making lipids

Question 1

what are lipids?

Answer 1

heterogeneous structure group that are hydrophobic and make up membranes and store energy

Question 2

what type of cells make membranes?

Answer 2

all of them but some more than others

Question 3

what is TAG?

Answer 3

triactlglycerol

Question 4

how is TAG made?

Answer 4

from monoacylglycerols using acyltransferases

Question 5

what are actyltransferases?

Answer 5

enzymes that move fatty acids

Question 6

what is the fatty acid donor?

Answer 6

acyl-CoA

Question 7

what is another way cells can make TAG?

Answer 7

from glycerol-3-phosphate

Question 8

where is TAG made?

Answer 8

in the smooth ER

Question 9

what is the smooth ER?

Answer 9

ER without associated ribisomes

Question 10

where does TAG accumulate?

Answer 10

in organelles called lipid droplets

Question 11

what are lipid droplets?

Answer 11

storage organelles with a single layer membrane that originate at the ER

Question 12

what are perilipins?

Answer 12

a family of proteins that coat lipid droplets (associated with the LD membrane at the cytoplasmic side)

Question 13

what cells dont have TAG synthesis or lipid droplets?

Answer 13

yeast cells

Question 14

what are the steps of making a lipid droplet?

Answer 14

• TAG synthesis and lens formation
• emergence and nascent lipid droplet formation
• lipid droplet budding and growth

Question 15

where does triacylglycerol synthesis occur?

Answer 15

at smooth ER bilayer

Question 16

what is the first step of triacylglycerol synthesis?

Answer 16

TAG synthesis and cholesterol ester synthesis enzymes deposit neutral lipids in between the leaflets of ER bilayer

Question 17

what is the second step of triacylglycerol synthesis?

Answer 17

seipin and other lipid droplet biogenesis factors are recruited to lens structure and facilitate the growth of nascent lipid droplet

Question 18

which direction does budding happen?

Answer 18

towards the cytoplasmic side

Question 19

what forces contribute to budding?

Answer 19

• assymetry in phosphlipid compostion
• seipin push from ER side
• asymmetry in protein recruitment from the cytosol side

Question 20

what is the third step of TAG synthesis?

Answer 20

lipid droplets bud from the Er and grow through fusion of local lipid synthesis

Question 21

what role does phosphatidic acid play in TAG?

Answer 21

can make TAG (remove phosphate) or become phospholipids,

Question 22

where are enzymes that metabolize phospholipids never found?

Answer 22

in the cytosol