Lipids: Biosynthesis of Storage Lipids, Membrane Lipids, and Steroids

phosphatidate

the common precursor derived from glucose that is involved in the synthesis of TAGs and phospholipids in the endoplasmic reticulum

glycerol 3-phosphate

can be derrived from glycerol (from TAG breakdown) or dihydroxyacetone phosphate (from glycolysis)

free fatty acids

phosphatidate can be converted into TAGs with addition of _______________________

alcohol

phosphatidate can be converted into phospholipids with addition of ___________

SAMe (3 S-Adenosyl methionine)

methyl group carrier involved in the conversion of phosphatidylethanolamine into phosphatidylcholine

also a dietary supplement

ceramide

precursor to sphingomyelin and cerebroside; forms their backbone

cerebroside

UDP-glucose converts ceramide into _____________

sphingomyelin

phosphatidylcholine converts ceramide into ________________

cholesterol

three stages of _______________ synthesis:

1) synthesis of isopentenyl pyrophosphate (IPP)

2) condensation of 6 molecules of IPP

3) cyclization of squalene

consumes

the synthesis of isopentenyl pyrophosphate __________ energy

HMG-CoA reductase

key enzyme in cholesterol biosynthesis that converts HMG CoA into mevalonate

liver

main location of cholesterol biosynthesis

mevalonate

what HMG CoA gets converted into - pivotal step in cholesterol synthesis

isoprene

5 carbon building block unit produced in stage 1 of cholesterol biosynthesis

geranyl pyrophosphate

condensation of dimethylallyl pyrophosphate (5C) and isopentenyl pyrophosphate (5C) form _________________ (10C)

farnesyl pyrophosphate

condensation of geranyl pyrophosphate (10C) with another isopentenyl pyrophosphate (5C) forms _________________ (15C)

squalene

tail-to-tail condensation of two farnecyl pyrophosphate form ________________ (30C)

NADPH

the synthesis of squalene consumes ______________

NADPH

the oxidation of squalene to produce a squalene epoxide consumes ______________ to produce water from molecular oxygen

ER (endoplasmic reticulum)

location of the synthesis of squalene and cholesterol

27

number of carbons in cholesterol

chylomicron

the largest lipoprotein that only is formed after eating and digesting fats

VlDL

very low density lipoprotein; loaded with lipids

LDL

low density lipoprotein; major carrier of cholesterol in the blood

HDL

high density lipoprotein; the main scavenger of cholesterol in the blood

insulin

increases the expression of SREBP (sterol regulatory element binding protein), allowing for increased expression of HMG CoA reductase to produce cholesterol

degredation

excess cholesterol binds to a receptor resulting in the ________________ of HMG CoA reductase (feedback inhibition)

active

high levels of AMP dephosphorylates HMG CoA reductase, making it _____________

inactive

high levels of ATP phosphorylates HMG CoA reductase, making it _____________

competitive

statins act through ________________ inhibition of HMG CoA reductase - prevents the formation of mevalonic acid

3.5

LDL/HDL ratio is ____________ in healthy individuals

130

the maximum healthy LDL concentration is ________________ mg/dL

40

the minimum healthy HDL concentration is _________________ mg/dL

oxLDL (bad fat)

in hypercholesterolemia, there are not enough LDL receptors so the excess LDL that does not get endocytosis gets oxidized into ____________

foam cells

dead macrophages that have phagocytized oxLDL; accumulate on the inside of blood vessels, forming athrosclerotic plaques

UV light

converts 7-dehydrocholesterol into previtamin D2

Vitamin D3 (cholecalciferol)

previtamin D2 gets oxidized into _____________, an inactive prohormone

calcitriol

vitamin D3 (cholecalciferol) gets converted into _______________, the active hormone

products

vitamin D, steroid hormones, and bile salts are biosynthetic __________________ of cholesterol

number of carbons in pregnenolone, progestogens, mineralocorticoids, and glucocorticoids

progestagens

glucocorticoids, mineralocorticoids, and androgens are derived from _________________

estrogens

18 carbons; derived from androgens (19 C)

bile salts

emulsifying agents for enhancing the digestion/absorption of lipids (glycocholate and taurocholate)

monooxygenases

oxygen atoms are inserted in steroids by mixed function ____________________ for their metabolism

(Cytochrome P450)

sodium

counter ion of taurocholate