By Fats and oils belong to this group. Lipids which are solid at room temperature are called fats and liquids are called oils. Similar to carbohydrates, fats also contain Carbon, Hydrogen and Oxygen as constituent elements. But a lipid contains much less oxygen than a carbohydrate. Lipids are insoluble in polar solvents including water. They are soluble in organic solvents.
Ground nut, coconut, gingelly, butter and margarine are examples for foods which contain lipids.
Fatty acids and glycerol react to form Lipids.
Significance of Lipids
- As an energy source
- Lipids act as an energy source as carbohydrates and proteins. More energy is produced during burning of lipids.
- To form different structural components
- Lipid is one of the most important compounds in cell membrane. (Specially phospho lipids and cholesterol)
- For conservation of water
- The wax known as cutin present on the surface of the plant body conserve water. Most animals’ body covering also contains wax which helps to avoid desiccation as it is impermeable to water.
- To maintain the body temperature
- arm blooded animals such as birds and mammals possess a hypodermal fat layer which acts as a thermal insulator. It helps to maintain their body temperature.
- To protect internal body organs
- The fat layer surrounds the organs and structures in the body and absorbs external shocks. Thereby provides protection.
- To synthesize some hormones
- Some Hormones of vertebrates (Oestrogen, Testosterone, Cortisone) are lipid compounds.
Test to identify lipids
Sudan III test
- Some amount of gingelly oil or coconut oil is added into a test tube.
- Sudan III reagent is added into it.
- Appearance of red fat globules
Fatty acids can be divided into two groups as follows.
Saturated fatty acids
fatty acids which contain only single bonds within Carbon atoms are called saturated fatty acids. Saturated fatty acids exist in room temperature as solids or semi-solids.
Unsaturated fatty acids
fatty acids which contain one or several double bonds within Carbon atoms are called unsaturated fatty acids. Unsaturated fatty acids exist in room temperature as liquid
