"The body absorbs lipids mostly within the small intestine. The gallbladder secrets a chemical called bile to aid in the breakdown of this fat. From there the fat is broken down farther by the enzymes the pancreas makes. The mixture of "fatty acids, partially digested triglycerides and bile form micelles" (Grosvenor & Smolin, 2006, p.128) this stimulates the absorption process. After the absorption the triglycerides are reassembled and the majority of the bile is returned to the liver ready to repeat the process."
Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Lipoproteins can be classified as High-density lipoproteins (HDL's) and Low-density lipoproteins (LDL's). LDL's are associated with artery and heart disease and are often referred to as "bad cholesterol". What determines the classification into these categories?
IT is density. However, the classifications are important, because the majority of the HDL is returned to the liver, and the LDL is not.
See Blood Transport in this article
http://en.wikipedia.org/wiki/Cholesterol
the health
1) type of fatty acid.
2) ratio of lipid:protein
3) amount of TG and cholesterol.
The classification of lipoproteins into high-density lipoproteins (HDLs) and low-density lipoproteins (LDLs) is determined by their composition and function in the body. Here's an explanation of how this classification occurs:
1. Lipoprotein Structure: Lipoproteins are spherical structures consisting of a core of cholesterol and triglycerides (fatty acids and glycerol) surrounded by a shell of phospholipids, proteins, and cholesterol. The composition and density of these lipoproteins differ, which leads to their classification.
2. Density: The density of lipoproteins is determined by the amount of protein in the structure relative to the amount of lipids. HDLs have a higher protein content and are therefore more dense, while LDLs have a higher lipid content and are less dense.
3. Lipoprotein Lipase (LPL) Activity: The activity of the enzyme lipoprotein lipase plays a crucial role in the metabolism of lipoproteins. LPL is located on the walls of blood vessels and breaks down triglycerides into free fatty acids and glycerol for uptake into cells. HDLs primarily acquire triglycerides from other lipoproteins through LPL activity, while LDLs primarily deliver triglycerides to tissues.
4. Reverse Cholesterol Transport: HDLs have an additional crucial function in what is called reverse cholesterol transport. HDLs remove excess cholesterol from peripheral tissues, like arterial walls, and transport it back to the liver for excretion, hence their "good cholesterol" classification.
5. Atherogenic Potential: LDLs, due to their higher lipid content, are more prone to oxidation and can accumulate in arterial walls, forming plaques. This process contributes to the development of atherosclerosis and increases the risk of heart disease, which leads to their "bad cholesterol" classification.
To summarize, the classification of lipoproteins into HDLs and LDLs is determined by their density, composition, functions, and their contributions to cholesterol metabolism and cardiovascular health. Understanding this classification is important in evaluating an individual's lipid profile and assessing their risk for heart disease.