What is Cholesterol?

Ricci Abines & Malyka Janjua

What are LDL and HDL?

LDL (low density lipoprotein) and HDL (high density lipoprotein) are both types of lipoproteins. LDL is said to be the "bad" cholesterol. This is because it can help clog arteries and decrease their level of flexibility which can cause heart attacks. HDL is considered to be the "good" cholesterol because it removes the LDL cholesterol from arteries and delivers it to the liver.

the structures and functions of LDL and Hdl

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HDL particles are more dense than LDL particles because HDL consists of 50% protein and 20% cholesterol while LDL consists of 25% protein and 50% cholesterol.

LDL and HDL also contain different types of protein which significantly determines the function of the lipoprotein:

  • LDL contain B-100 proteins
  • HDL contain mostley A-I and A-II proteins

— Both LDL and HDL transport cholesterol, but they deliver cholesterol to different parts of the body:

  • LDL brings cholesterol throughout the body (but can cause buildup in the arteries, which can lead to arterial blockage and a higher risk of heart disease)
  • HDL brings cholesterol away from your heart and back to your liver (benefits your health)

Why do doctors monitor the levels of LDL and HDL in patients' blood?

Doctors monitor the levels of LDL and HDL in patients' blood because the levels help to see if the patient is at risk for cardiovascular disease or to see their blood's health status. Both LDL and HDL are monitored to see if cholesterol is being carried to and from the body cells and liver in the right amount.

LDL, HDL, heart disease, and related disorders

  • excessive levels can lead to atherosclerosis (arteries are clogged by plaque, making them less flexible) and heart attack and stroke may result
  • the atherosclerosis can lead to peripheral artery disease (arteries supplying blood to the legs are narrowed by plaque)


  • healthy levels reduces the risk of heart disease because it carries cholesterol away from the heart
  • low levels can increase the risk of heart disease
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What other molecules in a patients' blood are monitored along with LDL and HDL?

Another molecule in a patient's' blood that is monitored along with LDL and HDL is a triglyceride molecule. Triglycerides are a type of fat that it used to give energy to muscles and store energy. Doctors check for a high triglyceride count along with a high LDL count because it can increase your chances of having a heart disease.

Results and interpretation of the cholesterol test

A cholesterol test measures your cholesterol levels and looks at different types of fat in the blood. It gives you your total cholesterol, LDL, HDL, and triglycerides. You are recommended to keep track of your results each time you take the test.

the total blood cholesterol level:

  1. the desirable level ≤ 200 mg/dL
  2. high risk of heart disease ≥ 240 mg/dL

a standard cholesterol test measures three types of fats:

  • LDL
  1. those with levels ≤ 189 mg/dL should try lowering their LDL by 30-50%
  2. high risk of heart disease ≥ 190 mg/dL
  • HDL
  1. the desirable level > 60 mg/dL
  2. high risk of heart disease < 40 mg/dL
  • triglycerides
  1. normal level < 150 mg/dL
  2. high risk of heart disease = 200+ mg/dL

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

To change the levels of LDL and HDL in their blood patients can try to keep a healthy diet and do aerobic exercises regularly. This will help a patient lose weight and keep their LDL and HDL levels at the best level. HDl is supposed to be at about 60 mg per dL and LDL should be at under 100 mg per dL.

the relationship between unsaturated, saturated, and trans fats and cholesterol levels and overall health

Your diet ultimately affects your blood cholesterol levels, this includes unsaturated, saturated, and trans fats.

Saturated fats:

  • found in red meat and dairy
  • raises total cholesterol and LDL levels
  • reduce intake if you benefit from lowering your cholesterol

Trans fats:

  • should be eliminated completely
  • raises LDL and lowers HDL
  • increases risk of heart disease and stroke and type 2 diabetes

Unsaturated Fats:

  • improves your blood cholesterol
  • stabilize heart rhythms
  • may benefit insulin and blood sugar levels


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American Heart Association. (2015, January 12). Good vs. Bad Cholesterol. Retrieved March 13, 2016, from http://www.heart.org/HEARTORG/Conditions/Cholesterol/AboutCholesterol/Good-vs-Bad-Cholesterol_UCM_305561_Article.jsp#.VuHIruIrLIU

Kamps, A. (n.d.). How Do LDL and HDL Differ Structurally and Functionally? Retrieved March 13, 2016, from http://healthyeating.sfgate.com/ldl-hdl-differ-structurally-functionally-2003.html

World Heart Federation. (2016). Cholesterol. Retrieved March 13, 2016, from http://www.world-heart-federation.org/cardiovascular-health/cardiovascular-disease-risk-factors/cholesterol/

Hendrickson, K. (2015, April 23). Why Do Doctors Monitor the Concentration of LDL & HDL? Retrieved March 13, 2016, from http://www.livestrong.com/article/144497-why-do-doctors-monitor-the-concentration-of-ldl-hdl/

WebMD, LLC. (n.d.). Cholesterol and Triglycerides Blood Test Types. Retrieved March 13, 2016, from http://www.webmd.com/cholesterol-management/cholesterol-and-triglycerides-tests

Mayo Clinic Staff. (2016, February 02). Nutrition and healthy eating. Retrieved March 13, 2016, from http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fat/art-20045550