Fatty Acid Storage Flashcards
1
Q
fat storage is promoted by insulin
A
- adipocytes release lipoprotein lipase in response to insulin
- FA are unloaded from chylomicrons and VLDL and taken up by adipocytes
- insulin promotes uptake of both glucose and FA into adipocytes (via translocation of transport proteins from vesicles to the plasma membrane
- they glucose generates glycerol background needed to synthesize TG
- fat cells have everything they need to store TG
2
Q
NEFA
A
- released through action of lipoprotein lipase
- transported into adipocytes by FA transporters
- insulin promotes translocation of FA transporters to PM
- LCFA bound to ALBP
- in fat cell, used as fuel or stored as TG
- next step is conversion to fatty acyl CoA via thiokinase
3
Q
fat mobilization
A
- de-esterification
- lipolysis
- FA successively released from TG, DAG, and MAG by esterases
- hormone-sensitive lipase
4
Q
hormone sensitive lipase
A
- releases FA preferentially from DAG and MAG
- mainly responsible for catalyzing 2nd and 3rd steps, yielding NEFA and glycerol
- HSL has broad specificity, also releases FA more slowly from TG, as well as from retinyl esters and cholesteryl esters (CE)
- activated by catecholamines and glucagon
- found mainly in adipocytes and in cells that produce steroid hormones from CE
- mice deficient in HSL are lean and able to mobilize NEFA from fat stores: another enzyme must be rate limiting
5
Q
other fat releasing enzymes
A
- adipose triglyceride lipase- rate limiting step
- TG to DAG
- found in many tissues that can accumulate TG
- mice deficient in this enzyme become mildly obese, accumulating TG in multiple tissues, including cardiac muscle
6
Q
perilipins
A
- proteins that coat the surface of peripheral lipid droplets
- targets for cAMP dependent protein kinases (PKA)
- prior to hormone stim, access of HSL and other lipases prevented by perilipins
- phosphorylation of perilipins results in disruption of the sheet and lipases can gain access
- lipotransin helps HSL to dock
7
Q
lipid droplets
A
- lipid droplets have large, centrally located droplet and smaller peripheral droplets
- have specialized surface of phospholipids and proteins
- peripheral droplets are metabolically active in lipolysis
8
Q
glycerol made from TG
A
- not much glycerol kinase in adipocytes
- leaves cell via AQPad
- used to think it was for a commitment step
9
Q
futile TG synthesis
A
- as TG hydrolyzed, adipocytes upregulate GAP from lactate, pyruvate, and aa- makes more TG
- modulates rate of FA release
- FA removed from blood by various tissues and oxidized to yield ATP
10
Q
delta naming
A
- from COO- end
- used in discussing enzymes that desaturate, elongate, oxidize
11
Q
omega naming
A
- from methyl end
- 3 carbons between DBs
12
Q
omega 7 class
A
- palmitoleic
- 16:1 omega 7
13
Q
omega 9
A
- oleic
- 18: 1 omega 9
14
Q
omega 6
A
- linoleic
- 18:2 omega 6
- essential
15
Q
omega 3
A
- linolenic
- 18:3 omega 3
- essential
