Lipid Transport Flashcards

1
Q

What are the 5 types of lipids?

A
  • Triacylglycrerol
  • Fatty acids
  • Cholesterol
  • Phospholipids
  • Vitamins (A, D, E and K)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe cholesterols

A
  • synthesised in the liver
  • essential for regulating membrane fluidity
  • precursor of steroid hormones and bile acids
  • transported as cholesterol ester
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are lipoproteins?

A

Biochemical assemblies of lipids and proteins to transport the lipid portion in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the five classes of lipoproteins?

A
  • Chylomicrons
  • VLDL (very low density lipoproteins)
  • IDL (intermediate density lipoproteins)
  • LDL (low density lipoproteins)
  • HDL (high density lipoproteins)

each contains variable content of apolipoproteins, TAG, cholesterol and cholesterol esters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are apolipoproteins?

A

Proteins that bind to lipids to package them into soluble particles (lipoproteins)
-apoB (VLDL, IDL, LDL) and apoA1 (HDL) are the most important

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe how chylomicrons come about

A

1) Dietary lipids absorbed in the intestine (hydrolysed first to fatty acids and glycerol)
2) Re-esterification to triacylglycerols and packaged into chylomicrons
3) apoB-48 added before entering lymphatic system
4) Enters the bloodstream which empties into left subclavian vein and gains 2 new apoproteins (C+E)
5) In the capillary walls of the target tissue (muscle and adipose), lipoprotein lipase hydrolyses them to release fatty acids (apoC binding)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens to the remainder of chylomicros (chylomicron remnants)?

A

1) When chylomicrons release their fatty acids to target tissues (by lipoprotein lipase), apoC dissociates when TAG reduced to ~20%
2) Chylomicron remnant goes to the liver, apoE and chymicron taken up via receptor mediated endocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is VLDL made?

A

Liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the purpose of VLDL?

A

transporting triacylglycerol to other tissues from the liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Which apolipoprotein is added during the formation of VLDL

A

apoB100 (apoC+E added later from HDL)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does VLDL release its contents to target tissues?

A

Binds to lipoprotein lipase on endothelial cells in muscle and adipose (same as chylomicrons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are IDLs formed?

A

when VLDL content further depletes to ~30% than returning to the liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How are LDLs formed?

A

Further depletion of IDLs to ~10% and apoC and apoE are lost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the purpose of LDL?

A

provide cholesterol from the liver to preipheral tissues (that have LDL receptors in them to be taken up by endocytosis)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the clinical relevance of LDLs?

A
  • LDLs have a longer half life (than VLDL or IDL) this makes them more suceptuble to oxidative damage
  • oxidised LDLs are phagocytosed by macrophages which ultimately leads to atherosclerotic plaques
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Briefly describe the process of Atherosclerosis

A

1) Oxidised LDL phagocytosed = foam cells
2) Foam cells acumulate in the intima = fatty streaks
3) Fatty streaks evolve to atherosclerotic plaques
4) Growth of plaques lead to angina
5) Further growth leads to ruptured vessels activating acute thrombosis = stroke or myocardial infarction

17
Q

Where are nascent (empty) HDLs synthesised?

18
Q

What is the function of HDLs?

A

Transport excess cholesterols from cells back to the liver or steroidogenic cells to give cholesterol to form steroid hormones

  • can take TAGs from LDLs
  • prevent foam cells forming
19
Q

What is hyperlipoproteinaemia?

A

Raised plasma level of one or more lipoprotein classes

-overproduction or under removal

20
Q

What is hypercholesterolaemia?

A

High level of cholesterol in the blood

21
Q

What is Xanthelasma?

A

Yellow patches on the eyelids (cholesterol deposits)

22
Q

What is tendon Xanthoma?

A

Nodules on tendons (cholesterol deposits)

23
Q

What is corneal arcus?

A

White circle around the iris of the eye (cholesterol deposits)

24
Q

How is hyperlipoproteinaemia treated?

A
  • Diet
  • Lifestyle
  • Drugs (statins or bile salt sequestrants)
25
Describe the mechanism of statins
Inhibits HMG-CoA reductase | -an enzyme in cholesterol synthesis
26
Describe the mechanism of bile salt sequestrants
They bind bile salts in the GI tract which forces liver to produce more bile acids thus using more cholesterol