Lipids and Lipoproteins Flashcards Preview

Clinical Chemistry > Lipids and Lipoproteins > Flashcards

Flashcards in Lipids and Lipoproteins Deck (82)
Loading flashcards...

These provide the transportation system for different types of water insoluble fatty substances



How are fats absorbed from diet and lipids synthesized by liver and adipose tissues, transported in the aqueous blood plasma?

associating non-polar lipids (triacylglycerol and cholesterol esters) with amhipathic lipids (phospholipids and cholesterol) and proteins to make water-miscible proteins


How do lipoproteins mediate the production of water-miscible lipoproteins?

They transport lipids from the intestine as chylomicrons and from the liver as very low density lipoproteins (VLDL) to most tissues for oxidation and to adipose tissue for storage.


What happens to excess calories in humans?

ingested in anabolic phase of feeding cycle followed by negative caloric balance when organism draws upon its carbohydrates and fat stores


How is lipid mobilized from adipose tissue?

as free fatty acid attached to serum albumin


What is the purpose of lipoproteins?

transport hydrophobic lipid (fat) molecules in water, as in blood or extracellular fluid


What specifically comprises lipoproteins?

single layer phospholipid and cholesterol outer shell
*with non-polar core and single surface layer of amphipathic lipids


What consists the lipophilic or hydrophobic portions of each molecule?

Triacylglycerol and cholesteryl ester surrounded by a single surface layer of amphipathic phospholipids and cholesterol molecules


Lipoproteins may be separated according to what?

electrophoretic properties (alpha (-), beta (-) and pre beta (-) lipoproteins


T or F: the density of a lipoprotein decreases as the proportion of lipid to protein increases



types of lipoproteins

very high density lipoproteins
low density lipoproteins


lipoprotein which is the biggest and derived from intestinal absorption of triacylglycerol and other lipids


(primary concentration of fat that travel to different tissues)


Chylomicrons are responsible for transport of what

dietary tryiglycerides (exogenous) from the GI tract to liver to skeletal muscle and to adipose tissue


Composition of chylomicrons

Cholesterol at core
Triglycerides (90-95%)
Protein (added by liver; if fats arent attached to proteins, lipoproteins should be increased like apolipoprotein B)


What happens after eating high fat food?

fat is emulsified by pancreatic lipase, increasing the surface area for absorption through the enterocyte.
*intestinal lining contains receptors that absorb the esterified fat afte which, it goes to the blood then most of it goes to the liver


[Synthesis of chylomicrons]
1. -2. Where are lipid components assembled?

SER and golgi apparatus of mucosal cells with apoproteins (B-48 and A-apolipoprotein) synhesized in RER


[Synthesis of chylomicrons]
3. The assembled lipid components are called?

nascent chylomicrons
*exocytosed into the lacteals of the intestinal villi; appear only after meals rich in fats


[Synthesis of chylomicrons]
4. How do nascent chylomicrons reach general circulation?

from lymph vessels (lacteals) via thoracic duct


[Synthesis of chylomicrons]
5. When are dietary lipids incorporated in chylomicrons?

following absorption in intestine


[Metabolism of chylomicrons]
1-2. What do the initial chylomicrons (synthesized by intestinal cells and only contain apoB-48 and apo A) acquire upon entering circulation?

apo C-II and apo E from plasma HDL to form mature chylomicrons


[Metabolism of chylomicrons] 3-4. T or F: apo E activates the enzyme lipoprotein lipase which causes hydrolysis of about 80-90% of the chylomicron triacylglycerols in the peripheral tissue such as muscles and adipose tissue

False, apo C-II


[Metabolism of chylomicrons]
5. What accompanies hydrolysis of chylomicron triacylglycerols?

transfer of most of the A and C-apolipoproteins to HDL.

*changes convert chylomicrons into smaller particles (chylomicron remnants)


[Metabolism of chylomicrons]
7. What happens to the fatty acids and glycerol released from the hydrolyzed triacylglycerols

FA: enter muscle and adipose tissue cells
Glycerol: enters the liver where it is used for synthesis of TAG


[Metabolism of chylomicrons] What happens to chylomicron remnants?

1. removed from blood circulation by liver
2. bind to lipoprotein receptors on surface of hepatocytes
3. whole remnant particle is taken by hepatocyte via endocytosis


[Fate of chylomicron remnants] What happens to intracellularly endocytosed vesicles?

carried to lysosomes where they are degraded to release the constituents


T or F: Chylomicrons are usually present in plasma after fasting

False, removed from plasma within 6 hours by liver (inadequate clearance = creamy layer on plasma)


VLDLs are secreted directly into the blood of liver as?

nascent VLDL particle containing Apo B-100 which obtain Apo C-II and Apo E from circulating HDL


VLDLs are used in transporting what?

*50-65% = triglyceride
(can be from excess dietary carbs converted in liver)

endogenous triglycerides from liver to tissues for storage energy and newly synthesized triglycerides from liver to adipose tissue


These are also known as B-Lipoproteins and the most atherogenic lipoproteins which represents a final stage in catabolism of VLDL

*50% = cholesterol


*transport cholesterol from liver to peripheral tissues
*synthesized in liver
*not in blood for long (need 12 hrs for test)


These lipoproteins are involved in VLDL and chylomicron metabolism and collect fat molecules from body's cells/tissue to the liver

High Density Lipoproteins

*also synth in liver (but also in intestine)
*modulates VLDL in liver