Lipid Digestion

Question 0

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

Answer 0

Endogenous and exogenous

Question 1

What are lipoproteins and what do they do?

Answer 1

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

Question 2

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

Answer 2

It is used to classify lipoproteins.

Difference in composition, structure, and function.

Question 3

Protein constituents of lipoproteins have what 2 roles?

Answer 3

structural and functional

Question 4

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

Answer 4

Spherical with proteins, cholesterol, and phospholipids on the surface

Question 5

What makes up the inside of the sphere?

Answer 5

Non-polar lipids

Question 6

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

Answer 6

Determined based upon density

Chylomicrons, VLDL, ILDL, LDL, HDL

Question 7

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

Answer 7

True

Question 8

Which Apoproteins are embedded in the monolayer?

Answer 8

Apo B100 and Apo B48

Question 9

What carries free fatty acids?

Answer 9

Albumin

Question 10

Which lipoprotein has the smallest density? Why?

Answer 10

Chylomicrons; they are filled with TAGs

Question 11

Which lipoproteins are the most dense? Why?

Answer 11

HDLs; they are full of esterfied cholesterol

Question 12

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

Answer 12

Chylomicrons are the largest; HDL is the smallest

Question 13

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

Answer 13

LDL

Question 14

What is the purpose of bile salts?

Answer 14

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

Question 15

What do intestinal enzymes breakdown?

Answer 15

Dietary TAG, cholesterol esters, and phospholipids

Question 16

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

Answer 16

Pancreatic lipase, Cholesterol esterase, and Phospholipase

Helper: Colipase

Question 17

What is the purpose of pancreatic lipase?

Answer 17

Cleaves ester bonds in dietary TAG

Question 18

What is the purpose of Colipase?

Answer 18

Helps pancreatic lipase attach to micelles.

Question 19

What is the purpose of Cholesterol esterase?

Answer 19

Hydrolyzes cholesterol esters

Question 20

What is the purpose of Phospholipases?

Answer 20

Breaks down phospholipids

Question 21

Where are TAGs and cholesterols transferred?

Answer 21

They are transferred across the intestinal mucosa

Question 22

What happens to TAGs and cholesterol once inside the enterocyte?

Answer 22

TAG: are reformed
Cholesterol: esterfied with fatty acids

Question 23

What is required to bring TAGs into the chylomicrons?

Answer 23

Microsomal Triglycerides Transferase

Question 24

Once formed, where are chylomicrons transferred and where to they go from there?

Answer 24

Lymphatic circulation then it goes to the blood stream (L Subclavian Vein)

Question 25

What enzyme in the blood stream is activated by Apo CII in the Chylomicrons and VLDs?

Answer 25

Lipoprotein lipase

Question 26

What does lipoprotein lipase do to the Chylomicrons?

Answer 26

They release fatty acids from the Chylomicrons

Question 27

What happens to the released fatty acids from the Chylomicrons?

Answer 27

They enter cells and are repackaged into VLDLs.

Question 28

What happens to Chylomicron remnants?

Answer 28

They are degraded by the liver.

Question 29

True/False: Chylomicrons release cholesterol to the tissues

Answer 29

FALSE!!! They DO NOT release cholesterol to tissues.

Question 30

Chylomicrons are carriers of lipids from what area?

Answer 30

The GI

Question 31

Where and when are chylomicrons synthesized?

Answer 31

intestinal epithelium; after a meal

Question 32

Of what are the chylomicrons the principal carriers?

Answer 32

dietary lipids and fat-soluable vitamins (D,A,K,E)

Question 33

What is the purpose of chylomicrons?

Answer 33

Deliver lipids to tissues.

Question 34

Where would you NOT find chylomicrons?

Answer 34

normal fasting plasma

Question 35

What apoproteins are in chylomicrons?

Answer 35

Apo B-48 (added upon formation) | A-I, C-II, E (added after entering the blood from HDL)

Question 36

Where and from what are VLDLs made?

Answer 36

Liver; biosynthesis of FA and chylomicron remnants.

Question 37

What is the main purpose of VLDLs?

Answer 37

They are the main carrier of endogenously synthesized TAGs to tissues

Question 38

Which apoproteins are in VLDLs?

Answer 38

Apo B-100 (Added upon synthesis) | C-II, and E (Added from HDL in the blood stream)

Question 39

Where and from what are LDLs formed? What is the intermediate structure?

Answer 39

They are formed from VLDLs in the circulation; ILDL

Question 40

What is the purpose of LDLs?

Answer 40

Transport cholesterol to the tissues

Question 41

Which Apoprotein is contained in LDL? How does that differ from ILDL?

Answer 41

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

Question 42

HDL is the smallest lipoprotein particle but most abundant, what is its function?

Answer 42

It takes cholesterol from the tissues back to the liver for excretion. It also distributes cholesterol to other lipoproteins (reverse cholesterol transport).

Question 43

Which apoproteins does HDL contain?

Answer 43

Apo A-I and A-II

Question 44

Where is HDL made?

Answer 44

Liver and sm. intestines

Question 45

What is the purpose of Apoprotein A-1?

Answer 45

Activates LCAT and binds HDL receptor | HelLcat esterfies

Question 46

What is the function of Apoprotein B-48?

Answer 46

It is involved in the formation of chylomicrons (embedded within the monolayer)

Question 47

What is the function of Apoprotein B-100?

Answer 47

It binds LDL receptor (docking element)

Question 48

What is the function of Apoprotein C-II? And which lipoproteins does this effect?

Answer 48

It activates lipoprotein lipase (LPL); chylomicrons and VLDLs

Question 49

What is the function of Apoprotein E?

Answer 49

Recognition of the LDL receptor (docking protein to remove the remnants of chylomicrons)

Question 50

What protein is involved in reverse cholesterol transport (aside from HDL)?

Answer 50

Cholesterol ester transfer protein (CETP) - it mediates the exchange of cholesterol from HDL to VLDL, ILDL, and LDL

Question 51

What is the function of lipoprotein lipase?

Answer 51

It delipidates VLDL and the chylomicrons at the capillary surface

Question 52

What is LCAT?

Answer 52

It is a peripheral protein that is made in the liver and secreted in the blood.

Question 53

What can happen to LDL in the presence of ROS?

Answer 53

It can not get rid of fat and produces fatty streaks in the coronary vessels, leading to plaque build-up.

Question 54

What is the shape of HDL prior to esterification by LCAT?

Answer 54

It begins as a disc, but as cholesterol esters are added, it becomes more dense and spherical.

Question 55

What type of receptor is an LDL receptor?

Answer 55

glycoprotein

Question 56

What is ACAT (aceyl-CoA cholesterol acyl transferase)?

Answer 56

It transfers a FA from fatty acyl CoA to cholesterol producing a cholesterol ester, which is then stored.

Question 57

What is another activator of lipoprotein lipase?

Answer 57

Insulin

Question 58

Once the chylomicron is deplipidated, which peripheral apoprotein is returned to HDL? And what is the function of the remaining peripheral apoprotein?

Answer 58

Apo C-II is returned to HDL. Apo E remains to bind to receptors on the liver for endocytosis.