Test for the presence of lipids (LC 2026) (Leaving Cert Biology): Revision Notes

Test for the presence of lipids

Background:

Lipids are biomolecules with triglycerides as their subunits, composed of glycerol and three fatty acids.

• In living organisms, lipids provide protection, insulation, and energy.
• In cells, lipids are found in the cell membrane as phospholipids. A phospholipid has glycerol, two fatty acids, and phosphorus. There are two types of lipids: fats and oils. Oils are liquid at room temperature, while fats are solid.

Materials needed:

• Food sample
• Distilled water (control)
• Brown paper
• Direct light source

Method:

1. Rub food sample on brown paper.
2. Hold paper up to direct light.
3. Record result.
4. Repeat for control sample using distilled water. Wait for a period of time after adding water before checking for the presence of a translucent spot to allow water to dry/evaporate.

Result:

A positive result for the presence of a lipid is that the brown paper will form a permanent translucent spot where the lipid has been placed on the brown paper.

With the control, the translucent stain disappears.