(17) Lipids and Lipoproteins (Zaidi) Flashcards
Describ how TAGs are such good sources of energy!
Triacylglyercols contain about 6.75 tims as much energy as carbs!
100,000 kCal in TAGs
Name the structures
Sources of Triacylglycerols?
Dietary TAG
De Novo TAG (hepatocytes)
De Novo TAG (adipocytes)
Describe TAG synthesis in intestinal cells:
- Dietary TAGs broken down to monoacylglycerol (MAG) and FFA in intestinal lumen by pancreatic lipases
- Intestinal cells resynthesize TAGs using MAG as backbone and adding 2 FFAs
- TAGs packaged to form chylomicron
- Chylomicrons released into lymphatic system and enter blood via thoracic duct
*TAG SYNTHESIS IN INTESTINAL CELLS PROMOTED BY DIETARY TAGS
What feeds TAG synthesis in the liver?
Glucose
*De Novo synthesis in hepatocytes
***PROBABLY A TEST QUESTION
If you want to inhibit the conversion of glycerol into TAG in the hepatocyte, and it will not affect other pathways…which would you pick?
Glycerol Kinase!!!
Describe the key points of TAG Synthesis in the liver
- Glucose and Glycerol form G3P
- G3P used as backbone for TAG synthesis
- FFA (synthesized in liver from acetyl CoA) added to G3P to form TAGS
- TAGs packaged, form VLDL
- VLDL released into bloodstream
*TAG SYNCHESIS IN HEPATOCYTES PROMOTED BY EXCESS CARBS
Describe TAG synthesis in Adipocytes
- Glucose forms G3P
- G3P used as backbone for TAG synthesis
- FFA (from chylomicrons and VLDL in blood) by action of capillary lipoprotein lipase
- G3P and FFA form TAGs
- TAGs stored in adipocytes
*TAG synthesis in adipocytes promoted by excess carbohydrates and fats
Describe how TAG synthesis in intestinal cells, hepatocytes and adipocytes are connected:
Product of Intestinal cells = Chylomicron
Product of Hepatocytes =VLDL
Combine together to provide fuel for adipocyte TAG synthesis
Fatty acids broken down via ___________ in __________ to produce energy
Beta-oxidation, Mitochondria
Describe mobilization of fatty acids in adipocytes
- 4 major lipases (ATGL, HSL, LPL, MAG lipase)
- Release of fatty acids
- Transport of fatty acids (short can travel alone, long complex with albumin for transport)
CORRELATION BOX
Activity of HSL modulated by
Phosphorylation
CORRELATION BOX
What are major controllers of HSL?
ACTIVATE MOBILIZATION: Glucagon, Epinephrine
*Both phosphorylate HSL (activate it) and promote lipolysis in adipocytes
FED STATUS inhibits mobilization of TAGs (insulin)
What is perilipin?
Family of proteins that coat lipid droplets in adipocytes and muscle cells
Regulate lipolysis by controlling physical access to HSL
Target of obesity treatment
What transport TAGs and Cholesterol?
Lipoproteins
What is the substrate for cholesterol biosynthesis?
Acetyl CoA
What is “bad” cholesterol?
Low density lipoproteins (LDL)
What is “good” cholesterol?
High density lipoproteins (HDL)
What is the largest lipoprotein? Smallest?
Largest = chylomicron
Smallest= HDL
What are the 3 types of Apo proteins on chylomicrons?
ApoB-48
ApoC-II
ApoE
How many apo proteins does each lipoprotein have?
VLDL
IDL
LDL
HDL
VLDL (3)
IDL (2)
LDL (1)
HDL (3)
What are the specific surface apo proteins in:
VLDL
IDL
LDL
HDL
VLDL: ApoB-100, ApoC-II, ApoE
IDL: Apo B-100, Apo E
LDL: Apo E
HDL: ApoA-I, ApoC-II, ApoE
Why is HDL “good” cholesterol?
High protein and phospholipid content
What does LCAT do?
Participates in HDL processing
Lecithin cholestrol acyl transferase:
Helps supply cholesterol to other lipoprotein
