Met 1: Lipoprotein

Question 1

Droplets of circulating fat are called _____, and they are required for transport because ____________.

Answer 1

Droplets of circulating fat are called lipoproteins, and they are required for transport because lipids are nonpolar.

Question 2

Compare the polarity of TG’s, free fatty acids, free cholesterol, phospholipids, and cholesterol ester

Answer 2

From most polar to least polar:

• Free fatty acids
• phospholipids
• free cholesterol
• cholesterol ester
• TG’s

Question 3

Which lipid can be transported in blood without lipoprotein?

Answer 3

Free fatty acids

Only lipid polar enough to dissolve in blood

Question 4

Compare the size of chylomicrons, LDL, HDL, IDL, and VLDL. How does this line up with % cholesterol ester and % triglyceride?

Answer 4

From biggest to smallest:

• Chylomicrons
• VLDL
• IDL
• LDL
• HDL

Biggest ones are mostly TG, smallest ones are mostly cholesterol ester.

Question 5

Describe the distribution of lipids in a lipoprotein

Answer 5

Inner core: cholesterol ester and TG’s

Outer shell: phospholipids and free cholesterol

Question 6

What apoproteins can be found on chylomicrons, IDL, VLDL, LDL, and HDL?

Answer 6

Chylomicrons: apoB48 (structural), apoC2, apoE

IDL: apoE

VLDL: apoB100, apoC2, apoE

LDL: apoB100

HDL: apoA1

Question 7

Describe the synthesis and delivery of chylomicrons

Answer 7

• Dietary fat gets absorbed in GI tract
• Enterocyte creates chylomicrons
• Chylomicrons travel through lacteal and eventually get into blood
• Chylomicrons are degraded by lipoprotein lipase in the vessel wall
• Skeletal muscle and adipose can then absorb the fats
• Remnant is IDL

Question 8

Describe the metabolism of lipoproteins at the vessel wall

Answer 8

• Chylomicrons and VLDL are degraded by lipoprotein lipase in vessel wall
  
  • Lipoprotein lipase recognizes apoC2 on the chylomicron & VLDL
• Freed fats can be absorbed by tissues
• The remnant lipoprotein from chylomicron is now an IDL
• The remnant lipoprotein from VLDL is now LDL

Question 9

How are IDL’s cleared from blood?

Answer 9

Liver recognizes apoE on IDL

Question 10

Describe the synthesis and delivery of VLDL

Answer 10

• Glucose is converted into lipids in the liver
• Liver makes VLDL
• VLDL travels into gets degraded at vessel wall by lipoprotein lipase
• fats get absorbed by adipose tissue and skeletal muscle
• remnant is LDL

Question 11

Compare the function of chylomicrons and VLDL

Answer 11

Chylomicrons are for absorption of dietary fat

VLDL is for delivery of fats from liver

Question 12

LDL is a byproduct of _______ metabolism by ____

IDL is a byproduct of ______ metabolism by ____

Answer 12

LDL is a byproduct of VLDL metabolism by lipoprotein lipase

IDL is a byproduct of chylomicron metabolism by lipoprotein lipase

Question 13

Atherosclerotic plaque is due to what lipoprotein?

Answer 13

Atherosclerotic plaque is due to LDL cholesterol esters

Question 14

What apoprotein is found on both VLDL and its remnant, LDL?

Answer 14

Apo-B100

Question 15

Describe the secretion and path of HDL

Answer 15

1. apoA1 is secreted from liver and GI tract
2. apoA1 picks up free cholesterol from atherosclerotic plaques
   
   • requires ABC-A1 enzyme
3. HDL traps free cholesterol inside by esterification
   
   • uses LCAT enzyme
4. HDL travels back to the liver