L4 - lipids and membranes

Question 1

give example of how glycerophospholipids are named

Answer 1

phosphatidyl — name of polar head group
(FA, P, G)

phosphatidyl - choline
phosphatidylcholine

Question 2

what two structures can phospholipids be based on?

Answer 2

TAG

sphingosine

Question 3

where is sphingomyelin found

Answer 3

myelin sheaths of neurons

Question 4

describe sphingosine structure

Answer 4

glycerol backbone the same as a TG

has 1x FA
has 1x NH3+
has 1x OH

bound to the 3 C’s

Question 5

how is a phospholipid made from sphingomyelin?

Answer 5

add FA chain to the NH3+ group

add a phosphate and polar head group to OH

Question 6

what structure are glycolipids based on?

Answer 6

sphingosine

Question 7

example of a glycolipid?

Answer 7

cerebrosides

Question 8

what are cerebrosides

Answer 8

the same as sphingosine phospholipid, only the phosphate and polar head group are replaced by single sugar head group (eg glucose)

glycerol backbone
1x FA
1 x FA on NH3+ group
1 x sugar group on OH group C

Question 9

what are gangliosides

Answer 9

the same as phospholipid based on sphingosine, only the phosphate and polar head group replaced with oligosaccharide

glycerol backbone
1x FA
1 x FA on NH3+ group
1 x olligosaccharide on OH group C

Question 10

why are glycolipids common in signalling?

Answer 10

the oligosaccharide on sphingosine forms 3D structure that can be recognised

Question 11

describe palmic acid

Answer 11

most common FA in plants and animals

saturated

Question 12

describe stearic acid

Answer 12

waxy

saturated

Question 13

describe oleic acid

Answer 13

mono unsaturated

Question 14

are naturally occurring FAs usually found in cis or trans configuration

Answer 14

cis

highest priority sae side

Question 15

what is important about linoleic and linoleic acid

Answer 15

essential in diet - cant be synthesised

required in membranes

Question 16

properties of membranes

Answer 16

1. flexible
2. fluid
   -lipids diffuse sideways
   -lipids can ‘flip - flop’ from one side of membrane to
   other aided by flippase enzymes

Question 17

describe Gel membrane structure

Answer 17

lipids tightly packed

thicker membrane

Question 18

describe liquid crystal membrane

Answer 18

loosely packed lipids
disordered tails
thinner membrane

the state the membrane must stay in

Question 19

describe transition from gel to liquid crystal membrane

Answer 19

heat

gel<=======> liquid crystal

Question 20

effect of longer chain FAs in the membrane fluidity

Answer 20

increase transition temperature to liquid cyrstal

decrease membrane fluidity

Question 21

effect of unsaturated FAs on membrane fluidity

Answer 21

increase fluidity

cant be tightly packed

Question 22

how do bacteria regulate fluidity of membrane in response to temp?

Answer 22

change proportion of unsaturated FAs in membrane

Question 23

what effect does cholesterol have on the membrane at high temps

Answer 23

stiffens membrane by filling space between FAs so membrane isnt too fluid

Question 24

what effect does cholesterol have on the membrane at low temps

Answer 24

prevents FA tails packing too closely which increases fluidity

Question 25

what properties of cholesterol allow it to regulate membrane fluidity?

Answer 25

hphilic head

hphobic tail