Lipid Transport and Storage Flashcards
Which statement is incorrect?
A. Fat absorbed from the diet and lipids synthesized by the liver and adipose tissue must be transported between the various tissues and organs for
utilization and storage.
B. 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
chylomicrons
C. In a meal-eating omnivore such as the human, excess calories are ingested in the anabolic phase of the feeding cycle, followed by a period of
negative caloric balance when the organism draws on its carbohydrate and fat stores
D. Lipid is mobilized from adipose tissue as free fatty acids (FFAs) bound to serum albumin
B.
SHOULD BE
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
Lipoproteins mediate this cycle by transporting lipids from the intestines as
chylomicrons
Which statement is true?
A. excess calories are ingested in the anabolic phase of the feeding cycle, followed by a period of
negative caloric balance when the organism draws on its carbohydrate and
fat stores.
B. Lipoproteins mediate this cycle by transporting lipids from the intestines as chylomicrons
C. from the liver as very-low-density lipoproteins (VLDL)
D. to most tissues for oxidation and to adipose tissue
for storage
E. All of the above
F. None of the above
E. All of the above
Lipoproteins mediate this cycle by transporting lipids from the liver as
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 hyperlipoproteinemias.
The most common of these is in ______________ where insulin deficiency causes excessive
mobilization of FFA and underutilization of chylomicrons and VLDL, leading to hypertriacylglycerolemia
diabetes mellitus
insulin deficiency causes excessive
mobilization of FFA and underutilization of chylomicrons and VLDL, leading to ________
hypertriacylglycerolemia
Which is incorrect?
A. other pathologic conditions
affecting lipid transport are due primarily to inherited defects
B. Obesity—particularly facial obesity—is a risk factor for increased mortality, hypertension, type 2 diabetes mellitus, hyperlipidemia, hyperglycemia, and various endocrine dysfunctions.
C. Abnormalities of lipoprotein metabolism cause various hypo- or hyperlipoproteinemias
D. Inherited defect of lipid transport can cause hypercholesterolemia and premature atherosclerosis
E. All of the above
F. None of the above
B
SHOULD BE
Obesity—particularly ABDOMINAL obesity—is a risk factor for
increased mortality, hypertension, type 2 diabetes mellitus,
hyperlipidemia, hyperglycemia, and various endocrine dysfunctions.
LIPIDS ARE TRANSPORTED IN THE PLASMA
AS
LIPOPROTEINS
Four Major Lipid Classes Are Present in
Lipoproteins?
A. VLDL, cholesterol, steroids, glycophospholipids
B. Phospholids, cholesterol, LDL, VLDL
C. cholesteryl esters, triacylglycerols, phospholipids, cholesterol
D. triacylglycerols, phospholipids, steroids, cholesteryl esters,
C. cholesteryl esters, triacylglycerols, phospholipids, cholesterol
Plasma lipids consist of how many percent triacylglycerols
16%
Plasma lipids consist of how many percent cholesteryl esters
36%
Plasma lipids consist of how many percent phospholipids
30%
Plasma lipids consist of how many percent cholesterol
14%
how many percent of much smaller
fraction of unesterified long-chain fatty acids
4%
metabolically the most active of the plasma lipids.
unesterified long-chain fatty acids (FFA)
Which statement is incorrect?
A. fat is less dense than water
B. density of a lipoprotein increases as
the proportion of lipid to protein increases
C. Four major groups of lipoproteins have been identified that are important physiologically
D. Lipoproteins may also be classified according
to their electrophoretic properties into α- (HDL), β- (LDL), and pre-β (VLDL)-lipoproteins.
E. All of the above
F. None of the above
B
should be
the density of a lipoprotein decreases as
the proportion of lipid to protein 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
lowdensity lipoproteins (LDL)
involved in cholesterol transport and also in VLDL and chylomicron metabolism
high-density lipoproteins, (HDL)
predominant lipid in chylomicrons and VLDL
Triacylglycerol
___________ and _________are the predominant lipids in LDL and HDL
cholesterol and phospholipid
Lipoproteins may also be classified according
to their electrophoretic properties into, except:
a. α- (HDL)
b. β- (LDL)
c. pre-β (VLDL)-lipoproteins
d. α- (LDL)
d. α- (LDL)
TRUE OR FALSE
Fatty Acid Consist of a Nonpolar Core & a Single
Surface Layer of Amphipathic Lipids
FALSE
SHOULD BE
Lipoproteins Consist of a Nonpolar Core & a Single
Surface Layer of Amphipathic Lipids
__________ core consists of mainly triacylglycerol and
cholesteryl ester and is surrounded by a single surface layer of amphipathic phospholipid and cholesterol molecules
nonpolar lipid
Which statement is correct:
A. These are oriented so that their polar groups face outward to the aqueous medium, as in the cell membrane
B. The protein moiety of a lipoprotein is known as an apolipoprotein or apoprotein,
constituting nearly 70% of some HDL and as little as 1% of chylomicrons
C. Small amounts of cholesteryl ester and triacylglycerol are found in the surface layer and a little free cholesterol in the core.
D. All of the above
E. None of the above
D. All of the above
the protein moiety of a lipoprotein is known
apolipoprotein or apoprotein
TRUE OR FALSE:
The Distribution of Apolipoproteins Characterizes the
Lipoprotein
TRUE
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
The FFAs (also termed nonesterified fatty acids [NEFAs] or unesterified fatty acids)
Which is correct of FFA?
A. They are found in combination with albumin, a
very effective solubilizer
B. Levels are low in the fully fed condition and rise
to 0.7 to 0.8 mEq/mL in the starved state
C. In uncontrolled diabetes mellitus, the level may rise to as much as 2 mEq/mL.
D. FFAs are removed from the blood extremely rapidly by the tissues and oxidized (fulfilling 25-50% of energy requirements in starvation) or esterified to form triacylglycerol
E. All of the above
F. None of the above
E. All of the above
Which of the statement is incorrect?
A. In fed state, esterified lipids from the
circulation or in the tissues are also oxidized, particularly in heart and skeletal muscle cells, where considerable stores of lipid are found.
B. The FFA uptake by tissues is related directly to the plasma-FFA concentration, which in turn is determined by the rate of lipolysis in adipose tissue
C. After dissociation of the fatty acid–albumin complex at the plasma membrane, fatty acids bind to a membrane fatty acid transport protein that acts as a transmembrane cotransporter with Na+
D. On entering the cytosol, FFAs are bound by intracellular fatty acid–binding proteins.
E. All of the above
F. None of the above
A
SHOULD BE
In starvation, esterified lipids from the
circulation or in the tissues are also oxidized, particularly in heart and skeletal muscle cells, where considerable stores of lipid are found.
After dissociation of the fatty acid–albumin complex at the plasma membrane, fatty acids bind to a _________________ that acts as a transmembrane cotransporter with Na+.
membrane fatty acid transport protein
On entering the cytosol, FFAs are bound by __________________
intracellular fatty acid–binding proteins
Which is incorrect?
A. TRIACYLGLYCEROL IS TRANSPORTED FROM
THE INTESTINES IN CHYLOMICRONS
B. TRIACYLGLYCEROL IS TRANSPORTED FROM
THE LIVER IN VERY-LOW-DENSITY LIPOPROTEINS
C. TRIACYLGLYCEROL IS TRANSPORTED FROM
THE LIVER IN CHYLOMICRONS
D. ALL OF THE ABOVE
E. NONE OF THE ABOVE
C
SHOULD BE
TRIACYLGLYCEROL IS TRANSPORTED FROM
THE LIVER IN VERY-LOW-DENSITY LIPOPROTEINS
chylomicrons are found in _______ formed only by the
lymphatic system draining the intestine
chyle
WHICH STATEMENT IS CORRECT?
A. chylomicrons are found in chyle formed only by the
lymphatic system draining the intestine
B. They are responsible for the transport of all dietary lipids into the circulation
C. Small quantities of
VLDL are also to be found in chyle
D. most VLDL in the plasma are of hepatic origin
E. ALL OF THE ABOVE
F. NONE OF THE ABOVE
E. ALL OF THE ABOVE
Which of the following is not true?
A. The nonpolar lipid core consists of mainly triacylglycerol and cholesteryl ester and is surrounded by a double surface layer of amphipathic phospholipid and cholesterol molecules
B. They are oriented so that their polar groups face outward to the aqueous medium, as in the cell membrane
C. The protein moiety of a lipoprotein constituting nearly 70% of some HDL and as little as 1% of chylomicrons
D. Small amounts of cholesteryl ester and triacylglycerol are found in the surface layer and a little free cholesterol in the core.
E. All of the above
F. None of the above
A.
The nonpolar lipid core consists of mainly triacylglycerol and cholesteryl ester and is surrounded by a SINGLE surface layer of amphipathic phospholipid and cholesterol molecules
Which statetement is incorrect?
A. One or more apolipoproteins are present in each lipoprotein and are usually abbreviated as apo followed by the letter A, B, C,
B. Some apolipoproteins are integral and cannot be removed (eg, apo B), whereas others are bound to the surface and are free to transfer to other lipoproteins, eg, apos C and E).
C. The major apolipoproteins of HDL (α-
lipoprotein) are apo As
D. The main apolipoprotein of LDL (β-
lipoprotein) is apo B (B-100), which is found also in VLDL
E. All of the above
F. None of the above
F. None of the above
example of apolipoproteins that are integral and cannot be removed
apo B
example of apoproteins that are bound to the surface and are free to transfer to other
lipoproteins
apos C and E
The major apolipoproteins of HDL (α-
lipoprotein) are?
apo As
The main apolipoprotein of LDL (β-
lipoprotein) is?
apo B (B-100)
apolipoprotein that is also found in VLDL
apo B (B-100)
It contai a truncated form (48% of apo B-100) of apo B (B-48) that is synthesized in the intestine, while B-100 is synthesized in the liver.
Chylomicrons
one of the longest single polypeptide chains known, having 4536 amino acids and a molecular mass of 550,000 Da
Apo B-100
Which of the following is correct?
A. To produce Apo B-48, a stop signal is introduced into the mRNA transcript for apo B-100 by an RNA editing enzyme
B. Apos C-I, C-II, and C-III are smaller polypeptides
(molecular mass 7000-9000 Da) freely transferable between several different lipoproteins
C. Apo E, 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
D. All of the above
E. None of the above
D. All of the above
Apolipoproteins carry out several roles except:
A. they can form part of the structure of the lipoprotein, for example, apo B
B. they are enzyme cofactors, for example, C-II for lipoprotein lipase, A-I for lecithin:cholesterol acyltransferase (LCAT), or enzyme inhibitors, for
example, apo A-II and apo C-III for lipoprotein lipase, apo C-I for cholesteryl ester transfer protein
C. they act as ligands for interaction
with lipoprotein receptors in tissues, for example, apo B-100 and apo E for the LDL receptor, apo E for the LDL-receptor–related protein-1 (LRP-1),
which recognizes remnant lipoproteins (see below), and apo A-I for the HDL receptor.
D. Apo D is thought to have a role in chylomicron
metabolism and may also act as a regulator of satiety and glucose homeostasis, making it a potential therapeutic target for the treatment of
diabetes and obesity, while apo A- IV is believed to be an important factor in human neurodegenerative disorders.
E. All of the above
F. None of the above
D.
SHOULD BE
Apo A-IV is thought to have a role in chylomicron
metabolism and may also act as a regulator of satiety and glucose homeostasis, making it a potential therapeutic target for the treatment of diabetes and obesity, while apo D is believed to be an important factor in human neurodegenerative disorders.
THEY ARE RAPIDLY
METABOLIZED
FREE FATTY ACIDS
True of fatty acids except:
A. The FFAs (also termed esterified fatty acids [EFAs] or esterified fatty acids) 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.
B. They are found in combination with albumin, a
very effective solubilizer.
C. Levels are low in the fully fed condition and rise
to 0.7 to 0.8 mEq/mL in the starved state.
D. FFAs are removed from the blood extremely rapidly by the tissues and oxidized (fulfilling 25-50% of energy requirements in starvation) or esterified to form triacylglycerol
E. All of the above
F. None of the above
A.
SHOULD BE
The FFAs (also termed nonesterified fatty acids [NEFAs] or unesterified
fatty acids) 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
Which statement is incorrect?
A. In starvation, esterified lipids from the circulation or in the tissues are also oxidized, particularly in heart and skeletal muscle cells, where considerable stores of lipid are found.
B. The FFA uptake by tissues is related directly to the plasma-FFA concentration, which in turn is determined by the rate of lipolysis in adipose tissue.
C. After dissociation of the fatty acid–albumin complex at the plasma membrane, fatty acids bind to a membrane fatty acid transport
protein that acts as a transmembrane cotransporter with Ca+.
D. On entering the cytosol, FFAs are bound by intracellular fatty acid–binding proteins.
E. All of the above
F. None of the above
C.
should be
After dissociation of the fatty acid–albumin complex at the plasma membrane, fatty acids bind to a membrane fatty acid transport
protein that acts as a transmembrane cotransporter with Na+.
_____ are found in chyle formed only by the
lymphatic system draining the intestine and are responsible for the transport of all dietary lipids into the circulation
chylomicrons
most _____________ in the plasma
are of hepatic origin.
VLDL
They are the vehicles of transport of triacylglycerol from the liver to the extrahepatic tissues.
VLDL
All are correct except:
A. Newly secreted or “nascent” chylomicrons and VLDL contain only a small amount of apolipoproteins a and b, and the full complement is acquired from HDL in the circulation
B. Apo B, is an integral part of the lipoprotein particles. It is incorporated into the particles during their assembly inside the cells and is essential for
chylomicron and VLDL formation.
C. In abetalipoproteinemia (a rare
disease), lipoproteins containing apo B are not formed and lipid droplets accumulate in the intestine and liver.
D. All of the above
E. None of the above
A
should be
Newly secreted or “nascent” chylomicrons and VLDL contain
only a small amount of apolipoproteins C and E, and the full complement
is acquired from HDL in the circulation
a rare disease in which lipoproteins containing apo B are not formed and lipid droplets accumulate in the intestine and liver.
abetalipoproteinemia
Which of the following is incorrect?
A. Apolipoprotein B, synthesized in the RER, is incorporated into particles with triacylglycerol, cholesterol, and phospholipids in the SER
B. After the addition of carbohydrate residues in Golgi Apparatus, they are released from the cell by reverse pinocytosis
C. Chylomicrons pass into the digestive system.
D. VLDL are secreted into the space of Disse and then into the hepatic sinusoids through fenestrae in the endothelial lining.
E. All of the above
F. None of the above
C.
should be
Chylomicrons pass into the lymphatic
system
Which type of lipoproteins is rapidly catabolized?
A. CHYLOMICRONS & HDL
B. TRIGLYCERIDES & CHYLOMICRONS
C. LDL & HDL
D. CHYLOMICRONS & VERY-LOW-DENSITY
LIPOPROTEINS
D. CHYLOMICRONS & VERY-LOW-DENSITY
LIPOPROTEINS
Which of the statement is incorrect?
A. The clearance of chylomicrons from the blood is rapid, the half-time of disappearance being under 1 hour in humans
B. Larger particles are catabolized more quickly than smaller ones.
C. Fatty acids originating from chylomicron triacylglycerol are delivered mainly to the liver (80%), and ~20% goes to adipose tissue, heart, and muscle
C
should be
Fatty acids originating from chylomicron triacylglycerol are delivered mainly to adipose tissue, heart, and muscle (80%), while ~20% goes to the liver
Which statement is correct?
A. the liver does not metabolize native chylomicrons or VLDL significantly
B. the liver does metabolize native chylomicrons or VLDL significantly
C. the fatty acids in the intestines must be secondary to the metabolism in extrahepatic tissues.
D. All of the above
E. None of the above
A
the liver does not metabolize native chylomicrons or VLDL significantly; thus, the fatty acids in the liver must be secondary to their metabolism in extrahepatic tissues.
an enzyme located on the walls of blood capillaries,
anchored to the endothelium by negatively charged proteoglycan chains of heparan sulfate.
Lipoprotein lipase
TRUE OR FALSE?
Triacylglycerols of chylomicrons & VLDL are hydrolyzed by lipoprotein lipase to form remnant lipoproteins
TRUE
True of Lipoprotein lipase:
A. It has been found in heart, adipose tissue, spleen, lung, renal medulla, aorta, diaphragm, and lactating mammary gland, although it is not active in adult liver
B. It is not normally found in blood; however,
following injection of heparin, lipoprotein lipase is released from its heparan sulfate–binding sites into the circulation
C. Hepatic lipase is bound to the sinusoidal surface of liver cells and is also released by heparin
D. Both phospholipids and apo C-II are required as cofactors for lipoprotein lipase activity, while apo A-II and apo C-III act as inhibitors
E. All of the above
F. None of the above
E. All of the above
bound to the sinusoidal surface of liver cells and is also released by heparin.
Hepatic lipase
This enzyme does not react readily with chylomicrons or VLDL but is involved in chylomicron remnant and HDL metabolism
Hepatic lipase
are required as cofactors for lipoprotein lipase activity
phospholipids and apo C-II
apo A-II and apo C-III act as
inhibitors.
