Lipids are important for our body’s functions. They work together with proteins and carbohydrates in many ways. Let’s look at some key roles they play:

1. Energy Storage and Use:

   • Triglycerides are a type of lipid made of glycerol and three fatty acids. They are the main way our body stores energy, especially in fat tissue. When we need energy, triglycerides release about 9 calories per gram. This is more than carbohydrates, which give us 4 calories per gram.

2. Cell Membrane Structure:

   • Phospholipids are another kind of lipid. They create layers that form the walls of our cells. These layers help keep different parts of the cell separate. Because of their special design, phospholipids allow some things to pass through while keeping others out. This affects how cells communicate and respond to signals.

3. Sterols and Hormones:

   • Cholesterol is a type of sterol that is important for making hormones like testosterone and estrogen. It also helps keep cell membranes flexible. Surprisingly, more than 25% of the weight of our brain comes from cholesterol!

4. Lipid Signaling:

   • Fatty acids can act like signals in the body. For example, arachidonic acid is important for creating substances called eicosanoids, which help the body respond to inflammation.

All these roles show just how essential lipids are for our body's energy use, cell structure, and communication.