18 Lipids and membranes

Question 1

what are the two basic components which make up biological membranes?

Answer 1

it’s made up of lipids and proteins:phospholipids

(glycerophospholipids and sphingomyelin), cholesterol and integral or peripheral proteins

Question 2

what is the amphipathic nature of phospholipids?

Answer 2

(polar) head groups, and (non-polar) hydrophobic fatty acid tails or alipathic tails

Question 3

how are carbohydrates present in biological membranes?

Answer 3

found as glycolipids or glycoproteins on the extracellular side of the membrane

Question 4

the structure of glycolipids

Answer 4

a sphingosine backbone with one to many sugars attached to the lipid

Question 5

what’s a micelle and how does it function?

Answer 5

an amphipathic compound made up of lipid bilayer that interacts with aqueous systems and forms spheres, with an entire hydrophobic core
Involved in intestinal digestion and absorption of lipids

Question 6

what’s a liposome and how does it function?

Answer 6

form spherical vesicles separating the external env’t from an internal aqueous compartment
Involved as carriers of non-permeable solutes

Question 7

types of movement of phospholipids

Answer 7

rapid lateral diffusion (side to side movement), rapid rotational diffusion (spinning in place) and rapid flexing of hydrocarbon chains

Question 8

secondary structures found in transmembrane segments of integral membrane proteins

Answer 8

alpha-helices and B-barrels

Question 9

definition of lipid anchors

Answer 9

lipid anchors have covalently linked lipid inserted into the lipid membrane and attached to peripheral protein.

Question 10

GPI anchor

Answer 10

phosphatidylinositol (in the membrane) attached to covalently linked sugar residues and covalently bound to the carboy terminus of a peripheral protein

Question 11

Fatty acid linked anchor

Answer 11

fatty acid linked to the amino terminus of a peripheral protein

Question 12

isoprenoid lipid anchor

Answer 12

isoprenoid lipid attached to a sulfur group and a peripheral protein

Question 13

factors affecting membrane fluidity

Answer 13

temperature and degree of unsaturation of fatty acid chains

Question 14

temperature and membrane fluidity

Answer 14

increasing Temperature (heating up the lipids) leads to greater membrane fluidity

Question 15

degree of unsaturation of FAs and membrane fluidity

Answer 15

the more unsaturated the Fatty acid, the more kinks from double bonds, and poor packing leads to greater membrane fluidity

Question 16

cholesterol’s effect on membrane fluidity

Answer 16

overall, net lowering in membrane fluidity, cholesterol lowers membrane fluidity due to is structure, rigid plank of four fused rings, limits rotational ability of the fatty acid tails. cholesterol can also increase membrane fluidty in the hydrophobic core of the lipid bilayer since cholesterol does not extend into this region

Question 17

role of lipid rafts

Answer 17

segregate and concentrate or exclude certain proteins to facilitate their activity

Question 18

lipid rafts are…

Answer 18

organized bilayer structure with particular lipids and proteins present, and distinct from the surrounding bilayer. lots of cholesterol and tend to have longer fatty acid chains

Question 19

outer leaflet of lipid rafts contain

Answer 19

glycosphingolipids and cholesterol

Question 20

inner leaflet of lipid rafts contain

Answer 20

sphingomyelins and cholesterol

Question 21

forces which drive the formation of lipid bilyers

Answer 21

hydrophobic forces- hydrophobic, fatty acid tails tend to come together and van der Waals forces