Cholesterol

usually people when they start talking about cholesterol the first thing that comes to their mind is the bad part of the cholesterol, but let us talk about the good part of the cholesterol.

cholesterol is:

• contains 27 carbons
• is white substance 
• part of the biological membranes (very important constituent of our cells). 
• can be used by adrenal cortex or gonads to makes steroids hormones such as corticosteriods hormones.
• also can be used to make bile acids, Vitamin D (which is a fat-soluble vitamin)

cholesterol is also very important for the process of learning and memory. surely there are some areas of cholesterol metabolism and its function that make it bad substances. as we know cholesterol level rise in the blood some times and depending on the type of cholesterol may have dangerous consequences.

diet that contains cholesterol can be absorb through the intestinal of epithelium, of course cholesterol is not absorbed in the form of free cholesterol, its usually rather involved in metabolism of liporpoteins and the major one here is chylomicrone which is formed in the intestine.

chylomicrones are particles that contain largerly triacylglycerols plus phospholipids and some cholesterol, so cholesterol is not the only lipid that found there, but when TAGs are hydrolyzed by lipoprotein lipase which is found the capillaries, the remnant protein of chylomicrone is going to have high level of cholesterol

lipoprotein lipase is a very important enzyme and you have to remmber two thing about this enzyme:

• found in capillaries
• its activated only by insulin action

people usually eats lipids with carbohydrates, this will increase insulin secrtion and lipoprotein lipase is activated and the chylomicrone is hydrolyzed leaving chylomicrone remnant which is utilized by many tissues, in a major way by receptors that expressed very well on the membrane of hepatocytes.

the exogenous cholesterol that was found in the diet, will be apart of the hepatic pool of cholesterol these particles of  cholesterol will inhibit the cholesterol biosynthesis in the liver.

this pathway cholesterol biosynthesis account for 60% of all cholesterol in the body.

so the majority of the cholesterol thats found in the body belongs to the endogenous cholesterol rather than exogenous one.