L4 - lipids and membranes Flashcards
give example of how glycerophospholipids are named
phosphatidyl — name of polar head group
(FA, P, G)
phosphatidyl - choline
phosphatidylcholine
what two structures can phospholipids be based on?
TAG
sphingosine
where is sphingomyelin found
myelin sheaths of neurons
describe sphingosine structure
glycerol backbone the same as a TG
has 1x FA
has 1x NH3+
has 1x OH
bound to the 3 C’s
how is a phospholipid made from sphingomyelin?
add FA chain to the NH3+ group
add a phosphate and polar head group to OH
what structure are glycolipids based on?
sphingosine
example of a glycolipid?
cerebrosides
what are cerebrosides
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
what are gangliosides
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
why are glycolipids common in signalling?
the oligosaccharide on sphingosine forms 3D structure that can be recognised
describe palmic acid
most common FA in plants and animals
saturated
describe stearic acid
waxy
saturated
describe oleic acid
mono unsaturated
are naturally occurring FAs usually found in cis or trans configuration
cis
highest priority sae side
what is important about linoleic and linoleic acid
essential in diet - cant be synthesised
required in membranes
properties of membranes
- flexible
- fluid
-lipids diffuse sideways
-lipids can ‘flip - flop’ from one side of membrane to
other aided by flippase enzymes
describe Gel membrane structure
lipids tightly packed
thicker membrane
describe liquid crystal membrane
loosely packed lipids
disordered tails
thinner membrane
the state the membrane must stay in
describe transition from gel to liquid crystal membrane
heat
gel<=======> liquid crystal
effect of longer chain FAs in the membrane fluidity
increase transition temperature to liquid cyrstal
decrease membrane fluidity
effect of unsaturated FAs on membrane fluidity
increase fluidity
cant be tightly packed
how do bacteria regulate fluidity of membrane in response to temp?
change proportion of unsaturated FAs in membrane
what effect does cholesterol have on the membrane at high temps
stiffens membrane by filling space between FAs so membrane isnt too fluid
what effect does cholesterol have on the membrane at low temps
prevents FA tails packing too closely which increases fluidity
what properties of cholesterol allow it to regulate membrane fluidity?
hphilic head
hphobic tail
