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Metabolism > Lipid Transport > Flashcards

Lipid Transport Flashcards

0
Q

Smallest methods of lipid transport is?

A

Bound to Albumin by non-covalent bonds
On 2% of lipids transported, mostly FA. -3mmol/L
Albumin produced in liver, high levels indicate high protein diet or dehydration, low indicates kidney-liver damage

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1
Q

Why is it hard to transport lipids on their own?

A

Lipids are hyrodphobic hence must be carried

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2
Q

Largest method of lipid transport?

A

Lipoproteins particles in the plasma.

Transports 98% of lipids.

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3
Q

What are Micelles?

A

Polar molecules of proteins and phospholipids with cholesterol for stability.
They are APOLIPOPROTEIN composition

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4
Q

What do lipoproteins transport?

A 
Triacylglycerides
Cholesterol esters (transport form)
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5
Q

How big are the lipoproteins?

A

5-100 nm

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6
Q

How do lipoproteins vary?

A

Density
Surface
Function

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7
Q

Describe the different classes of lipoproteins?

A 
Each class has own lipoproteins A-H
Determined by enzyme activation from recognition on cell surface receptors or POLYMORPHISM esp ApoE because different phenotype so exist hence different expression.
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8
Q

Characteristics of APOLIPOPROTEIN?

A

Packages non-water soluble lipids in a hydrophilic case.

Contains hydrophobic and hydrophilic

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9
Q

What Chylomicrons?

A

The least dense Apoproteins + TAGs to transport lipids. Released from intestine endothelium of blood vessels, transported via lymphatic system to cells.
This gives the lymphatic vessels a white appearance after a fatty diet.

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10
Q

What are Very low density lipoproteins?

VLDLs

A

2nd least dense lipoproteins.
Formed by liver to store energy.
TAGS+ specific apoproteins to carry lipids from liver to tissue

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11
Q

What are LDLs?

Low density lipoproteins?

A

Cholesterol rich and contains specific Apoprotiens (Apo B100)
Formed in liver
2nd MOST dense
The more LDLs, the higher the risk of atherscelorisis

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12
Q

What are HDLs?

A

The most dense lipoproteins.
Formed by tissue.
Carries excess cholesterol from tissue and arteries to liver where disposed at bile salts.

HDL>LDL is good!

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13
Q

What are NASCENT HDLs?

A

Some HDLs synthesised as shells by liver/from vLDL remnants.

They pick up cholesterol from capillaries then mature into HDLs and take back to liver

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14
Q

What are the characteristics of lipoproteins?

A

Their surface coat is comprised of phospholipids, cholesterol and apoproteins

Sphere shape provides stability
The ratio of core to surface lipids ensures stability. Removal of core lipids meNd the surface must shrink.

Can only remove the core lipids using enzymes, eg lipase, transferase proteins.

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15
Q

Explain how the tissue obtain the lipids they require FOR the lipoproteins?

A

Lipase on plasma membrane of endothelium of capillaries.
Chylomicron bonds to vLDLs.
Cleaves TAGs into Glycerol and FA by hydrolysis.
Gylerol is in circulation.
FA goes into tissues for metabolism
vLDL remnants (chylomicrons) removed by liver and converted into other lipoproteins

16
Q

What is Receptor-mediated Enocytosis?

A

Cholesterol transfer using LDLs
- cells have LDL receptors.
LDL containing cholesterol esters binds to the ApoB-100 receptors causing the cell to wrap around the lipoprotein
The complex then separates into a membrane of receptors which returns back on to the plasma membrane, and a sphere of the lipoprotein.
Lysosomes digests the cholesterol esters to release the FA & free cholesterol

17
Q

How is LDL receptor expression regulated?

A

By cholesterol uptake.
If cholesterol is taken up, synthesis is inhibited in cell.
Hence less LDL receptors leads to excess cholesterol.

18
Q

Biosynthsis vs uptake: cholesterol?

A

Cells can biosynthesise cholesterol from Acetyl-CoA, but prefer uptake of PRE-FOREMD cholesterol from blood

19
Q

What is HYPERLIPOPROTEINAEMIAS?

A

Raised levels of 1 or more classes of lipoproteins

Due to over-production or under-removal.

20
Q

Why might there be a defect?

A

Enzymes
Receptors
Apoproteins

21
Q

What diseases is Hyperlipoproteinaemias linked to?

A

Atherosclerosis and Coronary Artery Disease.

This occurs with high LDLs and cholesterol in blood.

22
Q

What diseases can Hyperlipoproteineamias cause?

A

Xanthelasma

&

Corneal Arcus

23
Q

What is Xanthelasma?

A

Cholesterol deposits in skin.

Can also occur in tendons and joints.

24
Q

What is Corneal Arcus?

A

A blue/grey ring in the corneal region of the eye.

25
Q

How can Hyperlipoproteinaemias be familial?

A

Abscence of homozygous (early) /deficiency of heterozygous (later onset) allele for functional LDL receptors.
LDLs binds to site of damaged artery causing atherosclerosis.

26
Q

What is Type 1?

A

Chylomicrons in fasting plasma, no CAD.

Defective lipoprotein lipase

27
Q

Type 2a?

A

Raised LDL levels
CHD
Defective LDL receptors

28
Q

Type 2b?

A

Raised LDL&vLDL levels

CHD

29
Q

Type 3?

A

Raised LDL and Chylomicrons reminants

CAD

30
Q

Type 4

A

Raised vLDL

CAD

31
Q

Type 5?

A

Raised Chylomicrons and vLDL in blood plasma

CAD

32
Q

Tx for Hyperlipoproteinaemias?

A

Drugs
- statins such as Simvastatin
Reduces cholesterol synthseis by inhibition of HMG CoA Reductase
Increased expression of LDL receptors in liver also increasing lipase conc.

33
Q

What are the side effects of statins eg Simvastatin?

A

Interference of important products such as
-Decreasing conc of Co-Enzyme Q10
Required for elctron shuttle in ETC
Hence causes muscle pain MYALGIA

Statin Myopathy
- Antibodies, that are anti-HMG CoA Reductase, destroying skeletal muscle

Metabolism (8 decks)

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