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?

A

Liver

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
Q

Describe the mechanism of statins

A

Inhibits HMG-CoA reductase

-an enzyme in cholesterol synthesis

26
Q

Describe the mechanism of bile salt sequestrants

A

They bind bile salts in the GI tract which forces liver to produce more bile acids thus using more cholesterol