What Have You Learnt
1. Lipids are a heterogeneous group of compounds, including fats, oils,steroids, waxes, and related compounds and can be divided in two major classes as nonsaponifiable and saponifiable lipids.
2. Saturated fatty acids do not have any double bonds. Animal fats are a source of saturated fatty acids. Unsaturated fatty acids can have one or more double bonds along its hydrocarbon chain. Plants are the source of unsaturated fatty acids.
3. Fatty acid that cannot be synthesized by the body is an essential fatty acid. Linoleic and linolenic are the two essential fatty acids (both are unsaturated). Nonessential fatty acids can be made by the human body and so do not need to be obtained from diet alone.
4. Animal fats (lard) contain a high amount of saturated triglycerides while plant oils (vegetable oil) contain a high amount of unsaturated triglycerides. While neither is healthy when consumed in excess, vegetable oils are far healthier than lard.
5. Phospholipids are amphipathic lipids seen as a bilayer and form the structure in biologic membranes.
6. Cholesterol is a sterol and an important component of cell membranes. It is also the basis for the synthesis of other steroids, including the sex hormones estradiol and testosterone, as well as other steroids such as cortisone and vitamin D.
7. Cholesterol is insoluble in the blood, so when it is released into the blood stream it forms complexes with lipoproteins. Cholesterol can bind to two types of lipoprotein, called high-density lipoprotein (HDL) and low-density lipoprotein (LDL).
8. High levels of blood cholesterol are associated with plaque formation in the arteries, which can lead to heart disease and stroke.
9. The major lipids in the diet are triacylglycerols and, to a lesser extent, phospholipids. These are hydrophobic molecules and must be hydrolyzed and emulsified to very small droplets (micelles) before they can be absorbed.
10. The fat-soluble vitamins – A, D, E, and K – and a variety of other lipids (including cholesterol) are absorbed dissolved in the lipid micelles.
11. Bile salts, formed in the liver and secreted in the bile, enable emulsification of the products of lipid digestion into micelles and liposomes together with phospholipids and cholesterol from the bile. Because the micelles are soluble, they allow the products of digestion absorbed at the intestinal region.
12. Low density lipoprotein (LDL), high density lipoprotein (HDL), very low density lipoprotein (VLDL), and intermediate density lipoprotein (IDL) are the types of lipoprotein.
13. Ketogenesis occurs when there is a high rate of fatty acid oxidation in the liver. Acetoacetate, ß-hydroxybutyrate and acetone are the products of fatty acid oxidation.
14. Atherosclerosis is linked to high levels of cholesterol in the blood, and particularly to high levels of LDL-bound cholesterol; there is a negative correlation between HDL levels and arterial disease. LDL-cholesterol is called as bad cholesterol and HDL-cholesterol is called as good cholesterol
Terminal Questions
1. Classify lipids with suitable examples.
2. What are essential and nonessential fatty acids.
3. Write short on importance of cholesterol.
4. Write short note on digestion and absorption of lipids.
Answers To Intext Questions
I. 1. (b) 2. (c) 3. (a) 4. (a) 5. (a)
II. 1. Nonpolar lipids
2. Unsaturated
3. Micelles
4. Proteins
5. Glycerol and free fatty acid
III. 11. (c) 12. (e) 13. (d) 14. (a) 15. (b)
