Lipid Digestion Flashcards

(59 cards)

0
Q

What are the two interconnected cycles of lipoprotein metabolism centered on the liver?

A

Endogenous and exogenous

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1
Q

What are lipoproteins and what do they do?

A

Non-covalent complexes of lipids and proteins; carry lipids through the bloodstream

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2
Q

What is purpose of particle density? What are the defining characteristics?

A

It is used to classify lipoproteins.

Difference in composition, structure, and function.

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3
Q

Protein constituents of lipoproteins have what 2 roles?

A

structural and functional

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4
Q

What is the shape of lipoproteins and what structures are on the surface?

A

Spherical with proteins, cholesterol, and phospholipids on the surface

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5
Q

What makes up the inside of the sphere?

A

Non-polar lipids

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6
Q

What are the major classifications of lipoproteins, and how are they determined?

A

Determined based upon density

Chylomicrons, VLDL, ILDL, LDL, HDL

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7
Q

True/False: The lipoproteins have a MONO-layer of mainly amphipathic lipids

A

True

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8
Q

Which Apoproteins are embedded in the monolayer?

A

Apo B100 and Apo B48

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9
Q

What carries free fatty acids?

A

Albumin

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10
Q

Which lipoprotein has the smallest density? Why?

A

Chylomicrons; they are filled with TAGs

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11
Q

Which lipoproteins are the most dense? Why?

A

HDLs; they are full of esterfied cholesterol

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12
Q

Which lipoproteins are the largest in diameter? Which are the smallest?

A

Chylomicrons are the largest; HDL is the smallest

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13
Q

Which lipoprotein has the highest percent of cholesterol and cholesterol ester?

A

LDL

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14
Q

What is the purpose of bile salts?

A

They emulsify dietary fats and increase surface area of the lipid to speed up digestion.

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15
Q

What do intestinal enzymes breakdown?

A

Dietary TAG, cholesterol esters, and phospholipids

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16
Q

What are the 3 main intestinal enzymes for digestion of lipids and what is the 1 helper enzyme?

A

Pancreatic lipase, Cholesterol esterase, and Phospholipase

Helper: Colipase

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17
Q

What is the purpose of pancreatic lipase?

A

Cleaves ester bonds in dietary TAG

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18
Q

What is the purpose of Colipase?

A

Helps pancreatic lipase attach to micelles.

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19
Q

What is the purpose of Cholesterol esterase?

A

Hydrolyzes cholesterol esters

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20
Q

What is the purpose of Phospholipases?

A

Breaks down phospholipids

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21
Q

Where are TAGs and cholesterols transferred?

A

They are transferred across the intestinal mucosa

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22
Q

What happens to TAGs and cholesterol once inside the enterocyte?

A

TAG: are reformed
Cholesterol: esterfied with fatty acids

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23
Q

What is required to bring TAGs into the chylomicrons?

A

Microsomal Triglycerides Transferase

24
Once formed, where are chylomicrons transferred and where to they go from there?
Lymphatic circulation then it goes to the blood stream (L Subclavian Vein)
25
What enzyme in the blood stream is activated by Apo CII in the Chylomicrons and VLDs?
Lipoprotein lipase
26
What does lipoprotein lipase do to the Chylomicrons?
They release fatty acids from the Chylomicrons
27
What happens to the released fatty acids from the Chylomicrons?
They enter cells and are repackaged into VLDLs.
28
What happens to Chylomicron remnants?
They are degraded by the liver.
29
True/False: Chylomicrons release cholesterol to the tissues
FALSE!!! They DO NOT release cholesterol to tissues.
30
Chylomicrons are carriers of lipids from what area?
The GI
31
Where and when are chylomicrons synthesized?
intestinal epithelium; after a meal
32
Of what are the chylomicrons the principal carriers?
dietary lipids and fat-soluable vitamins (D,A,K,E)
33
What is the purpose of chylomicrons?
Deliver lipids to tissues.
34
Where would you NOT find chylomicrons?
normal fasting plasma
35
What apoproteins are in chylomicrons?
Apo B-48 (added upon formation) | A-I, C-II, E (added after entering the blood from HDL)
36
Where and from what are VLDLs made?
Liver; biosynthesis of FA and chylomicron remnants.
37
What is the main purpose of VLDLs?
They are the main carrier of endogenously synthesized TAGs to tissues
38
Which apoproteins are in VLDLs?
Apo B-100 (Added upon synthesis) | C-II, and E (Added from HDL in the blood stream)
39
Where and from what are LDLs formed? What is the intermediate structure?
They are formed from VLDLs in the circulation; ILDL
40
What is the purpose of LDLs?
Transport cholesterol to the tissues
41
Which Apoprotein is contained in LDL? How does that differ from ILDL?
ILDL has Apo B-100, C-II, and E, but returns the Apo C-II and Apo E to HDL. It is then LDL and only contains Apo B-100
42
HDL is the smallest lipoprotein particle but most abundant, what is its function?
It takes cholesterol from the tissues back to the liver for excretion. It also distributes cholesterol to other lipoproteins (reverse cholesterol transport).
43
Which apoproteins does HDL contain?
Apo A-I and A-II
44
Where is HDL made?
Liver and sm. intestines
45
What is the purpose of Apoprotein A-1?
Activates LCAT and binds HDL receptor | HelLcat esterfies
46
What is the function of Apoprotein B-48?
It is involved in the formation of chylomicrons (embedded within the monolayer)
47
What is the function of Apoprotein B-100?
It binds LDL receptor (docking element)
48
What is the function of Apoprotein C-II? And which lipoproteins does this effect?
It activates lipoprotein lipase (LPL); chylomicrons and VLDLs
49
What is the function of Apoprotein E?
Recognition of the LDL receptor (docking protein to remove the remnants of chylomicrons)
50
What protein is involved in reverse cholesterol transport (aside from HDL)?
Cholesterol ester transfer protein (CETP) - it mediates the exchange of cholesterol from HDL to VLDL, ILDL, and LDL
51
What is the function of lipoprotein lipase?
It delipidates VLDL and the chylomicrons at the capillary surface
52
What is LCAT?
It is a peripheral protein that is made in the liver and secreted in the blood.
53
What can happen to LDL in the presence of ROS?
It can not get rid of fat and produces fatty streaks in the coronary vessels, leading to plaque build-up.
54
What is the shape of HDL prior to esterification by LCAT?
It begins as a disc, but as cholesterol esters are added, it becomes more dense and spherical.
55
What type of receptor is an LDL receptor?
glycoprotein
56
What is ACAT (aceyl-CoA cholesterol acyl transferase)?
It transfers a FA from fatty acyl CoA to cholesterol producing a cholesterol ester, which is then stored.
57
What is another activator of lipoprotein lipase?
Insulin
58
Once the chylomicron is deplipidated, which peripheral apoprotein is returned to HDL? And what is the function of the remaining peripheral apoprotein?
Apo C-II is returned to HDL. Apo E remains to bind to receptors on the liver for endocytosis.