Fat Metabolism INCOMPLETE NOTES Flashcards
why are lipids good as an energy store? (2)
what is lipoylsis? (2)
where does it mainly occur? (1)
what conditions needed for lipolysis? (1)
lipids good energy store bc:
- high density of energy in small space
- **limitless storage capacity
-**
lipolysis: break down of lipids into glycerol (1) & fatty acid tails (1)
- location: adipose tissues
- conditions: aerobic conditions
which is the main hormone that regulates lipolysis?
which hormones activate this ^ hormone?
which hormone inhibits 1?
- hormone sensitive lipase (HSL; aka diglyceride lipase) regulates lipolysis
HSL:
- activated by: adrenaline and noradrenaline
- inhibited by: insulin
HSL is:
- activated by: adrenaline and noradrenaline
- inhibited by: insulin
explain how this occurs xox
HSL:
- activated by: adrenaline and noradrenaline
- inhibited by: insulin
Adrenaline & noradrenlaine activates HSL by:
- activating cAMP signalling.
- cAMP signalling activates protein kinase
- protein kinase phosphorylates HSL = active
- HSL breaks down triglycerides into glycerol & fatty acids
insulin inhibits HSL by:
- blocks cAMP signalling (by activating phosphodiesterases - breaks down cAMP)
- this keeps HSL de-phosphorylated & inactive
which other enzyme regulates lipolysis?
which enzyme regulates ^?
- adipose triglyceride lipase (ATGL): breaks down triglycerides to diglycerides & FA.
- ATGL is regulated separately from HSL and activated by glucagon via cAMP
triglycerides are broken down into fatty acids and glycerol.
- once free, fatty acids are transported in the blood attached to which protein?
- why cant they go around on their own?
* what are FA used to make ? *
during lipolysis, triglycerides are broken down into fatty acids and glycerol:
- once free, fatty acids are transported in the blood attached to albumin
- why cant they go around on their own? bc free FA in blood are toxic
- FA are used to produce acetyl Co-A
triglycerides are broken down into fatty acids and glycerol. fatty acids are then used to make acetyl co-A.
what is the three step process in which this occurs?
- FA –> fatty acyl-CoA (via enzyme: acyl-coA synthase). @ outer mt. membrane.
- fatty acyl-CoA transported into mt matrix by the carnitine shuttle
- Beta-oxidation of fatty acyl-CoA = acetyl Co-A + NADH/FADH2 (& goes onto krebs cycle)
triglycerides are broken down into fatty acids and glycerol. fatty acids are then used to make acetyl co-A.
the second step of this it the cartinine shuttle. explain how this occurs !
- fatty acyl Co-A reacts with cartinine (via enzyme cartinine acyl transferase) to produce cartinine-linked-fatty acyl & Co-A is released
- cartinine-linked-fatty-acyl is transferred across the inner mt. membrane into the matrix (via ezyme **translocase)
- cartinine-linked-fatty-acyl**
reacts with Co-A to reproduce fatty acyl Co-A. released cartinine goes back out of IMM & does this again
(fatty acyl Co-A undergoes beta oxidation & turns into acetyl-co-A)
at which stage of FA break down does regulation most commonly occur at?
the cartinine shuffle !
triglycerides are broken down into fatty acids and glycerol. fatty acids are then used to make acetyl co-A.
the second step of this it the cartinine shuttle. explain how regulation of this step occurs :) (what inhibits the step (2) ? what activates it?)
the cartinine shuffle:
short term:
- activated by: glucagon through cAMP signalling (+ CAT1 (cartinine acyl transferase))
- inhibited by: malonyl Co-A & insulin ( - CAT1 (cartinine acyl transferase))
long term:
- changes in expression of CAT1 (cartinine acyl transferase) / CPT1
triglycerides are broken down into fatty acids and glycerol. fatty acids are then used to make acetyl co-A.
the second step of this is the beta oxidation of acyl-CoA. explain how this occurs !
- what does it produce?
Beta oxidation of fatty acyl-CoA
- removal of carbons from the long chain of FA to give acetyl Co-A with each 2 carbons removed.
- involves 4 cycle reactions for one FA:
a) each cycle involves: oxidation, hydrolysis, oxidation, thiolysis (OHOT).
b) at the end of each cycle = left with acyl-Co-A which has been stripped of the fatty acyl
?????????????????????//////????????????
- creates
a) Acetly Co-A
b) FADH2
c) NADH
go over how many products of B oxidation are made !!
B-oxidation occurs in most tissues except the brain (3) and RBC (1) why?
B-oxidation occurs in most tissues except the brain and RBC. why?
- *brain:**
- ATP production from adipose tissue derived FA = slower c.f. blood glucose
- (ATP generation is linked to B-oxidation of FA), which requires more O2 than glucose does. enhances the risk of hypoxia in brain
- B-oxidation of FA creates super oxides -> can creates severe ox. stress :(
- *rbc:**
- have no mt.
explain the process of lipogenesis
lipogensis = glucose –> FA to form fat
- glucose undergoes glycolysis to form pyruvate
-
pyruvate goes through pyruvate dehydrogenase to form acetyl co-A (ordinarily would go into Krebs cycle)
3. instead - citrate leaves the krebs cycle & leaves mt & into cytosol
4, ATP-citrate lyase breaks down citrate to produce acetyl co-A - acetyl co-A reactes with HCO3- & ATP to form malonyl CoA.
-
malonyl CoA used to make palmitic acid
7 palmitic acid goes through 4 repeated steps to create growing FA chain via Fatty acid synthase (growing FA chain increases by 2 carbons each time)
fatty acid synthesis 4 steps per cycle
