer 14

leukocytes called basophils

Question 15

platelet-activating factor stimulates

Answer 15

platelet aggregation and serotonin release

plays a role in inflammation and the allergic response

(active lipid- not necessarily a membrane lipid)

Question 16

galactolipids

Answer 16

member of the glycolipids group that predominate in plant cells
-one or two galactose residues are connected by a glycosidic linkage to C3 of a 1,2-diacylglycerol

Question 17

sphingolipids are derivatives of

Answer 17

sphingosine

Question 18

sphingolipids

Answer 18

large class of membrane phospholipids and glycolipids
-have a polar head group and two nonpolar tails
-contain NO glycerol
-contain one molecule of the long-chain amino alcohol sphingosine or one of its derivatives

Question 19

ceramides are the

Answer 19

structural parent of all sphingolipids

C1, C2, and C3 of sphingosine are structurally analogous of the three carbons of glycerol in glyceorphospholipids

Question 20

ceramide

Answer 20

compound resulting when a fatty acid is attached in amide linkage to the -NH2 on C2
-structurally similar to a diacylglycerol

Question 21

sphingomyelins

Answer 21

subclass of sphingolipids that contains phosphocholine or phosophoethanolamine as their polar head group

Question 22

glycosphingolipids

Answer 22

have had groups with 1+ sugars connected directly to the -OH at C1 of the ceramide moiety
-does NOT contain phosphate
-occur largely in the outer face of plasma membranes

Question 23

cerebrosides

Answer 23

have a single sugar linked to ceramide
-those with galactose are found in the plasma membranes of cells in neural tissue
-those with glucose are found in the plasma membranes of cells in nonneural tissues

Question 24

globosides

Answer 24

glycosphingolipids with 2+ sugars, usually D-glucose, D-galactose, or N-acetyl-D-galatosamine

Question 25

sometimes called neutral glycolipids, as they have no net charge at pH 7

Answer 25

cerebrosides
globosides

Question 26

gangliosides

Answer 26

have oligosaccharides as their polar head groups and 1+ residues of N-acetylneuraminic acid (Neu5Ac), a sialic acid, at the termini

Question 27

1 sialic acid residue

Answer 27

GM (M for mono) series

Question 28

2 sialic acid residues

Answer 28

GD (D for di) series

Question 29

3 sialic acid residues

Answer 29

GT (T for tri) series and so on

Question 30

sphingolipids at cell surfaces are sites of biological recognition

Answer 30

-prominent in the plasma membrane of neurons
-human blood groups are determined in part by the oligosaccharide head groups of these glycosphingolipids

Question 31

phospholipids and sphingolipids are degraded in

Answer 31

lysosomes

Question 32

phospholipases of the A type

Answer 32

remove one of the two fatty acids

Question 33

lysophospholipases

Answer 33

remove the remaining fatty acid

Question 34

lysosomal enzymes

Answer 34

catalyze the stepwise removal of sugar units of gangliosides yielding a ceramide

Question 35

abnormal accumulations of membrane lipids

Answer 35

genetic defects in any of these hydrolytic enzymes leads to the accumulation of GANGLIOSIDES in the cell

Question 36

sterols

Answer 36

structural lipids present in the membranes of most eukaryotic cells

have four fused carbon rings

steroid nucleus:
-consists of four fused rings
-almost planar
-relatively rigid

Question 37

cholesterol

Answer 37

major sterol in animal tissues
-amphipathic
-polar head group
-nonpolar hydrocarbon body
-membrane constituents
-similar to stigmasterol in plants and ergosterol in fungi

Question 38

sterols serve as precursors for products with specific biological activities

Answer 38

-steroid hormones regulate gene expression

Question 39

bile acids

Answer 39

polar derivatives of cholesterol that emulsify dietary fats in the intestine to make them more readily accessible to digestive lipases