Ch 25 - Lipid Transport And Storage Flashcards
Fat absorbed from the diet and lipids synthesized by the _________ and adipose tissue must be transported between the various tissues and organs for utilization and storage.
liver
Since lipids are insoluble in water, the problem of how to transport them in the aqueous blood plasma is solved by associating nonpolar lipids (triacylglycerol and cholesteryl esters) with amphipathic lipids (phospholipids and cholesterol) and proteins to make ___________________.
water-miscible lipoproteins
In a meal-eating omnivore such as the human, excess calories are ingested in the _________ phase of the feeding cycle, followed by a period of negative caloric balance when the organism draws upon its carbohydrate and fat stores.
anabolic
Lipoproteins mediate this cycle by transporting lipids from the intestines as ______________ —and from the liver as __________________—to most tissues for oxidation and to adipose tissue for storage.
chylomicrons
very low density lipoproteins (VLDL)
Lipid is mobilized from adipose tissue as free fatty acids (FFAs) bound to serum _______________.
albumin
Abnormalities of lipoprotein metabolism cause various hypo- or hyperli-poproteinemias. The most common of these is in _____________, where insulin deficiency causes excessive mobilization of FFA and underutilization of chylomicrons and VLDL, leading to ___________________.
diabetes mellitus
hypertriacylglycerolemia
Most other pathologic conditions affecting lipid transport are due primarily to inherited defects, some of which cause _________________ and premature ______________.
hypercholesterolemia
atherosclerosis
___________—particularly ______________ —is a risk factor for increased mor-tality, hypertension, type 2 diabetes mellitus, hyperlipidemia, hyperglycemia, and various endocrine dysfunctions.
Obesity
abdominal obesity
Lipids are transported in the plasma as _____________.
Lipoproteins
Plasma lipids consist of triacylglycerols (____%), phospholip-ids (____%), cholesterol (___%), and cholesteryl esters (____%) and a much smaller fraction of unesterified long-chain fatty acids (free fatty acids or FFA) (____%).
16% 30% 14% 36% 4%
The _________ is metabolically the most active of the plasma lipids
FFA
Since fat is less dense than water, the density of a lipoprotein _____________ as the proportion of lipid to protein __________.
Decreases
Increases
Derived from intestinal absorption of triacylglycerol and other lipids.
Chylomicrons
Derived from the liver for the export of triacylglycerol.
VLDL
Representing a final stage in the catabolism of VLDL.
LDL
Involved in cholesterol transport and also in VLDL and chylomicron metabolism.
HDL
____________ is the predominant lipid in chylomicrons and VLDL.
Triacylglycerol
Cholesterol and phospholipid are the predominant lipids in ______ and ______ respectively.
LDL and HDL
Lipoproteins may also be classified according to their electrophoretic properties into ____ (HDL), ____- (LDL), and ______ (VLDL)-lipoproteins.
Alpha
Beta
Pre-beta
___________ consists of nonpolar core and a single surface layer of ampiphatic lipids.
Lipoproteins
The _____________ consists of mainly triacylglycerol and cholesteryl ester and is surrounded by a single surface layer of amphipathic phospholipid and cholesterol molecules.
nonpolar lipid core
The protein moiety of a lipoprotein is known as an ___________________, constituting nearly 70% of some HDL and as little as 1% of chylomicrons.
apolipoprotein or apoprotein
Some apolipoproteins are integral and cannot be removed (eg, __________), whereas others are bound to the surface and are free to transfer to other lipoproteins, eg, ___________).
apo B
apos C and E
The major apolipoproteins of HDL (α-lipoprotein) are ________.
apoAs
The main apolipoprotein of LDL (β-lipoprotein) is _________, which is found also in VLDL.
apo B (B-100)
Chylomicrons contain a truncated form of apo B (B-48) that is synthesized in the _________, while B-100 is synthesized in the ___________.
Intestine
liver
____________ is one of the longest single polypeptide chains known, having 4536 amino acids and a molecular mass of 550,000 Da.
Apo B-100
___________ (48% of B-100) is formed after transcription of the apo B-100 gene by the introduction of a stop signal into the mRNA transcript by an RNA editing enzyme.
Apo B-48
__________, _________, and _______ are smaller polypeptides (molecular mass 7000-9000 Da) freely transferable between several different lipoproteins.
Apos C-I, C-II, and C-III
_________, found in VLDL, HDL, chylomicrons, and chylomicron remnants, is also freely transferable; it accounts for 5% to 10% of total VLDL apolipoproteins in normal subjects.
Apo E
Apolipoproteins carry out several roles: they can form part of the structure of the lipoprotein, for example ________.
Apo B
They are enzyme cofactors, for example:
_____ for lipoprotein lipase
_____ for lecithin:cholesterol acyltransferase
or enzyme inhibitors, for example:
__________ and _________ for lipoprotein lipase
__________for cholesteryl ester transfer protein
CII
A-I
Apo A-II and Apo C-III
Apo C-I
They act as ________ for interaction with lipoprotein receptors in tissues:
________ and ________ for the LDL receptor
________ for the LDL-receptor-related protein-1 (LRP-1) which has been identified as the remnant receptor
________ for the HDL receptor.
Ligands
Apo B-100 and Apo-E
Apo E
Apo A-I
_____________ is believed to be an important factor in human neurodegenerative disorders.
apo D
The ____________ also termed _____________ arise in the plasma from the breakdown of triacylglycerol in adipose tissue or as a result of the action of lipoprotein lipase on the plasma triacylglycerols.
FFAs (also termed nonesterified fatty acids [NEFAs] or unesterified fatty acids)
They are found in combination with __________, a very effective solubilizer, in concentrations varying between 0.1 and 2.0 meq/mL of plasma.
albumin
Levels are low in the fully fed condition and rise to __________ meq/mL in the starved state
0.7 to 0.8
In uncontrolled diabetes mellitus, the level may rise to as much as ___ meq/mL.
2
FFAs are removed from the blood extremely rapidly and oxidized (fulfilling _________% of energy requirements in starvation) or esterified to form triacylglycerol in the tissues.
25%-50%
In starvation, esterified lipids from the circulation or in the tissues are oxidized as well, particularly in ___________ and ___________, where considerable stores of lipid are to be found.
heart and skeletal muscle cells