Why lipids matter
Six of the jobs lipids do are the ones worth knowing.
1. As an energy source
Like carbohydrates and proteins, lipids are an energy source. But gram for gram, burning fat releases more energy.
2. Building structural components
Lipid is the main compound in all cell membranes, especially the plasma membrane. The important ones here are phospholipids and cholesterol.
3. Conserving water
Plant surfaces carry a waxy layer called cutin, which stops water escaping. Many animals have wax in their body covering too, which prevents dehydration. Lipids are impermeable to water.
4. Maintaining body temperature
In warm-blooded animals such as birds and mammals, the subcutaneous fat layer under the skin acts as a heat insulator. It is thicker in animals living in cold environments.
5. Protecting internal organs
The fat layers around internal organs absorb shocks from outside. They act as a protective cushion.
6. Synthesising certain hormones
Lipids are needed to synthesise some vertebrate hormones. Examples: oestrogen, testosterone, cortisone.
Remember
Carbohydrates = immediate fuel. Lipids = long-term fuel and insulation. Proteins = machinery and building material.