Lipids and membranes

Question 1

why are lipids insoluble?

Answer 1

because they are very heterogenous and hydrophobic

Question 2

because lipids are insoluble what is a challenge?

Answer 2

transport and storage

Question 3

what do lipids associate into?

Answer 3

bilayer, micelles, vesicles, droplets, and complex with proteins; they are rarely free in solution

Question 4

what are the different classifications of lipids based on structure (5)

Answer 4

fatty acids, tricylglycerols, phospholipids, isoprenoids/steroids, glycolipids

Question 5

what are fatty acids?

Answer 5

aliphatic carboxylic acids

Question 6

what are tricylglycerols

Answer 6

3 fatty acids esterified to a glycerol

Question 7

what are phospholipids?

Answer 7

phospho head groups attached to a diacylglycerol

Question 8

what are steroids?

Answer 8

cholesterol

Question 9

what are glycolipids?

Answer 9

a phospholipid that has a mono or disaccharide attached as a head group

Question 10

what are the different classifications based on function?

Answer 10

cellular structures (membrane bilayers, vesicles), energy storage (trcylglycerols=fat), bioactivity (vitamins, hormones, 2ndary messengers)

Question 11

what makes fatty acids amphipathic?

Answer 11

the carboxyl groups is hydrophilic and the the hydrocarbon tail is hydrophobic

Question 12

What are the two types of fatty acids?

Answer 12

saturated (no double bonds) or unsaturated (double bonds)

Question 13

what do most natural unsaturated FAs have?

Answer 13

unconjugated cis double bonds

Question 14

how are most FAs found in the body?

Answer 14

esterified to cholesterol or glycerol or bound to an albumin

Question 15

what are some FA derivatives?

Answer 15

soaps– are the Na+ salts of FAs
waxes are FAs esterified to long chain alcohols
prostoglandins, thromboxanes, leukotrienes

Question 16

where are tricylglycerols found?

Answer 16

circulating lipoproteins or in insoluble cytosolic lipid droplets

Question 17

how are TAGs in lipoproteins delivered in the blood to peripheral tissues?

Answer 17

as a fuel source or for storage in adipose tissue

Question 18

in adipose tissue what can TAG in droplets be hydrolyzed to release?

Answer 18

glycerol and FFA for delivery into tissues or the liver

Question 19

what is the major energy reservoir in the body?

Answer 19

TAGs

Question 20

Glycerophospholipids variability of head groups?

Answer 20

cary by charge, cellular location and effects on membrane curvature and protein function. Gives them different characteristics

Question 21

what do phospholipids primarily compose?

Answer 21

cellular membranes and vesicles

Question 22

what are phospholipids pre-cursors of?

Answer 22

lipid 2ndary messengers

position specific cleavage of PIP2 by phospholipases generates bioactive molecules such as diacylglycerol

Question 23

what are sphingomyelin and glycosphingolipids?

Answer 23

contain a sphingo backbone and have signalling and recognition roles and are abundant in the brain

Question 24

what is specific about glycosphingolipids?

Answer 24

they are synthesized and degraded strictly in ordered pathways: genetic defects in lysosomal GSL degradation causes severe neurodegenerative diseases

Question 25

what does cholesterol play an important role in?

Answer 25

maintaining lipid bilayer fluidity, and is a precursor of bile acids, steroid hormones and vitamin D, it is highly insoluble and must be transported in lipoproteins imbalances in which cause atheroclerosis and vascular diseases

Question 26

what coordinates intercellular transport and regulation of cholesterol?

Answer 26

the liver!

Question 27

is cholesterol excreted or degraded in humans?

Answer 27

excreted

Question 28

what are isoprenoids derived from?

Answer 28

cholesterol intermediates–dolichol and ubq

Question 29

what happens when lipids meet water?

Answer 29

they spontaneously associate due to their amphilic or hydrophobic nature, adopt many different structures dependent on size, shape and charge

Question 30

what are the different structures lipids can form?

Answer 30

Droplets (TAGs)
micelles (FFAs, lyso-PLs)
vesicles (PLs)
bilayers (PLs)
monolayers (air-water interface)

Question 31

what can micelle-forming lipids act as?

Answer 31

detergents (SDS)

Question 32

what type of movement is allowed in lipid bilayers?

Answer 32

lateral diffusion and rotation but not flip floping in order to maintain asymmetry

Question 33

what are integral membrane proteins?

Answer 33

embedded in the layer, interact with hydrophobic tails, you can’t get them out unless u solubilize the membrane

Question 34

what are peripheral proteins?

Answer 34

attached using electrostatic force to outside of membrane

Question 35

how do cis double bonds affect lipid bilayers?

Answer 35

decrease the melting point of crystalline PLs in lipid bilayers because membranes must be fluid at room T

Question 36

what increases membrane fluidity?

Answer 36

the degree of FA unsaturation, length decreases it

Question 37

how does cholesterol influence membrane fluidity?

Answer 37

smooths the transition between solid and liquid PL phases

modulates fluidity

Question 38

what can integral membrane proteins span the bilayer as?

Answer 38

alpha helices (mammals) and beta barrels (bacteria)

Question 39

what do cytoskeletal proteins do?

Answer 39

restrict lateral motion of proteins in vivo

Question 40

what do GPI linkages do?

Answer 40

can very easily make a soluble nonmembrane protein into a membrane protein

Question 41

what are lipid membrane domains?

Answer 41

relatively transient lateral regions within membrane bilayers that have distinct lipid/protein compositions and functions

Question 42

what do lipid rafts tend to be like?

Answer 42

thicker, less fluid, lots of cholesterol, sphingolipids, and fatty acylated proteins