Dirty Medicine: Lipid Transport Part 3

Overview

• Final part of the lipid transport series.
• Builds on the first two videos: Chylomicron pathway into the liver.
• Focus: Lipoproteins and their pathway post-chylomicron remnant stage.

Key Concepts

Previous Video Recap

• Chylomicron moves from intestine to lymph, then systemic circulation.
• HDL supplies chylomicron with Apo C2 and Apo E.
• Chylomicron remnant enters the liver.

Lipoproteins

• VLDL (Very Low Density Lipoprotein):

  • Secreted by the liver.
  • Contains triglycerides and cholesterol.
  • Contains Apo B100 on its shell.
  • HDL loads VLDL with Apo E and Apo C2.

• IDL (Intermediate Density Lipoprotein):

  • VLDL converts to IDL.
  • Retains Apo E and Apo B100.
  • Can enter liver or convert to LDL.

• LDL (Low Density Lipoprotein):

  • Known as "bad cholesterol/fat."
  • Can be derived from IDL or secreted by the liver.
  • Carries Apo B100, which mediates LDL's entry into peripheral cells via LDL receptors.

High-Yield Concepts and Mnemonics

• Apo B100:

  • Function: Mediates endocytosis of LDL into peripheral cells.
  • Mnemonic: "Apo B100 makes you gain 100 pounds."

• Apo E, Apo C2, and Apo B48:

  • Previously discussed.
  • Functions and mnemonics detailed in earlier parts.

• Apo A1 and HDL Activation:

  • Nascent HDL is secreted first, needs activation.
  • Apo A1 activates lecithin-cholesterol acyltransferase (LCAT) to convert nascent HDL into mature HDL.
  • Mnemonic: "Apo A1 activates awesome fat."

HDL vs. LDL

• HDL (High-Density Lipoprotein):

  • Known as "good cholesterol."
  • Transports cholesterol from peripheral cells to the liver.
  • Mnemonic: HDL is "Hepatic Delivery" (periphery to liver).

• LDL:

  • Transports cholesterol from the liver to peripheral cells.
  • Mnemonic contrast with HDL.

Summary

• Understand the pathways: VLDL to IDL to LDL.
• Focus on the roles of Apo proteins.
• Recognize the differentiating factors between HDL and LDL.
• Use mnemonics for memory aid on lipid transport pathways.

Conclusion

• Complex yet crucial pathways in biochemistry.
• Importance of understanding roles and conversions of lipoproteins in lipid transport.
• Mnemonics and summary aids for efficient learning and application in exams.