introduction to lipids

Question 1

biological organisms store energy in…

Answer 1

fats/oils

Question 2

what is the role of lipds?

Answer 2

cofactors electron carriers, light absorbing pigments, chaperones, emulsifying agents, hormones, intracellular messengers

Question 3

fatty acids

Answer 3

water-insoluble hydrocarbons used for cellular energy storage; highly reduced and thus provide rich source of stored chemical energy for cells; storage of hydrophobic fats as triacylglycerols is also highly efficient because water is not needed to hydrate the stored fats

Question 4

nomenclature for unbranced fatty acids

Answer 4

chain length and number of bonds separated by a colon; numbering begins at the carboxyl carbon; positions of double bonds indicated by delta and a superscript number

Question 5

polyunsaturated fatty acids (PUFAs)

Answer 5

contain more than one double bond in their backbone: omega-3 fatty acids have double bond between C-3 and C-4 relative to the most distant carbon (w) ; omega-6 fatty acids have double bond between C-6 and C-7 relative to w

Question 6

triacylglycerols

Answer 6

simplest lipids constructed from fatty acid; composed of three fatty acids, each in ester linkage with a single glycerol; can be simple (one kind of fatty acid) or mixed (two or three fatty acids); nonpolar & hydrophobic

Question 7

vertebrates store triacylglycerols as …

Answer 7

lipid droplets in adipocytes (fat cells)

Question 8

plants store triacylglycerols in…

Answer 8

seeds

Question 9

lipases

Answer 9

enzymes that catalyze the hydrolysis of stored triacylglycerols, releasing fatty acids for export to sites where they are required as fuel

Question 10

what contains lipases?

Answer 10

adipocytes and germinating seeds

Question 11

membrane lipids are composed of…

Answer 11

hydrophobic tails attached to polar head groups

Question 12

cellular membranes are composed of a variety of lipids, including glycerophospholipids and sterols. These lipids are used for…

Answer 12

structuring membranes as well as for displaying molecules on the membrane surfaces for signaling and molecular recognition

Question 13

biological membranes

Answer 13

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

Question 14

amphipathic

Answer 14

one end of the molecule is hydrophobic, the other hydrophilic

Question 15

3 types of membrane lipids

Answer 15

phospholipids, glycolipids, sterols

Question 16

phospholipids

Answer 16

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

Question 17

glycolipids

Answer 17

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

Question 18

sterols

Answer 18

compounds characterized by a rigid system of four fused hydrocarbon rings

Question 19

glycerophospholipids (phosphoglycerides)

Answer 19

membrane 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 20

glycerophospholipids head groups

Answer 20

a phosphodiester bond joins the head group of glycerol; phosphate group can bear a negative, neutral, or positive charge

Question 21

ether-linked fatty acids

Answer 21

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 C-1 & C-2 as in plasmalogens

Question 22

sphingolipids

Answer 22

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

Question 23

glycosphingolipids

Answer 23

have head groups with 1+ sugars connected directly to the -OH at C-1 of the ceramide moiety-> do not contain phosphate, occur largely in the outer face of plasma membranes

Question 24

cerebrosides

Answer 24

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 25

globosides

Answer 25

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

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

sterols

Answer 27

structural lipids present in the membranes of most eukaryotic cells; steroid nucleus= consists of four fused rings, almost planar, relatively rigid; cholesterol= major sterol in animal tissues-> amphipathic, polar head group, nonpolar hydrocarbon body, membrane constituents, similar to stigmasterol in plants & ergosterol in fungi

Question 28

steroids

Answer 28

oxidized derivatives of sterols-> lack the alkyl chain attached to ring D of cholesterol, more polar than cholesterol; steroid hormones move through the bloodstream (on protein carriers) to target tissues; binding to highly specific receptor proteins in the nucleus triggers changes in gene expression

Question 29

what regulates cell structure and metabolism?

Answer 29

phosphatidylinositol and its phosphorylated derivates

Question 30

eicosanoids

Answer 30

paracrine hormones, substances that act only on cells near the point of hormone synthesis instead of being transported in the blood
involved in reproductive function, inflammation, fever, & pain associated with injury or disease, formation of blood clots, regulation of blood pressure, gastric acid secretion

Question 31

four major classes of eicosanoids

Answer 31

prostaglandins, thromboxanes, leukotrienes, & lipoxins

Question 32

what leads to accumulation of gangliosides in the cell?

Answer 32

genetic defects in any of these hydrolytic enzymes