Cholesterol and Lipoproteins Functions

Cholesterol and Lipids

• Cholesterol helps the body produce vitamin D and hormones, including estrogen, testosterone, and cortisol.
• It also helps build cells of the nervous system.
• Triglycerides are produced by the liver and intestines and are stored in fat cells, released into the bloodstream when the body needs energy.

Types of Lipoproteins and Functions

• High-density lipoprotein (HDL) is the "good" cholesterol, carrying cholesterol back to the liver to be flushed out of the body.
• High levels of HDL reduce the risk of cardiovascular disease.
• Low-density lipoprotein (LDL) is the "bad" cholesterol, increasing the risk of coronary artery disease, heart attacks, and stroke.
• LDL carries cholesterol that accumulates as plaque inside blood vessels, leading to atherosclerosis.
• Very low-density lipoproteins (VLDL) are also bad cholesterol, carrying triglycerides and cholesterol to tissues.
• Intermediate-density lipoproteins (IDL) are produced when VLDLs give up their fatty acids, then either removed by the liver or converted into LDL.
• Chylomicrons are large particles that transport triglycerides.
• Apolipoprotein A (Apo(a)) is a type of LDL that makes particles stickier, increasing the risk of cardiovascular problems.

Derived Lipids

• Derived lipids are obtained through the hydrolysis of group 1 and 2 lipids, possessing characteristics of lipids.
• Examples include vitamin A, fatty acids, and steroids.

Functions of Lipids

• Lipids serve as a storage form of energy.
• They help in the absorption of fat-soluble vitamins.
• Lipids are a structural component of cell membranes.
• They act as thermal insulators, protecting internal organs.
• Lipids also act as electric insulators in neurons.

Essential Fatty Acids (EFAs)

• EFAs are required for membrane structure and function.
• They are necessary for the transport of cholesterol.
• EFAs are involved in the formation of lipoproteins.
• They prevent fatty liver disease.
• EFAs are also needed for the synthesis of eicosanoids.

Rancidity

• Rancidity is the deterioration of fats and oils, resulting in an unpleasant taste.
• Fats containing unsaturated fatty acids are more susceptible to rancidity.
• Rancidity occurs when fats and oils are exposed to air, moisture, light, and bacteria.
• Hydrolytic rancidity occurs due to partial hydrolysis of triacylglycerols by bacterial enzymes.
• Oxidative rancidity is due to oxidation of unsaturated fatty acids.

Test for Purity of Fats and Oils

• Acid number is the number of milligrams of potassium hydroxide required to completely neutralize the free fatty acids present in 1 g of the oil or fat.
• Saponification number is the number of milligrams of potassium hydroxide required to hydrolyze one gram of fat or oil.
• Iodine number is the number of grams of iodine absorbed by 100 g of fat or oil, indicating the degree of unsaturation.
• Reichert-Meissl (RM) number is the number of ml of 0.1 N potassium hydroxide required to completely neutralize the soluble volatile fatty acids distilled from 5 g of fat.

Chemical Reactions of Fatty Acids

• Esterification: reacts fatty acids with alcohols to form esters and water.
• Fatty Acid Hydrolysis: reverses esterification, producing fatty acids from esters.
• Saponification: base-catalyzed hydrolysis of an ester, producing an alcohol and a soap.

Learn about the role of cholesterol in producing vitamin D and hormones, and the different types of lipoproteins and their functions in the body.