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⚗️biological chemistry ii review

Intermediate-density lipoproteins (IDL)

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Intermediate-density lipoproteins (IDL) are a type of lipoprotein that are formed during the metabolism of very-low-density lipoproteins (VLDL) in the bloodstream. They play a key role in the transport of cholesterol and triglycerides within the body, bridging the gap between VLDL and low-density lipoproteins (LDL) in terms of density and composition.

5 Must Know Facts For Your Next Test

  1. IDL are formed when VLDL particles lose triglycerides through the action of lipoprotein lipase, resulting in a higher density particle rich in cholesterol.
  2. IDL particles have a density range between 0.95 and 1.006 g/mL, which makes them less dense than LDL but denser than VLDL.
  3. The metabolism of IDL involves their further conversion to LDL or their uptake by the liver, which helps regulate lipid levels in the bloodstream.
  4. Elevated levels of IDL in the blood can be indicative of metabolic disorders or dyslipidemia, which are risk factors for cardiovascular diseases.
  5. IDL particles carry apolipoproteins such as apoE and apoB-100, which play crucial roles in their metabolism and interaction with liver receptors.

Review Questions

  • How do intermediate-density lipoproteins (IDL) contribute to the overall metabolism of lipoproteins in the body?
    • Intermediate-density lipoproteins (IDL) serve as a transitional form in the metabolism of lipoproteins. They are created from very-low-density lipoproteins (VLDL) after triglycerides are removed, making them richer in cholesterol. This process not only helps transport cholesterol through the bloodstream but also allows for further conversion into low-density lipoproteins (LDL), which can influence cholesterol levels and overall lipid health.
  • Discuss the role of IDL in relation to cardiovascular health and how their levels can impact disease risk.
    • IDL levels can significantly affect cardiovascular health due to their role in lipid transport and metabolism. Elevated IDL levels can indicate an imbalance in lipid profiles, which is associated with an increased risk of atherosclerosis and other cardiovascular diseases. Monitoring IDL, along with other lipoprotein types like LDL and HDL, provides insight into an individual's risk for heart disease and helps guide potential interventions.
  • Evaluate the significance of apolipoproteins present in intermediate-density lipoproteins (IDL) and their impact on lipid metabolism.
    • The apolipoproteins associated with intermediate-density lipoproteins (IDL), such as apoE and apoB-100, are critical for lipid metabolism. These proteins facilitate the binding of IDL to hepatic receptors, influencing their uptake by the liver or further transformation into LDL. Understanding these interactions helps clarify how alterations in IDL composition can affect overall lipid homeostasis and inform strategies for managing dyslipidemia.