Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 8 : Lipids- Introduction, Classification and Functions

Functions

1. Structural component of cell membrane and maintains its fluidity.
2. Energy storage: Triacylglycerols, stored in adipose tissue, are a major form of energy storage in animals
3. Signaling: In recent years evidence has emerged showing that that lipid signaling is a vital part of the cell signaling.
4. Other Functions involve: The "fat-soluble" vitamins (A, D, E and K) – which are isoprene-based lipids – are essential nutrients stored in the liver and fatty tissues, with a diverse range of functions. Acyl-carnitine are involved in the transport and metabolism of fatty acids in and out of mitochondria, where they undergo beta oxidation.

Most of the lipid found in food is in the form of triacylglycerols, cholesterol and phospholipids. A minimum amount of dietary fat is necessary to facilitate absorption of fat-soluble vitamins (A, D, E and K) and carotenoids Humans and other mammals have a dietary requirement for certain essential fatty acids, such as linoleic acid(an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid) because they cannot be synthesized from simple precursors in the diet. Both of these fatty acids are 18-carbon polyunsaturated fatty acids differing in the number and position of the double bonds. Most vegetable oils are rich in linoleic acid (safflower, sunflower, and corn oils). Alpha-linolenic acid is found in the green leaves of plants, and in selected seeds, nuts and legumes (particularly flax, rapeseed, walnut and soy). Fish oils are particularly rich in the longer-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A large number of studies have shown positive health benefits associated with consumption of omega-3 fatty acids on infant development, cancer, cardiovascular diseases, and various mental illnesses, such as depression, attention-deficit hyperactivity disorder, and dementia. In contrast, it is now well-established that consumption of trans fats, such as those present in partially hydrogenated vegetable oils, are a risk factor for cardiovascular disease.