2.4 Lipoproteins and Lipid transport Flashcards

1
Q

What happens to a chylomicron once its secreted from the mucosal cells?

A

the chylomicrons circulate through the lymphatic system until it reaches the superior vena cava. During their time in the lymph and continuing in their plasma, chylomicrons undergo a number of physical-chemical and metabolic changes:

1) Gain apoC-II: Activates lipoprotein lipase. Which intitiates core triacylglycerol hydrolysis.
- triacylglycerol is mostly released to adipose, muscle, heart.
- Glycerol will be recycled to liver
- Apo E has receptors in the liver and the remaining chylomicron remnant will be degraded.

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2
Q

Chylomicron is essentially…….???

A

a fat droplet with triglycerols making up about 90% of its weight.

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3
Q

While chylomicron is getting transferred to its desired location, what else is happening? (regards to lipoproteins)

A

a number of other lipoproteins are formed to facilitate transport through the aqueous blood system.

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4
Q

Lipoprotein lipase?

A

breaks down TAGS to fatty acids and glycerol

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5
Q

What’s chylomicron half-life in plasma?

A

less than a hour.

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6
Q

How is chylomicrons triacylglcerol distributed?

A

80% Fatty acid: adipose, muscle, heart

20% Glycerol: recycled in liver.

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7
Q

What happens when fatty acids enter the tissue?

A

They get trapped in cells by conversion to fatty acyl-coA thioesters

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8
Q

What’s the enzyme used to convert fatty acids into fatty acyl-coA thioesters in cells?

A

fatty acyl-coA synthetase.

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9
Q

What is a chylomicron remnant?

A

it’s the “shrunken” lipoprotein…. Whatever is left of the chylomicron after Triacylglycerol is released via fatty acid and glycerol.

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10
Q

What happens to the chylomicron remnant?

A

The liver has receptors specific to APO E, which will take in the chylomicron remnant and gets degraded and recycled

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11
Q

Apo C II and Apo E?

A

They are picked up from HDL into chylomicrons.
Apo C II + lipoprotein lipase: converts TAG to fatty acid and glycerol.

Apo E: liver has receptor that recognizes it and will degrade chylomicron remnants.

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12
Q

Chylomicron: (composition)

A
  • Largest
  • lowers in density due to high lipid/protein ratio
  • highest in triacylglycerols as % of weight
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13
Q

VLDL (composition)

A
  • Very low density lipoprotein

- 2nd highest in triacylglycerols as % of weight

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14
Q

IDL (composition)

A

intermediate density lipoprotein

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15
Q

LDL (composition)

A

low density lipoprotein

highest in cholesterol/cholesteryl esters as % of weight

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16
Q

HDL (composition)

A

High density lipoprotein, highest in density due to high protein/lipid ratio