Cholesterol is synthesized in the liver, the body needs a small amount to help perform certain task's and build certain structures, it is an important constituent of the plasma membrane of cells.
High density lipoprotein or HDL is called good cholesterol because it contains more protein than lipids. HDL binds fats in the bloodstream and transports them to the liver where they are eliminated from the body. An increased percentage of serum HDL is associated with a decreased risk of cardiovascular disease.
Low density lipoprotein or LDL is called bad cholesterol because it has a higher percentage of lipids than protein. LDL is transported to all body cells. An increased amount of serum LDL is associated with an increased risk of cardiovascular disease.
Bad cholesterol, also known as LDL (low density lipoprotein), can build up in the arteries over time and cause many serious health issues. This build up is called plague and leads to atherosclerosis. So for this reason, it is considered "bad" cholesterol.
Good cholesterol, also known as HDL (high density lipoprotein), helps protect the body against heart attacks. Experts believe that HDL actually helps the body to rid itself of LDL and even slows plaque from building up in the arteries. For these reasons it is considered "good" cholesterol because it helps the body.
Cholesterol is a fatty substance present in all animal tissues. It belongs to a class of chemicals which are a type of lipid. In humans cholesterol makes up an important part of membrane of each cell in the body. Cholesterol is also essential in making of bile acid produced by the liver, and in making of certain hormones.
In addition, the liver uses cholesterol to make bile acids, which aid digestion. The body also uses cholesterol in the production of certain hormones. Hormones are chemical substances that influence many body activities.
Cholesterol is carried in the bloodstream in large molecules called lipoproteins. There are two such types of lipoproteins called low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Accordingly, the cholesterol in blood can be identifies a either LDL-cholesterol or HDL-cholesterol. High level of LDL-cholesterol is primarily responsible for forming deposits of cholesterol in arteries, that is a major cause of heart attacks. For this reason LDL-cholesterol is labeled by some as bad cholesterol. In contrast, HDL cholesterol is called good cholesterol.