4.3.1: What is Cholesterol?

Casey Housman - ABS 8th

LDL Cholesterol

LDL Cholesterol: is considered the “bad” cholesterol because it contributes to plaque, a thick, hard deposit that can clog arteries and make them less flexible. This condition is known as atherosclerosis. If a clot forms and blocks a narrowed artery, heart attack or stroke can result

Structure: Approximately 50 percent of the weight of an LDL particle is cholesterol and only 25 percent is protein. Low-density lipoproteins contain proteins called B-100 proteins. The type of protein is significant because it determines the function of the lipoprotein particle.

Function: Low-density lipoproteins and high-density lipoproteins both transport cholesterol in the blood, but the main functional difference between the two is they deliver cholesterol to different parts of your body. Low-density lipoproteins -- the primary carriers of cholesterol -- bring cholesterol to cells throughout your body and can cause cholesterol to buildup within your arteries. This buildup can eventually lead to arterial blockage and an increased risk for heart disease and stroke.

HDL Cholesterol

•HDL Cholesterol: is the well-behaved "good cholesterol." This friendly scavenger cruises the bloodstream. As it does, it removes harmful bad cholesterol from where it doesn't belong. High HDL levels reduce the risk for heart disease -- but low levels increase the risk.

•Structure: High-density lipoprotein particles consist of 20 percent cholesterol by weight and 50 percent protein. HDL particles contain mostly A-I and A-II proteins. Since protein is more dense than fat, HDL particles are more dense than LDL particles, hence the names "high-density" and "low-density" lipoproteins. The type of protein is significant because it determines the function of the lipoprotein particle.

•Function: High-density lipoproteins can benefit your health because these particles carry cholesterol away from your heart and other organs and deliver it back to your liver, where it is passed from your body.

Questions about HDL and LDL Cholesterol

Why do doctors monitor the concentrations of LDL and HDL in patient's blood? During a blood test, LDL and HDL are both monitored along with other things because they are used to help evaluate the patient's risk of heart disease. Whether more cholesterol is being taken to or from cells can be determined during a blood test. HDL levels should be at least 40mg/dL or closer to 60mg/dL. LDL should be lower than 129mg/dL or even lower for people that are at higher risks for heart disease.

How are concentrations of LDL and HDL associated with the risk for heart disease? An excess of LDL can result in plaque buildup on arterial walls which can ultimately result in atherosclerosis. That is the hardening of the arteries and can lead to heart diseases like a heart attack or stroke. Unlike LDL, higher HDL levels can actually lower the risk of heart disease.

What other molecules in a patient’s blood are monitored along with LDL and HDL? - triglycerides
- blood sugar level
- total cholesterol

What do the results of a cholesterol test mean? How do patients interpret each value? It gives information about total cholesterol, LDL (bad) cholesterol, HDL (good) cholesterol and triglycerides. Your test report will show your cholesterol levels in milligrams per deciliter of blood (mg/dL). To determine how your cholesterol levels affect your risk of heart disease, your doctor will also take into account other risk factors such as age, family history, smoking and high blood pressure.

What can patients do to change the levels of LDL and HDL in their blood?

Patients can primarily change their diet in order to change the LDL and HDL levels in their blood. The end goal should be to lower your LDL while increasing the HDL. Different foods can have an effect on each component of cholesterol. Losing weight is another way to change cholesterol levels.
How does intake of unsaturated, saturated, and trans fats affect cholesterol levels and overall health?

Unsaturated- Can improve cholesterol levels, decreasing your risk for cardiovascular disease. Polyunsaturated fats include omega-3 and omega-6 fatty acids, which are essential fats your body needs. Eating a diet that includes good sources of polyunsaturated fat can lower your blood pressure, protect against irregular heartbeats and lower your risk for Type 2 diabetes, Your body relies on omega-3 and omega-6 fatty acids for proper brain development and function.

Saturated - Unhealthy for your body and may increase your risk of Type 2 diabetes. It may also increase your risk of heart disease by increasing your LDL, or "bad," cholesterol. saturated fat is the main dietary cause of high LDL cholesterol.

Trans Fat- Most unhealthful type of fat. Trans fat can both increase your LDL cholesterol and decrease your HDL, or "good," cholesterol, thus increasing your risk of heart disease. Additionally, consuming trans fat can increase the inflammation in your body, which may increase your risk of cardiovascular disease and Type 2 diabetes, and it can lead to insulin resistance. For every 2-percent increase in daily calories from trans fat, risk of coronary heart disease increases by 23 percent.


•Cholesterol a compound of the sterol type found in most body tissues, including the blood and the nerves. Cholesterol and its derivatives are important constituents of cell membranes and precursors of other steroid compounds, but high concentrations in the blood (mainly derived from animal fats in the diet) are thought to promote atherosclerosis.

•Structure four linked hydrocarbon rings forming the bulky steroid structure. There is a hydrocarbon tail linked to one end of the steroid and a hydroxyl group linked to the other end. The hydroxyl group is able to form hydrogen bonds with nearby carbonyl oxygen of phospholipid and sphingolipid head groups. Cholesterol is known as a "sterol" because it is made out of a alcohol and steroid. Cholesterol is present in most animal membranes with varying amounts but is absent in prokaryotes and intracellular membranes.