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. Living organisms have a number of carbon compounds in which heterocyclic rings can be found. Some of these are nitrogen bases – adenine, guanine, cytosine, uracil, and thymine. When found attached to a sugar, they are called nucleosides.
If a phosphate group is also found esterified to the sugar they are called nucleotides. Adenosine, guanosine, thymidine, uridine and cytidine are nucleosides. Adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid are nucleotides. Nucleic acids like DNA and RNA consist of nucleotides only.
DNA and RNA function as genetic material. Cholesterol Phospholipid (Lecithin) Fats and oils (lipids) (CH ) CH COOH Fatty acid (Palmitic acid) Glycerol Triglyceride (R , R and R are fatty acids) Nitrogen bases Adenine OCH P HO Adenylic acid Nucleotide HOCH Adenine HOCH Uracil Adenosine Uridine Nucleosides HOCH HO CH OH C H O (Glucose) C H O (Ribose) Sugars (Carbohydrates) Serine Glycine Amino acids Alanine Figure . Diagrammatic representation of small molecular weight organic compounds in living tissues HN N H Adenine (Purine) Uracil (Pyrimidine)