Question

Discuss the different lipid fractions that may occur in the vascular system in animals? [6]

Answer 1

The lipid fractions that occurs in the vascular system in animals are:

1. Cholesterol
2. Triglycerides
3. High density lipoprotein

Cholesterol: It is an unsaturated alcohol. It is a fundamental element of all cell membrane. It is a precursor of various steroidal hormones and bile acids.

Triglycerides: These are the fatty acids of esters and represent the main lipid component of dietry fats and fat deposits of animals.

Cholesterol and triglycerides are non polar lipid substance that are insoluble in water. They are transported across the membrane with the help of lipoprotein. Increase or decrease level of cholesterol and triglycerides usually occurs because of abnormality in synthesis, transport and degradation of their lipoprotein particles.

lipoprotein: These are the small particles in blood which contains cholesterol, phospholipid, triglycerides and proteins. Lipoproteins are classified into five categories on the basis of their density:

• Very low density lipoprotein (VLDL): it contains high concentration of triglycerides and moderate concentration of cholesterol and phospholipid.
• Intermediate density lipoprotein(IDL): formed by the removal of large portion of triglycerides from VLDL by lipoprotein lipase. Concentration of cholesterol and phospholipid increases because of removal of triglycerides.
• Low density lipoprotein (LDL): formed from IDL by complete removal of triglycerides. The lipoprotein contains only cholesterol and triglycerides.
• High density lipoprotein (HDL): contains high concentration of protein and low concentration of phospholipids. All the lipoproteins are synthesized in liver and HDL in intestine also. The function of HDL is reverse transport of cholesterol from different tissues into the liver. And here it is eventually removed.
• Chylomicrons: fatty substance covered with protein coat.

Hyperlipoproteinemia is the lipid disturbance of major relevance of clinically because of its association with increase risk of atherosclerotic cardiovascular disease. Increase plasma concentrations of cholesterol and LDL have greater risk of coronary artery disease.