Lipid digestion, absorption and transport Flashcards
What happens to Virgin Coconut Oil (medium chain fatty acid) during digestion?
A. it gets readily absorbed in the body
B. it is transported in the body by albumin
C. it is brought to the liver via the portal vein where it will be oxidized
D. All of the above
D
Which of the following lipoprotein particles contains the greatest amount of lipids as percentage of weight?
A. Chylomicrons
B. VLDL
C. LDL
D. HDL
A
Which apoprotein is LDL’s marker?
A. A1
B. B48
C. B100
D. E
C
Reverse cholesterol transport is catalyzed by LCAT. What
apoprotein serves as cofactor for this enzyme?
A. Apo AI
B. Apo CII
C. Apo CIII
D. Apo E
A
Cells metabolize LDL via receptor mediated endocytosis. LDL receptors respond to specific apolipoproteins. The apoprotein with the highest affinity to LDL receptors is?
A. apoprotein B100
B. apoprotein CI
C. apoprotein CII
D. apoprotein E
A
What food should you eat if you want to decrease your cholesterol levels?
A. Cassava
B. Oat bran
C. White rice
D. Bread
B
Bab was curious to know what her cholesterol profile was after listening to the lecture on lipid digestion. She knows that hypercholesterolemia runs in her family. She had a fasting lipid profile done at PGH and the results were as follows:
Total cholesterol: 300 mg/dl
HDL: 65 mg/dl
Triglycerides: 175 mg/dl
However, there was no mention of the LDL level. Help Bab compute for her LDL value.
A. LDL = 190 mg/dl
B. LDL = 410 mg/dl
C. LDL = 112 mg/dl
D. LDL = 200 mg/dl
D
What is the only mechanism by which cholesterol is excreted in the human body?
A. Via the secretion of sweat
B. Via the synthesis of lipoproteins
C. Via the formation of bile salts
D. Via the secretion of lipases
C
Which of the following organs receives the LEAST amount of fatty acids from the hydrolysis of chylomicrons by lipoprotein lipase?
A. Heart
B. Adipose tissue
C. Skeletal muscles
D. Liver
D
Which of the following apoproteins is important in the degradation of LDL in the liver by serving as the recognition protein of the LDL receptor?
A. Apo B-48
B. Apo B-100
C. Apo C-I
D. Apo E
B
Which of the following lipoproteins is synthesized by both the liver and the intestines?
A. Chylomicrons
B. VLDL
C. LDL
D. HDL
D
Which of the following statements regarding the digestion and absorption of cholesterol is FALSE?
A. Liver synthesis of cholesterol exceeds the amount of cholesterol obtained from the diet
B. Fifty percent of cholesterol that enters the ileum is absorbed in the body.
C. Dietary cholesterol is incorporated into micelles together with triglycerides.obtained from the diet.
D. Cholesterol in the enterocytes is excreted back in the intestinal lumen as cholesteryl esters.
D
Eating food rich in fats may have several effects in our body. Which of the following dietary fatty acids is known for its health benefits in lowering serum triglycerides?
A. Palmitic acid
B. Oleic acid
C. Linoleic acid
D. Eicosapentaoic acid
D
Cells metabolize LDL via receptor mediated endocytosis. LDL receptors respond to specific apolipoproteins. The apoprotein with the highest affinity to LDL receptors is?
A. apoprotein B100
B. apoprotein CI
C. apoprotein CII
D. apoprotein E
A
What enzyme is very important in the cholesterol transport and which serves to transfer cholesterol from HDL to VLDL and LDL, which can be returned to the liver for endocytosis?
A. Lecithin:cholesterol acyltransferase (LCAT)
B. Cholesteryl ester transfer protein (CETP)
C. Lipoprotein lipase (LPL)
D. Acyl-coenzyme A:cholesterol acyltransferase (ACAT)
B
Which of the following statements best describe hormone sensitive lipase?
A. Hormone sensitive lipase breaks the C-H bonds found in fatty acids
B. Hormone sensitive lipase is located in the endothelial cells lining blood vessel walls
C. Hormone sensitive lipase is active in the phosphorylated form
D. Hormone sensitive lipase is activated by Insulin
C
Which of the following factors are associated with increased digestibility and absorption of dietary lipids?
a. High fat consumption
b. Older age of consumption
c. Longer fatty acid length
d. More saturated fat content
C
Which of the following is TRUE about essential fatty acids?
a. They can be synthesized by humans
b. They cannot be synthesized by plants
c. They do not maintain membranes
d. They have double bonds at delta12 and delta15
D
Which of the ff statements regarding Omega-3 is FALSE?
a. Synthesized in the human body
b. Linoleic acid can be synthesized de novo in the human body
d. Linoleic acid can be derived from the diet
b
Which of the following inhibits LPL?
a. A-II
b. C-I
c. C-II
d. C-III
D
Enzyme that digests lipids in the mouth
Lingual lipase
On which lipids does lingual lipase act on?
Short and medium chains
Enzyme that digests lipids in the stomach
Gastric lipase
On which lipids does gastric lipase act on?
Short and medium chains
Why are lingual lipases essential in neonates?
Lingual lipases are needed to digest the lipids found in milk, the only nutrition an infant can take in since birth to a few months
What is the importance of emulsification in the small intestines?
Emulsification increases the surface area of hydrophobic lipid droplets so that the digestive enzymes which work at the interface of the droplet and the surrounding aqueous solution can act effecticely
Which complementary mechanisms carry out emulsification?
Bile salts and peristalsys
Which organ secretes bile?
Liver
Bile salts are derived from which lipids?
Cholesterol
Which stimulates the gallbladder to contract in order to transfer bile salts into the small intestines?
CCK
What stimulates the secretion of CCK?
The entry of acidic gastric contents into the duodenum
The entry of acidic gastric contents into the duodenum stimulates the secretion of which substances?
CCK and bicarbonate
What is the function of bicarbonate?
Neutralizes the acid from the stomach and deactivates gastric lipase
Which stimulates the secretion of pancreatic lipase?
CCK
How many carbons do short and medium chains have?
12 and below
Bile salts convert dietary fats into lipid bilayers of bile salts and TAGs. T/F
F
It converts them into mixed micelles.
Pancreatic lipase converts TAGs to what substances?
2-Monoacylglycerides, free fa
Mixed micelles can diffuse into intestinal cells. T/F
T
Lipid-binding proteins in the blood, responsible for transport of TAGs, phospholipids, cholesterol, and cholesteryl esters between organs
Apolipoproteins
In lipoproteins, hydrophobic lipids are at the surface while hydrophilic protein side chains and lipid head groups are at the core. T/F
F
The hydrophobic lipids are at the core while the hydrophilic protein side chains and lipid head groups are at the surface
Arrange lipoproteins in ascending density
Chylomicrons, VLDL, IDL, LDL, HDL
Arrange lipoproteins in ascending size
HDL, LDL, IDL, VLDL, chylomicrons
Lipoprotein with most protein content
HDL
Lipoprotein with highest lipid content
Chylomicrons
Most of the lipid content of chylomicrons are what type?
TAG
Lipoprotein which contains most cholesterol
LDL
Lipoprotein containing most TAG
Chylomicrons
Unique apolipoprotein of chylomicrons
Apo B-48
Unique apolipoprotein of VLDL, LDL, IDL
Apo B-100
Which lipoprotein has no Apo B?
HDL
Which lipoprotein has Apo B-100?
VLDL, IDL, LDL
Which lipoprotein has Apo B-48?
Chylomicrons
The specific function of a lipoprotein is determined by which three factors?
Point of synthesis, lipid composition, apolipoprotein content
Where are chylomicrons synthesized?
In ER of epithelial enterocytes
Chylomicrons from the intestinal cells enter the blood stream through which vessel?
Left subclavian
Lipoprotein with lowest protein content
Chylomicrons
Lipoprotein with lowest TAG content
HDL
Lipoprotein with lowest cholesterol content
Chylomicrons
Major apoprotein of HDL
Apo A-I
Which apolipoprotein activates lipoprotein lipase?
Apo C-II
Which lipoproteins have Apo C-II?
Chylomicrons, VLDVL, HDL
Contents of chylomicron remnants
Cholesterol, Apo B-48, Apo E
Where is the chylomicron remnant absorbed?
Liver
Uptake of chylomicron remnants in the liver is through which cell mechanism?
Endocytosis
Where are VLDLs synthesized?
Hepatic cells
Which organ removes VLDV remnants in circulation?
Liver
IDL are VLDL remnants. T/F
T
When VLDL loses TAGs, to which is it converted?
IDL
When IDL from VLDL loses more TAGs, to which is it converted?
LDL
Where does HDL originate?
Hepatocytes and enterocytes
Which lipoprotein has no cholesteryl esters?
HDL
Which lipoprotein contais LCAT?
HDL
Function of LCAT
Catalyzes formulation of cholesteryl esters from lecithin (phosphatidylcholine) and cholesterol
Which lipoprotein transforms cholesterol and lecithin of VLDL and chylomicrons to cholesteryl esters and brings them to the liver?
HDL
A mature HDL is taken up by the liver by which mechanism?
Endocytosis
The most abundant component of chylomicrons is which of the following?
(A) ApoB-48 (B) Triglyceride (C) Phospholipid (D) Cholesterol (E) Cholesterol ester
B
The conversion of nascent chylomicrons to mature chylomicrons requires which of the following?
(A) Bile salts (B) 2-Monoacylglycerol (C) Lipoprotein lipase (D) High-density lipoprotein (E) Lymphatic system
D
The apoproteins B-48 and B-100 are similar with respect to which of the following?
(A) They are synthesized from the same gene.
(B) They are derived by alternative spicing of the same hnRNA.
(C) ApoB-48 is a proteolytic product of apoB-100.
(D) Both are found in mature chylomicrons.
(E) Both are found in very-low-density lipoproteins.
A
Bile salts must reach a particular concentration within the intestinal lumen before they are effective agents for lipid digestion. This is because of which of the following?
(A) The bile salt concentration must be equal to the triglyceride concentration.
(B) The bile salt solubility in the lumen is a critical factor.
(C) The ability of bile salts to bind lipase is concentration dependant.
(D) The bile salts cannot be reabsorbed in the ileum until they reach a certain concentration.
(E) The bile salts do not activate lipase until they reach a particular concentration.
D
Type III hyperlipidemia is caused by a deficiency of apoprotein E. Analysis of the serum of patients with this disorder would exhibit which of the following?
(A) An absence of chylomicrons after eating
(B) Above-normal levels of VLDL after eating
(C) Normal triglyceride levels
(D) Elevated triglyceride levels
(E) Below-normal triglyceride levels
B
Which one of the following statements about the
absorption of lipids from the intestine is correct?
A. Dietary triacylglycerol is partially hydrolyzed and absorbed as free fatty acids and monoacylglycerol.
B. Dietary triacylglycerol must be completely hydrolyzed to free fatty acids and glycerol before absorption.
C. Release of fatty acids from triacylglycerol in the intestine is inhibited by bile salts.
D. Fatty acids that contain ten carbons or less are absorbed and enter the circulation primarily via the lymphatic system.
E. Formation of chylomicrons does not require protein synthesis in the intestinal mucosa.
A
The form in which most dietary lipids are packaged and exported from the intestinal mucosal cells is as:
A. free fatty acids. B. mixed micelles. C. free triacylglycerol. D. 2-monoacylglycerol E. chylomicrons.
E
Where are LPLs located?
Walls of blood capillaries
LPL is anchored to the endothelium by which GAG?
Heparan sulfate
Unesterified fatty acids are transported in circulation using which molecule?
Serum albumin
A family of proteins that restrict access to lipid droplets stored in adipocytes to prevent untimely lipid mobilization
Perilipins
Which hormones activate the hormone-sensitive lipase?
Epinephrine and glucagon
Hormone-sensitive lipase is active when phosphorylated. T/F
T
Which protein phosphorylates hormone-sensitive lipase?
Perilipin A, and PKA
About 95% of the biologically available energy of TAG resides in their three long chin FA; only 5% is contributed by the glycerol moiety. T/F
T
FAs of 12 or fewer carbons enter the mitochondria without the help of membrane transporters. T/F
T
In the transport of FA into the mitochondria, what is the first reaction catalyzed?
Synthesis of fatty acid-CoA from FFA and CoA
Which enzyme catalyzes the reaction producing fatty aciy-COA to transport FA into the mitochonria?
Acyl-CoA synthetase
To what molecule must fatty acid be converted to in order to cross the mitochondrial membranes?
Fatty-acyl carnitine
Which enzyme converts fatty acids to fatty acyl-carnitine?
Carnitine acyltransferase I
Your mom read that PUFAs are good for your health.
You recommend the following, except
\A. corn
B. coconut
C. tuna
D. Salmon
B
Orlistat is a weight-reducing drug that reduces amount of fat absorbed by 30%. Which of the following lipase is affected?
A. lipoprotein lipase
B. pancreatic Lipase
C. Gastric Lipase
D. Hepatic Lipase
B
What is the role served by B-100 in relation to LDL and its receptor?
A. Part of the apolipoprotein structure
B. Cofactor for enzyme
C. Inhibitor of enzyme
D. Ligand for interaction
D
Whcih apolipoprotein is also known as the cholesteryl ester transfer protein (CETP), the protein which facilitates the exchange of triglycerides for cholesterol from VLDL
particles to HDL particles
A. Apo A-1
B. Apo C-1
C. Apo D
D. Apo E
D
Apolipoproteins are readily shuttled from triglyceride-
rich apolipoproteins to HDL and back again. Which of the
following apolipoproteins is not exchangeable?
A. Apo A-1
B. Apo C-1
C. Apo D
D. Apo E
C
Which of the following digestive enzymes is responsible for hydrolyzing triacylglycerols to form free fatty acids and monoacylgycerols? It is also the enzyme inhibited by the anti-obesity drug Orlistat.
A. Lingual lipase
B. Gastric lipase
C. Pancreatic lipase
D. Lipoprotein lipase
D
