Learning unit 13 is talking about the fatty acids and lipids. Lipids are biomolecules which soluble in organic solvents. It contains hydrocarbon side chain, which serve as energy store. When it performs in the bilayer form, it is essential component of biological membranes. It also plays role as intra and intercellular signaling molecules. There are 2 types of lipid, which categorized based on polarity, non-polar lipid and polar lipid.
Lipids are grouped into fatty acids, triacylglycerols, glycerophospholipids, sphingolipids and steroids, eicosanoids and lipid soluble vitamins.
First and foremost, I learnt that there are 2 groups of fatty acids, which are saturated chains and unsaturated chains. Saturated chains of fatty acids pack tightly to form more rigid membranes, whereas unsaturated fatty acid chains bend and pack in less ordered way and with greater potential for motion. Saturated fatty acids are important to nutrition because of their ability to elevate blood lipid levels in humans. Saturated fatty acids are not essential because the body can synthesize these fatty acids. Hence, saturated fatty acid intake be kept low as excessive intake will elevate the blood lipid level. Unsaturated fatty acids are a component of the phospholipids in cell membranes and help maintain membrane fluidity.
Then, triacylglycerols (TAG) are triesters of glycerols. It acts as energy storage, which fat content of normal humans allows them to survive from starvation for 2 to 3 months. TAG also can be used for insulation and saponification to produce soap.
Glycerophospholipids are major lipid component of biological membranes. They are amphiphilic molecules with non-polar aliphatic tails and polar phosphoryl-X heads. Glycerophospholipid is to serve as a structural component of biological membranes. They function in signal induction and transport, and also provide the precursors for prostanglandins and other leukotrienes. They acts as transporters due to their roles as storage centers for secondary messengers in the membrane.
Sphingolipids are major membrane components and they are derivatives of C18 amino alcohol sphingosine. Common examples of sphingolipids are sphingomyelins, cerebrosides, and gangliosides. Sphingomyelines are major components of myelin, which surrounds and insulate nerve cells for normal impulse transmission. Gangliosides constitue 6% of brain lipids and act as receptors for pituitary glycoprotein hormones to regulate physiological functions.
Steroids are biomolecules with three 6-membered rings and one 5-membered ring that are all fused together. Cholesterols are the most common steroids in animals and provide precursors for all other steroids in animals. Steroids are important in salt balance, metabolic and sexual functions.
Eicosanoids are signaling molecules, which made by oxidation of C20 essential fatty acids. They are derived from omega-3 or omega-6. They play important role in inflammation or immunity, and act as messengers in central nervous system. At low concentration of eicosanoids, they regulate blood pressure and help in blood coagulation.
They are 4 classes in lipid soluble vitamins, which are vitamin A, vitamin D, vitamin E and vitamin K. Vitamin A are unsaturated organic compounds which includes retinol and helps in visual cycle of rod cells. Vitamin D regulate metabolism of calcium and phosphorus. Vitamin E acts as important antioxidant to trap radicals. Vitamin K ensure proper blood coagulation.
After learning this learning unit, I find out actually there are so many different classes of lipids and their different functions in daily life. For example, i never realized that our brain and nerves are mainly composed of and functioned normally by lipid such as sphingolipids. In conclusion, I had learnt so many knowledge about the types and functions of different types of lipids and fatty acids in this chapter and I am able to relate the knowledge that I learnt in my daily life.
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