Module 8: Lipids

Question 1

are lipids soluble in water

Answer 1

no, they are a diverse family of compounds sharing a defining feature of insolubility of water

Question 2

2 ways that lipids differ from other biomolecules

Answer 2

tend to be of lower molecular weight
-form aggregates rather than polymers

Question 3

biological functions of lipids

Answer 3

-energy storage
-structural components of membranes
-signaling
-enzyme co-factors and vitamins

Question 4

Fatty acids

Answer 4

hydrocarbon with carboxylic head
-differ in length and degree of saturation
-usually even number of carbons 12-24

Question 5

double bonds within fatty acids

Answer 5

saturated- no double bonds
unsaturated- 1 double bond
polyunsaturated- multiple double bonds
double bonds usually cis configuration
double bonds usually separated by methylene group

Question 6

nomenclature of fatty acids

Answer 6

carbons: # double bonds, double bond position

Question 7

where is carbon 1 on fatty acids

Answer 7

the carbon of the carboxyl group

Question 8

fatty acid structure

Answer 8

hydrocarbon tails of fatty acids associate through hydrophobic and van der Walls interactions
-long chains have stronger associations than short chains
-saturated chains have stronger association than unsaturated

Question 9

what does the melting temperature of fatty acids reflect

Answer 9

the length and degree of saturation of the hydrocarbon tails
-double bonds have a greater influence than the length of the tail on fatty acid association

Question 10

fats and oils as energy storage molecule

Answer 10

lipids represent critical energy storage for plants and animals
-lipids occupy most of the intracellular space adipocytes, the energy storage cells in animal tissue
-storage of fat under the skin also provides insulating function

Question 11

how are fatty acids required for energy stored

Answer 11

triacylglycerols

Question 12

tricylglycerols

Answer 12

three fatty acids linked to glycerol through ester linkages

Question 13

difference between simple and complex tricylglycerols

Answer 13

simple: have the same three fatty acids at each position
complex: different fatty acids

Question 14

how are triacylglycerols made more hydrophobic

Answer 14

ester linkage remove the polar carboxyl group

Question 15

how much more energy is in fats compared to carbohydrates

Answer 15

on a gram per gram basis there is 6 times as much energy in fat
-fat represents the key molecule for long term energy storage

Question 16

what are the characteristics of lipids that make them so effective as long term energy storage molecule

Answer 16

low oxidation state: less oxygenated fuels burn more efficiently’ triacylglycerols have lower oxygenation state than carbohydrate
high hydration state: lipids are hydrophobic with limited interaction with water providing a compact, dehydrated energy storage form

Question 17

saponification

Answer 17

treatment of fat with a strong base breaks the ester linkages to release free fatty acids to make soap

Question 18

what makes free fatty acids effective in solubilization of hydrophobic substances

Answer 18

the amphipathic properties

Question 19

how do fatty acids function as detergents and soaps

Answer 19

through formation of micelles that capture hydrophobic molecules

Question 20

waxes

Answer 20

esters of long chain fatty acids and long chain alcohols
-very water insoluble and high melting point
-widely distributed in nature as waterproof coatings

Question 21

how do membranes form

Answer 21

spontaneously as consequence of the properties of the molecules that compose them

Question 22

how can membrane lipids be classified

Answer 22

based on their backbone ( glycerol vs sphingosine)
or by their polar head group ( phospho vs glyco)

Question 23

what are the similar overall shapes and properties of membrane lipids

Answer 23

two hydrophobic tails
hydrophilic head group

Question 24

glycerophospholipids

Answer 24

most abundant lipid in membranes
-glycerol backbone with phosphate at the C3 position
-the phosphate group is the point of attachment for a variety of polar head groups

Question 25

glycerol-3-phosphate + 2 fatty acids =

Answer 25

phosphatidate

Question 26

glycerophospholipids

Answer 26

glycerophospholipids have a variety of polar head groups -head groups can carry positive, negative or neutral charge -different head groups are likely associated with specialized functions

Question 27

how do plants use phosphate

Answer 27

phosphate availability is often limiting in plants -to conserve phosphate for more critical applications some plants use sugar and sulfate polar head groups

Question 28

galactolipids

Answer 28

in plants one or two galactose groups linked to C3 of diacylglycerol plants also contain sulfolipids

Question 29

sphingolipids

Answer 29

derived from sphingosine

Question 30

sphingosine

Answer 30

structurally similar to monoacyl glycerol -single fatty acid linked by amide bond to form ceramide -ceramide is structurally similar to diacylglycerol

Question 31

how are sphingolipids similar to glycerophospholipids

Answer 31

a variety of polar head groups can be attached to ceramide

Question 32

common sphingolipids

Answer 32

sphingomyelins -phosphocholine cerebrosides -glycosphingolipid -single sugar unit gangliosides -glycosphingolipid -multiple sugar units

Question 33

how do glycosphingolipids determine blood type

Answer 33

cells recognize as self or non-self based on patterns of surface exposed to carbohydrates -transfusion of incompatible blood type causes severe immunological reaction -different blood types reflect different sugar patterns as the head groups of sphingolipids

Question 34

what do membrane lipids of extremophiles contain

Answer 34

ether linkages branch points within hydrocarbon tails membrane spanning hydrocarbon tails composed from a single molecule

Question 35

sterols

Answer 35

structural membrane lipids -serve as precursors for many biologically active products

Question 36

structure of sterols

Answer 36

four fused ring steroid nucleus: 3 six carbon rings and a 5 carbon D ring ring system is rigid and nearly planar

Question 37

cholesterol

Answer 37

serves several critical biological functions such as mediating membrane fluidity and serving as a precursor of steroid hormones and bile salts

Question 38

active roles of lipids

Answer 38

intracellular signaling molecules hormones enzyme cofactors pigments vitamins

Question 39

phosphatidylinsitols

Answer 39

act as intracellular signal -on the inner membrane surface -activation of phospholipase C in response to an extracellular signal triggers the cleavage of head group to produce inositol 1,4,5 triphosphate which increase Ca

Question 40

what do Ca and diacylglycerol activate

Answer 40

specific intracellular pathways/processes

Question 41

eicosanoids

Answer 41

paracrine hormones derivative of C20 polyunsaturated fatty acids

Question 42

three classes of eicosanoids

Answer 42

prostaglandins -constriction of blood vessels thromboxane -blood clot formation leukotriene -smooth muscle contraction

Question 43

steroid hormones

Answer 43

hydrophobic oxidized sterol derivatives -carried through blood stream by carrier proteins -pass through plasma membrane to bind receptors in the nucleus -alter patterns of gene expression and metabolism

Question 44

what are the 4 lipid vitamins

Answer 44

K, A, D, E

Question 45

feature of lipid vitamins

Answer 45

contain rings and long, aliphatic side chains highly hydrophobic

Question 46

Vitamin D

Answer 46

regulates calcium uptake and deposition can be obtained from diet or produced endogenously

Question 47

endogenous production of vitamin D

Answer 47

occurs in a series of reaction, one of which requires UV light

Question 48

vitamin D deficiency

Answer 48

rickets skeletal defects

Question 49

excessive vitamin D

Answer 49

calcification of soft tissues

Question 50

Vitamin A

Answer 50

obtained in liver, egg yolks, and milk -some animals have sufficient A in their livers to present a danger to humans if they are consumed

Question 51

three forms of vitamin A

Answer 51

alcohol (retinol), aldehyde, and retinoic acid

Question 52

why is retinal (aldehyde) important

Answer 52

light sensitive compound with a role in vision

Question 53

Vitamin E

Answer 53

reducing reagent that scavenges oxygen free radicals -may prevent damage to fatty acids in membranes -often used as an additive in cosmetics

Question 54

vitamin E deficiency

Answer 54

scaly skin, muscular weakness and sterility

Question 55

Vitamin K

Answer 55

required for synthesis of blood coagulation proteins

Question 56

how is vitamin K used

Answer 56

in 1920s warfarin was used to cause excessive bleeding in rats -vitamin K analogs like warfarin are now given to individuals who suffer excessive blood clotting

Question 57

which lipid molecule has two hydrocarbon tails and a polar head group

Answer 57

sphingomyelin

Question 58

what vitamin is involved in blood coagulation

Answer 58

K

Question 59

give an example of a saturated fatty acid

Answer 59

18:0

Question 60

give an example of a fatty acid likely to exist as a liquid

Answer 60

18:3, > 8,11,14

Question 61

which class of lipid molecule is least likely to be found within the membrane

Answer 61

triacylglycerols

Question 62

give an example of a fatty acid likely to be solid at room temperature

Answer 62

22:0

Question 63

aspirin blocks the formation of which eicosanoid

Answer 63

prostaglandin and thromboxane

Question 64

true or false sphingolipids contain two fatty acids linked to sphingosine by ester bonds

Answer 64

false

Question 65

true or false some sphingolipids are glycolipids

Answer 65

true

Question 66

true or false ceramide is a parent compound of sphingolipids

Answer 66

true

Question 67

true or false sphingosine is an amino alcohol

Answer 67

true

Question 68

true or false some sphingolipids are phospholipids

Answer 68

true