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Biochemistry > Lipid Transport > Flashcards

Lipid Transport Flashcards

1
Q

What lipids are present in blood plasma?

A

Lipoproteins are most abundant

Fatty Acids

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2
Q

What is blood plasma?

A

All of the blood minus the cells

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3
Q

Blood serum is ________.

A

Blood plasma without clotting factors

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4
Q

What is used to transport lipids?

A

Lipoproteins

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5
Q

What is a lipoprotein?

A

A triglyceride, cholesterol, cholesterol ester, phospholipids form NON-COVALENT aggregates with proteins forming a complex known as lipoproteins

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6
Q

Hydrophobic lipids form the _____ of the lipoprotein

A

Core

Triglycerides
Cholesterol Esters

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7
Q

Amphipathic Lipids are a at the _______-

A

interface between aqueous medium and hydrophobic core

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8
Q

Apoproteins are _______.

A

Amphipathic

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9
Q

Chylomicrons and VLDL contain a high amount of _________.

What is the difference?

A

Triacylglycerols

Triacylgycerols carried by chylomicrons are obtained from the diet.

VLDLs carry triacylglycerols synthesized in the liver.

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10
Q

HDL has a lot of ________.

A

Proteins

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11
Q

Order the major human plasma lipoproteins from least dense to most.

A

Chylomicron
VLDL
IDL
LDL
HDL- LOTS of proteins

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12
Q

What makes up over 50% of lipids in LDL ?

A

Cholesterol and cholesterol esters

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13
Q

Where are the following produced?

Chylomicrons
VLDL
IDL
LDL
HDL

A

Chylomicrons - Intestinal epithelial cells from dietary fats

VLDL- Liver from dietary carbs

IDL- Blood

LDL- Blood

HDL- Liver and Intestine

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14
Q

What are the functions of the following?

Chylomicrons
VLDL
IDL
LDL
HDL

A

Chylomicrons - Carries TG in blood
VLDL - Carries TG in blood
IDL - Endocytosed by liver or converted to LDL
LDL- Endocytosed by liver and peripheral tissues
HDL- Returns cholesterol from peripheral tissues to liver, exchanges proteins and lipids with other lipoproteins

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15
Q

Which two lipoproteins carry lipids in blood?

A

Chylomicron

VLDL

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16
Q

Which is the only lipoprotein that returns cholesterol from tissues to the liver ?

What is one other function of this lipoprotein?

A

HDL

Exchanges proteins and lipids with other lipoproteins

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17
Q

Apoproteins are ________.

A

Proteins associated with lipoproteins.

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18
Q

Which apoprotein is the ligand for the LDL receptor?

A

B100 and E

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19
Q

What is the activator of LCAT?

A

Apoprotein A-1

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20
Q

What is the activator of lipoprotein lipase?

A

Apoprotein C-II

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21
Q

What is a chylomicron remnant receptor and also a ________ for LDL?

A

Ligand

Apoprotein E

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22
Q

What are the 4 enzymes involved in lipoprotein metabolism?

A
  1. Lipoprotein Lipase (LPL)
  2. Hepatic Lipase
  3. Lecithin-Cholesterol Acyltransferase(LCAT)
  4. AcylCoA :Cholesterol Acyltransferase (ACAT)
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23
Q

What is the function of LPL?

A

Processing of chylomicrons and VLDL

MOST IMPORTANT

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24
Q

What is the function of hepatic lipase?

What is another name?

A

Hepatic triglyceride lipase

IDL to LDL

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25
Q

What is the function of LCAT

A

Catalyze transfer of LCFA to cholesterol to make cholesterol esters

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26
Q

What is the function of ACAT?

A

Intracellular enzyme that makes cholesterol esters

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27
Q

Describe the formation of chylomicrons

A
  1. FA and 2MG are incorporated into micelles with the help of bile salts.
  2. Micelles enter epithelial cells of the intestine and regenerate TGs from FA and 2MG on the surface of SER
  3. TG combine with apoproteins from RER and phospholipids to migrate to the Golgi Body
  4. The Golgi pinches off vesciles to make chylomicrons and then exit into the lymph and then into the blood via exocytosis.
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28
Q

__________ breaks down triacylglycerols (TAGs) so that bile salts can __________

A

Pancreatic lipase breaks down triacylglycerols (TAGs) so that bile salts can incorporate them into micelles

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29
Q

Triacylglycerols are resynthesized by _________ in __________ using ______ and _______.

A

SER
Intestinal Epithelial Cells
FA and 2-monoglycerol

30
Q

Chylomicrons start as _____________ and end as ________.

A

Mixed Micelles, Nascent Chylomicrons

31
Q

When nascent chylomicrons enter the blood they will encounter ________ which will donate _____ and ______ which _____________.

A

HDL

Apoprotein E and CII which make the chylomicrons mature and become very large

32
Q

What tissues are related to LPL (lipoprotein lipase)?

A

Muscle and Adipose Tissue

These secrete LPL into the capillary tubes of the blood vessels. It is not incorporated fully into the blood.

33
Q

What does LPL do?

A

Once the Chylomicron TG has been matured by HDL donated Apoprotein E and CII, LPL will hydrolyze TAGs in chylomicrons to produce FATTY ACIDS AND GLYCEROL.

34
Q

The lack of Apoprotein CII will inhibit _______.

A

LPL activation.

35
Q

What are the products of lipoprotein lipase on mature Chylomicron TAG?

A

Create Fatty Acid and Glycerol

36
Q

Chylomicrons ________ in size by 50% after LPL activity and are called _______.

These bind to receptors on ______ and enter through ________. ______ enzyme degrades __________ to generate _______.

A

reduce

Remnants

Plasma membrane of liver and other cells and enter through endocytosis. Lysosomal enzyme degrades chylomicron remnants to generate

FA
Cholesterol
AA
Glycerol

37
Q

Chylomicrons are produced in ______ cells and end up in ________.

A

Intestinal Epithelial Cells

Liver Cells or other cells

38
Q

How is VLDL made?

A

Protein synthesized on the rough endoplasmic reticulum are packaged with triacylglycerol in the ER and Golgi complex to form VLDL.

VLDL are transported to the cell membrane in secretary vesicles, and secreted by exocytosis.

39
Q

VLDL is synthesized in the _______ and transported to the ________. It is in an __________. _______ transfers ______________ to make VLDL ________.

A

Liver, Blood

Immature state

HDL, Apoprotein E, CII, CE (Cholesterol Esters)

Mature

40
Q

What degrades TAGs in VLDL?

A

Lipoprotein Lipase

41
Q

IDL is produced in the ________. What is its precursor?

A

Blood

VLDL

42
Q

What is the difference between LPL and HTGL?

A

LPL is produced by muscle & adipose tissue and deals with larger particles such VLDL and Chylomicrons

HTGL is produced by liver tissue and deals with small particles such as IDL

43
Q

HTGL can hydrolyze _______ to ________.

A

IDL TG to Fatty acid and Glycerol

OR

LDL

44
Q

LDL is produced in the _____

A

blood

45
Q

IDL and LDL will get take up by _______.

A

Liver and Peripheral Cells

46
Q

What is the similarity between LPL and HTGL/

A

They both hydrolyze TGs to fatty acids and glycerols.

47
Q

VLDL when hydrolyzed by ______ is the precursor of _______ which is the precursor of ________ when hydrodlyzed by _____.

A

LPL , IDL

LDL, HTGL

48
Q

LDL consists of lots of cholesterols and ________.

Why is this bad for us?

A

Cholesterol esters

Humans do not have the enzymes to change the heterocyclic ring structure of cholesterol.

49
Q

Cholesterol esters can be ________ creating ________.

A

oxidized

oxidized LDL

50
Q

What does oxidized LDL do?

A

Cause damage to endothelial layer of blood vessel.

Macrophages will come to the site of injury and take out oxidized LDL without much regulation and form FOAM cells due to the buildup of LDL within themselves.

These foam cells form fatty streaks and eventually cause further endothelial damage.

Damaged endothelial cells release TXA2 and now macrophages and platelets will release growth factors.

These growth factors will cause proliferation and migration of smooth muscle cells to the intimal layer of arterial wall

Fibrous material will also create a thick collagen cap.

FOAM cells are believed to be the starting point for atherosclerosis.

51
Q

LPL from _______ cells is stimulated by _________.

A

Adipose Cells

Apoprotein CII and Insulin

52
Q

As long as either Apoprotein CII OR Insulin are available, LPL will function.

True or False

A

FALSE

Insulin must be available!

53
Q

Diabetic patients who have trouble controlling insulin may have a build up of ___________ because _________.

A

Chylomicrons and VLDL

LPL

54
Q

Hyperchylomicronemia

Treatment

A

Familial LPL or Apoprotein CII deficiency resulting in

Increased chylomicrons, VLDL, TGs and cholesterol in blood

Fat restriction

55
Q

Describe how the LDL Receptor works

Location

A

Surface of ER

LDL protein is synthesized and transported to Golgi Body via lipid vesicles and then to the plasma membrane.

These receptors must aggregate in order for LDL to bind and initiate endocytosis.

The receptor will bring in the LDL via a lipid vesicle which will get broken down by Lysosomes.

The receptor can be recycled

56
Q

LDL receptor is only on the liver cells.

True or False

A

FALSE

57
Q

LDL-receptor binds LDL only.

True or False

A

FALSE

LDL
VLDL
IDL
Chylomicron remnants
IDL

58
Q

A problem in LDL receptor will cause ________.

A

An accumulation of LDL in the blood

59
Q

Cholesterol regulates what enzyme?

A

HMG-CoA Reductase

60
Q

What can the cell do if cholesterol gets too high in cell?

A
  1. Insert cholesterol into plasma membrane
  2. Reduce HMG COoA reductase
  3. Use ACAT to convert cholesterol to cholesterol ester
  4. Reduce LDL receptors
61
Q

ACAT is located _______ the _____cell.

A

inside the liver

62
Q

HDL is produced by the _____.

A

Liver

63
Q

HDL becomes mature by _______.

A

Donating Apoproteins to VLDLs and chylomicrons

This makes HDL change shape from disc to spherical

64
Q

Mature HDL can pick up ________ from _____ using a protein called ______.

Cholesterol in peripheral tissues is now moved to the surface of HDL

______ in HDL will convert _________ to ______.

In the blood, _______ from VLDL will migrate to _____ while the _________ from HDL will migrate to _____.

A

cholesterol from peripheral tissue, ABC1

LCAT in HDL will convert cholesterol to cholesterol esters.

In the blood, TAGs from VLDL will migrate to HDL while the Cholesterol Ester from HDL will migrate to VLDL.

VLDL can be metabolized to IDL and then LDL which can be taken up by LDL receptors in the liver

65
Q

Liver is the only place we can synthesize cholesterol because _________.

A

It can produce bile salts

66
Q

What is reverse cholesterol transport?

A

The transfer of TG from VLDL to HDL and the Cholesterol Ester from HDL to VLDL

67
Q

LCAT converts _______ to _______.

A

Cholesterol to cholesterol esters

68
Q

LCAT is in the ______ and associated with ____.

A

Blood, HDL

69
Q

What is the best level of cholesterol?

A

Less than 200mg/dL

70
Q

How does Statin inhibit cholesterol synthesis?

A

Inhibit HMG CoA reductase

Cell will respond by increasing LDL receptors thus reducing blood cholesterol

71
Q

What is cholestyramine?

A

A drug that binds to bile salts making them unabsorabable by human bodies and thus being excreted through feces

Biochemistry (18 decks)

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