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Semester 2-MEH > Session 4-Lipid Transport > Flashcards

Session 4-Lipid Transport Flashcards

1
Q

How is cholesterol transported in the blood?

A

As cholesterol esters

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2
Q

How are ~98% of lipids carried in the blood?

A

As lipoprotein particles consisting of phospholipid, cholesterol, cholesterol esters, proteins and TAG

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3
Q

True or false: micelles can transport hydrophobic cargo

A

TRUE

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4
Q

Where is most cholesterol synthesised?

A

In liver

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5
Q

Which steroid hormones is cholesterol a precursor of?

A

Cortisol
Aldosterone
Testosterone
Oestrogen

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6
Q

True or false: cholesterol is a precursor of bile acids

A

TRUE

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7
Q

Which enzymes catalyse the esterification of cholesterol to cholesterol ester?

A

Lecithin cholesterol acyltransferase (LCAT)

OR

Acyl-coenzyme A

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8
Q

What are the five distinct classes of lipoproteins?

A

1) chylomicrons
2) VLDL (very low density lipoproteins)
3) IDL (intermediate density lipoproteins)
4) LDL (low density lipoproteins)
5) HDL (high density lipoproteins)

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9
Q

What do the five classes of lipoproteins contain a variable content of?

A

Apolipoprotein
Triglyceride
Cholesterol
Cholesterol ester

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10
Q

Which classes of lipoproteins are the main carriers of TAGs?

A

Chylomicrons

VLDL

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11
Q

Which classes of lipoproteins are the main carriers of cholesterol esters?

A

IDL
LDL
HDL

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12
Q

Which lipoprotein is the most dense and what does this mean in terms of its protein content?

A

HDL - high % protein

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13
Q

What are apolipoproteins?

A

Each class of lipoprotein particle has a particular complement of associated proteins

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14
Q

What are the six major classes of apolipoproteins?

A 
A
B
C
D
E
H
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15
Q

Which classes of lipoprotein contain apoB?

A

VLDL
IDL
LDL

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16
Q

Which class of lipoprotein contains apoAI?

A

HDL

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17
Q

What are the two roles of apolipoproteins?

A

1) structural: packaging water insoluble lipid

2) functional: co-factor for enzymes to break down lipids and ligands for cell surface receptors

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18
Q

What is the difference between apoB-48 and apoB-100?

A

RNA editing-mRNA of apoB-48 gets premature stop codon 48% of the way down

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19
Q

Complete the sentences:

Chylomicrons are loaded in the ______ __________ and apoB-___ is added before entering the lymphatic system. Travel to thoracic duct which empties into _____ ___________ ______ and acquire 2 new apolipoproteins (apo__ and apo__) once in blood.

A 
Small intestine 
48
Left subclavian vein 
C
E
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20
Q

What does apoC bind to?

A

Lipoprotein lipase (LPL) on adipocytes and muscle

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21
Q

When does a chylomicron remnant form?

A

When triglyceride is reduced to ~20%, apoC dissociates and chylomicron becomes remnant

22
Q

Complete the sentences:

Chylomicron remnants return to the ______. LDL receptor on _____________ binds apo__ and chylomicron remnant is taken up by receptor mediated ________________. Lysosomes release remaining contents for use in _____________.

A 
Liver
Hepatocytes
E
Endocytosis 
Metabolism
23
Q

Which cofactor does lipoprotein lipase require to hydrolyse TAG in lipoproteins?

A

ApoC-II

24
Q

Where does lipoprotein lipase attach?

A

Surface of endothelial walls of capillaries of muscle and adipose

25
Q

What is the purpose of VLDL?

A

Transports TAG to other tissues

26
Q

Complete the flowchart:

VLDL -> _DL -> _DL

A

I

L

27
Q

What is the primary function of LDL?

A

Provide cholesterol from liver to peripheral tissues

28
Q

Why are LDLs not efficiently cleared by the liver?

A

Don’t have apoC or apoE

29
Q

Why is LDL more susceptible to oxidative damage?

A

Half life of LDL in blood is much longer than VLDL or IDL

30
Q

What can oxidised LDL taken up by macrophages transform into?

A

Foam cells and this contributes to the formation of atherosclerotic plaques

31
Q

Where is nascent HDL synthesised?

A

Liver and intestine

32
Q

Which apolipoprotein can acquire cholesterol and phospholipid from other lipoproteins to form nascent-like HDL?

A

ApoA-I

33
Q

True or false: transfer of lipids to HDL does not require enzyme activity

A

TRUE

34
Q

Which protein within the cell facilitates the transfer of cholesterol to HDL?

A

ABCA1

35
Q

By which receptor can cells requiring additional cholesterol obtain it from HDL?

A

Scavenger receptor (SR-B1)

36
Q

HDL can exchange cholesterol ester for TAG with VLDL via the action of which protein?

A

Cholesterol exchange transfer protein (CETP)

37
Q

What is the function of chylomicrons?

A

Transport dietary TAG from intestine to tissues such as adipose tissue

38
Q

What is the function of VLDL?

A

Transports TAG synthesised in liver to adipose tissue for storage

39
Q

What is the function of IDL?

A

Short-lived precursor of LDL, transport of cholesterol synthesised in liver to tissues

40
Q

What is the function of LDL?

A

Transport of cholesterol synthesised in liver to tissues

41
Q

What is the function of HDL?

A

Transport of excess cholesterol from cells to liver for disposal as bile salts and to cells requiring additional cholesterol

42
Q

What is hyperlipoproteinaemia?

A

Raised plasma level of one or more lipoprotein classes

43
Q

What can cause hyperlipoproteinaemia?

A

Over-production of lipoproteins

Under-removal

44
Q

What causes type I hyperlipoproteinaemia?

A

Chylomicrons in fasting plasma, caused by defective lipoprotein lipase

45
Q

What cases IIa hyperlipoproteinaemia?

A

Associated with coronary artery disease, caused by defective LDL receptor

46
Q

What causes type III hyperlipoproteinaemia?

A

Raised IDL and chylomicron remnants. Associated with coronary artery disease. Caused by defective apoE

47
Q

What are the clinical signs of hypercholesterolaemia?

A

1) xanthelasma - yellow patches on eyelids
2) tendon xanthoma - nodules on tendon
3) corneal arcus - white circle around eye

48
Q

How can raised serum LDL lead to angina?

A

1) oxidised LDL
2) recognised and engulfed by macrophages
3) lipid laden macrophages called foam cells accumulate in intima of blood vessels to form fatty streak
4) fatty streaks evolve into atherosclerotic plaque
5) encroaches on lumen of artery and can occlude coronary artery -> angina

49
Q

How can raised serum LDL lead to stroke or MI?

A

1) oxidised LDL
2) recognised and engulfed by macrophages
3) lipid laden macrophages called foam cells accumulate in intima of blood vessels to form fatty streak
4) fatty streaks evolve into atherosclerotic plaque
5) encroaches on lumen of artery
6) ruptures
7) thrombosis

50
Q

What is the first approach for treating hyperlipoproteinaemias?

A

Diet-reduce cholesterol and saturated lipids in duet and increase fibre

Lifestyle-increase exercise and stop smoking

51
Q

If the first approach to treating hyperlipoproteinaemias doesn’t work, which drugs can be used?

A

Statins-reduce cholesterol synthesis by inhibits HMG-CoA reductase

Bile salt sequestrants-bind bile salts in GI tract, forces liver to produce more build acids using more cholesterol

52
Q

What is the ideal concentration of total cholesterol in the blood?

A

5 mmol/L or less

Semester 2-MEH (21 decks)

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