lipids and membranes Flashcards
what are non-essential fatty acids?
synthesised by your body
give examples of non-essential fatty acids
oleic acid
palmitic acid
stearic acid
what are essential fatty acids?
fatty acids that must be obtained from the diet
give examples of essential fatty acids
omega 6 (linoleic acid) omega 3 (alpha linoleic acid)
where can you get linoleic acid from?
sunflower or olive oil
where can you get alpha linoleic acid from?
seeds and nuts
which end of the fatty acid is the omega end?
methyl end
what is another name for omega-9?
oleic acid
why is oleic acid considered a non-essential fatty acid?
we have the desaturase enzyme to induce the double bond at carbon 9
why are fatty acids an efficient store of energy?
1g fatty acid = 6g of glycogen
how are triglycerides stored?
fat droplets
monolayer
how are triglycerides used when energy is needed by the body?
hydrolysis splits it into glycerol and three fatty acids
FAs bind to albumin
carry it to the muscles which then use it for energy
whats a sphingolipid?
like a triglyceride, but a serine instead of glycerol and two fatty acids instead of one
what is the structure of a glycolipid?
two long hydrocarbon chains attached to one or more sugars
what do glycolipids do?
surface of all plasma membranes
needed in cell to cell contact
protects cell from a hostile environment
what’s the difference between glycerophospholipids and sphingolipids?
spingolipids are more saturated - straighter and pack more tightly together
what happens when you add cholesterol to glycerophospholipids?
makes the membrane less fluid
what happens when you add cholesterol to sphingolipids?
makes the membrane more fluid
what are lipid rafts?
when sphingolipids and cholesterol self-associate to creat lipid rafts which membrane proteins can dock
do glycerophospholipids tend to be on the inside or outside of the membrane and why?
inside because they’re negative
do sphingolipids tend to be on the inside or outside of the membrane?
outside
what is cholesterol a precursor to?
bile salts
vitamin D
steroids
sex hormones
where is cholesterol converted to bile?
in the liver
how is cholesterol carried around the blood?
lipoproteins
what causes atherosclerosis?
high levels of LDL
what is omega 6 a precursor to?
arachidonic acid
what is omega 3 a precursor to?
EPA
what is COX-2?
an enzyme necessary for conversion of arachidonic acid to prostaglandins
what can arachidonic acid and EPA make?
paracrines
leukotriences
prostaglandins
thromboxanes
what does amphillic mean?
water hating and water loving
what are the zones of a bilayer?
two hydrophillic regions with a hydrophobic region int he middle
how are fatty acyl chains made?
ketosynthase - joins 2 carbon compounds together and removes CO2
reduction reactions via ketoreductase, dehydratase and enoylreductase
thioesterase forms fatty acid
what does saturated mean?
no double bonds
what does unsaturated mean?
double bonds
what is oleic acid?
18C compound
monounsaturated
omega 9
whats the difference between cis and trans oleic acid?
cis = kinked trans = straight, made in industry for food
what is oleic acid made from?
stearic acid using desaturase
what is linoleic acid?
omega 6 polyunsaturated
what is alpha linoleic acid?
omega 3 fatty acid
what are paracrines?
short-lived, near-acting, cyclic FA signalling molecules
mediators of inflammation, pain, fever, immunosuppression, clotting, blood vessel constriction etc
name paracrines and where they’re made?
o Leukotrienes – made by leukocytes
o Prostaglandins – made in all tissues
o Thromboxanes – made by platelets
explain how paracrines are made?
phospholipase converts membrane lipids to O3/6
O3 –> EPA
O6 –> arachidonic acid
by elongases and desaturases
COx2 then converts these to paracrines
what drugs target COX2?
NSAIDs like aspirin, ibuprofen and indomethicin
why is omega 9 non-essential fatty acid?
we have the desaturase enzyme to break this down
how are fatty acids stored?
triglycerides
describe the structure of triglycerides?
one molecule of glycerol with 3 fatty acids attached to it
how are triglycerides used for energy?
- Triglyceride split into Glycerol and Fatty acids via hydrolysis
- FAs bind to Albumin which transports the FAs to muscle cells
- Muscle cell takes up the FAs and uses it for energy
what are the 3 main membrane lipids?
- Glycerophospholipids
- Sphingolipids (includes glycolipids)
- Cholesterol
describe the structure of glycerophospholipids
glycerol linker attaches to 2 fatty acids - one is straight and one is kinked
3rd attachment is a phosphate group with a choline head
describe the structure of sphingolipids
- Serine “linker”
- Attaches to 2 Fatty acid tails (non polar)
- 3rd attachment can be to any functional group (polar)
what are glycolipids and what do they do?
type of sphingolipid
protect cell from hostile environment
what’s the difference between glycerophospholipids and sphingolipids?
glycero - more double bonds so its shorter and more kinked
sphingo - fully saturated
what does adding cholesterol do to glycerophospholipids?
makes it more densely packed, less fluid and less permeable
what does adding cholesterol to sphingolipids do?
more fluid bc it pushes them apart
how are lipid rafts made?
• Sphingolipid and cholesterol self-associate to create fluid lipid rafts into which different functional membrane proteins can “dock.”
why do membrane lipids make a bilayer?
membrane lipids are cylinders. In water, they maximise the packing by forming a sheet that is also a bilayer. Acyl chains interact with each other and the head groups interact with the water
why do fatty acids make micelles?
Fatty acids are conical. When they’re in water, they self-associate because the hydrocarbon tail is hydrophobic and the carboxyl head is hydrophilic
what is a liposome?
membrane lipid ball with no other molecules
how are liposomes used?
used to study behaviour of lipid membranes (and, because they are readily taken up by cells, have also been used to deliver drugs and DNA to patients)
what does fluidity of the membrane refer to?
- Acyl chains can flex
- Rotation of membrane lipids in the bilayer
- Diffuse laterally within the leaflet
- ”Flip Flop” (rare) – involves hydrophilic head moving through hydrophobic tails
what does mosaicity refer to?
how many membrane proteins are embedded in the bilayer
