ch. 5 phospholipids: the membrane's foundation

Question 1

although there are over 1000 distinct lipids identifies in cells, we can organize into only three classes:

Answer 1

1. glycerol phospholipids
2. sphingolipids
3. sterols (such as cholesterol)

Question 2

the classical phospholipid bilayer consists of a combination of glycerol __________ and _____________.

Answer 2

phospholipids, sphingolipids

Question 3

phospholipids form

Answer 3

bilayers because of their amphipathic structure.

Question 4

the polar head groups are ____________, whereas the non polar hydrocarbon tails are _________.

Answer 4

hydrophilic, hydrophobic

Question 5

what happens when a collection of phospholipid molecules is placed in water?

Answer 5

-the polar water molecules repel the long, non polar tails of the phospholipids while seeking partners for hydrogen bonding.
-the non polar tails of the phospholipids end up packed closely together, far away from water. (polar head towards, tails away).

Question 6

a lipid bilayer is stable because

Answer 6

water’s affinity for hydrogen bonding never stops.

Question 7

the degree of membrane fluidity changes with the composition of

Answer 7

the mebrane itself.

Question 8

glycerol phospholipids that are _________ tend to make the membrane less fluid, as they pack well. Similarly, the sphingolipids which are usually _______, also make the membrane less fluid.

Answer 8

saturated, saturated

Question 9

at colder temperatures, the double bonds introduced by fatty acid desaturase make the membrane more _____, counteracting the environmental effect of reduced temperature.

Answer 9

fluid

Question 10

the plasma membrane vs ER membrane

Answer 10

thicker and less permeable, forms tubes and sheets and is more dynamic