Lipids Structure and Classification — NEET Biology
✅ Asked in NEET 2024Lipids are generally water insoluble. They could be simple fatty acids. A fatty acid has a carboxyl group attached to an R group. The R group could be a methyl (–CH₃), or ethyl (–C₂H₅) or higher number of –CH₂ groups (1 carbon to 19 carbons). For example, palmitic acid has 16 carbons including carboxyl carbon. Arachidonic acid has 20 carbon atoms including the carboxyl carbon. Fatty acids could be saturated (without double bond) or unsaturated (with one or more C=C double bonds). Another simple lipid is glycerol which is trihydroxy propane. Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They can be then monoglycerides, diglycerides and triglycerides. These are also called fats and oils based on melting point. Oils have lower melting point (e.g., gingelly oil) and hence remain as oil in winters. Can you identify a fat from the market? Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found in cell membrane. Lecithin is one example. Some tissues especially the neural tissues have lipids with more complex structures.
NTA tests lipid classification based on structure, especially the distinction between simple lipids (fatty acids, glycerol, triglycerides) and complex lipids (phospholipids). Students often confuse saturated vs unsaturated fatty acids or fail to identify which lipids contain phosphorus. The key trap is assuming all lipids have glycerol—phospholipids do, but some complex neural lipids have different structures. To score: remember that triglycerides = 3 fatty acids + 1 glycerol, phospholipids = glycerol + fatty acids + phosphate group + organic compound, and that melting point differences (oils vs fats) depend on saturation levels. Focus on structural composition rather than just definitions.
This paragraph was tested 4 times in NEET.
Lecithin, a small molecular weight organic compound found in living tissues, is an example of:
Following are the statements with reference to 'lipids': (NEET 2021) a) Lipids having only single bonds are called unsaturated fatty acids. b) Lecithin is a phospholipid. c) Trihydroxy propane is glycerol. d) Palmitic acid has 20 carbon atoms including carboxyl carbon. e) Arachidonic acid has 16 carbon atoms. Choose the correct answer:
A typical fat molecule is made up of (NEET 2016 Phase 1)
Which of the following are not fatty acids? A. Glutamic acid B. Arachidonic acid C. Palmitic acid D. Lecithin E. Aspartic acid Choose the correct answer from the options given below:
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