making lipids Flashcards
what are lipids?
heterogeneous structure group that are hydrophobic and make up membranes and store energy
what type of cells make membranes?
all of them but some more than others
what is TAG?
triactlglycerol
how is TAG made?
from monoacylglycerols using acyltransferases
what are actyltransferases?
enzymes that move fatty acids
what is the fatty acid donor?
acyl-CoA
what is another way cells can make TAG?
from glycerol-3-phosphate
where is TAG made?
in the smooth ER
what is the smooth ER?
ER without associated ribisomes
where does TAG accumulate?
in organelles called lipid droplets
what are lipid droplets?
storage organelles with a single layer membrane that originate at the ER
what are perilipins?
a family of proteins that coat lipid droplets (associated with the LD membrane at the cytoplasmic side)
what cells dont have TAG synthesis or lipid droplets?
yeast cells
what are the steps of making a lipid droplet?
- TAG synthesis and lens formation
- emergence and nascent lipid droplet formation
- lipid droplet budding and growth
where does triacylglycerol synthesis occur?
at smooth ER bilayer
what is the first step of triacylglycerol synthesis?
TAG synthesis and cholesterol ester synthesis enzymes deposit neutral lipids in between the leaflets of ER bilayer
what is the second step of triacylglycerol synthesis?
seipin and other lipid droplet biogenesis factors are recruited to lens structure and facilitate the growth of nascent lipid droplet
which direction does budding happen?
towards the cytoplasmic side
what forces contribute to budding?
- assymetry in phosphlipid compostion
- seipin push from ER side
- asymmetry in protein recruitment from the cytosol side
what is the third step of TAG synthesis?
lipid droplets bud from the Er and grow through fusion of local lipid synthesis
what role does phosphatidic acid play in TAG?
can make TAG (remove phosphate) or become phospholipids,
where are enzymes that metabolize phospholipids never found?
in the cytosol
