Class 5: Lipid Metabolism 1 Flashcards
Lingual and gastric lipase affect what FAs?
Short and medium chain FA in TAG
Suspension into small particles in the aqueous environment
Emulsification
Emulsifiers thatre amphipathic
Bile salts
Contraction of the GB to release bile salts and other pancreatic enzymes is stimulated by the gut hormone:
Cholecystokinin
Digests all lengths of FA, Forms FA and 2-monoacylglycerol (2-MAG)
Pancreatic lipase
Pancreas produces _______ which removes FA from cholesterol esters
Esterase
Recognized by receptors on surface of liver cells allowing endocytosis
ApoE
IDL
Activates lipoprotein lipase present on capillary endothelial cells in muscle and adipose tissue which digests chylomicrons
ApoCII
VLDL
Released in response to acidic material.
Causes release of HCO3 which increases the pH to 6, optimal for intestinal enzymes.
Secretin
Removes FA from phospholipids
Phospholipase A2
These FA are absorbed directly into portal blood from intestinal epithelial cells
Short and medium chain FA
TAG form micelles in intestinal lumen. Emulsified by bile salts. Absorbed acros microvili. Then the FAs and 2-MAGs are condensed again back to TAG and are packaged into chylomicrons. What is the major protein expressed on the outside of the chylomicron?
Apoprotein B48
Where do the apolipoproteins (chylomicrons) take the TAG stores?
To the lymph system.
Freshly made chylomicrons
Nascent chylomicrons
Secreted y intestinal epithelial cells via exocytosis into the lymph system
Nascent chylomicrons
Where does the chylomicrons enter the blood?
Thoracic duct - into the L brachiocephalic vein
Nascent chylomicrons become mature chylomicrons when:
Nascent accepts proteins from HDLs
Located on the surface of cells
Hydrolyzes the TG in the chylomicrons so they may be sent across plasma membrane into adipocytes
Lipoprotein lipase
Utilization of FA req’s 3 steps:
- Mobilization- TAGs in adipose are broken to FA and glycerol, released and transported to tissues in need of energy.
- Activation- FAs 1st activated and transported to mito.
- Degradation- stepwise breakdown of FA into acetyl CoA which is then processed in TCA.
After mobilization, glycerol can be used:
In glycolysis to form pyruvate
Or
Gluconeogenesis to form glucose.
Both in the LIVER
After mobilization, what happens to the FA from the adiposcyte?
It can be sent to tissue requiring energy and enter into the FA oxidation = then to TCA
What is req’d for glycerol to be used in the liver…what enzyme?
Glycerol kinase after this reaction…
Glycerol can be taken into glycolysis,gluconeogenesis, or TAG synthesis.
Activation of FA p/t oxidation:
FA becomes acyl Coa (forms a thioester bond) by Acyl-Coa Synthetase by a 2 step process req’s ATP
Can the activation step be reversed in FA oxidation?
No it is irreversible b/c ATP hydrolysis –PPi hydrolysis makes it irreversible
Once activated, how does call Coa enter the mito?
Carnitine translocase
Steps in beta oxidation:
Acyl Coa OXIDIZED to trans-∆2-enoyl CoA by acyl CoA dehydrogenase
Trans-∆2-enoyl CoA HYDRATED to L-3-hydroxyacyl CoA by enoyl CoA hydratase
L-3-hydroxyacyl CoA OXIDIZED to 3-ketoacyl CoA by hydroxy acyl CoA dehydrogenase
3-ketoacyl CoA THIOLYZED to Acyl CoA and acetyl CoA by ketothiolase
How many ATP for palmitate?
106 ATP (108 - 2 ATP for activation
Odd numbered = FA requires:
Ex: palmitoleoyl CoA
Isomerase
[cis-∆3-enoyl CoA isomerase]
Even numbered = FA requires
Ex: linoleoyl CoA
Isomerase and reductase
Cis-∆3-enoyl CoA isomerase
2,4-dienoyl CoA reductase
Even numbered = FA gives rise to:
Where does this product travel?
Propionyl CoA and acetyl CoA
Propionyl CoA is converted to succinyl CoA which then enters the TCA cycle [this conversion req’s Vit B-12 (cobalamin)]
What happens to acetyl coa from FA degradation ?
Entered TCA cycle if there is adequate OAA
If there isn’t OAA, acetyl CoA s not utilized (fats burn in the flame of carbs)–fats aren’t able to be used and ketone bodies accumulate
3 names for ketone bodies.
Acetoacetate
D-3-hydroxybutyrate
Acetone
How to get acetyl CoA from acetoacetate?
2 enzymes?
Acetoacetate converted to acetoacetyl CoA by CoA transferase
Acetoacetyl CoA converted to 2 acetyl CoA by thiolase
