What are Lipids and Fats? | Types, Definition, Structure, Function & Facts

What are Lipids?

Lipids are one of the four main groups of organic molecules; the other three are proteins, nucleic acids (DNA) and carbohydrates (sugars). Lipids are made up of the same elements as carbohydrates: carbon, hydrogen, and oxygen. However, lipids tend to contain more hydrogen atoms than oxygen atoms.

Lipids include fats, steroids, phospholipids, and waxes. One of the main characteristics of lipids is that they are insoluble in water.

What are they doing?

Lipids play an important role in living organisms. Some of their main functions include energy storage, hormones, and cell membranes.

Types of Lipids

Of these two main lipids, there are many specific lipids, important for life, including fatty acids, triglycerides, glycerophospholipids, sphingolipids, and steroids. They are generally classified into simple lipids and complex lipids.

Simple Lipids

Esters of fatty acids with different alcohols.
  • Fats: Esters of fatty acids with glycerol. Oil is fat in a liquid state
  • Waxes: Esters of fatty acids with higher molecular weight monofunctional alcohols.

Complex Lipids

Fatty acid esters contain groups in addition to alcohols and fatty acids.
Phospholipids: These are lipids that contain, in addition to fatty acids and alcohols, a phosphate group. They often have nitrogenous bases and other substituents, for example, in glycerophospholipids, alcohol is glycerol, and in sphingophospholipids, alcohol is sphingosine.Glycolipids (glycosphingolipids): Lipids containing fatty acids, sphingosine, and carbohydrates.

Other Complex Lipids: Lipids such as sulfolipids and aminolipids. Lipoproteins can also be classified in this category.

What is Fat?

Fats are made up of one glycerol molecule and three fatty acid molecules. This compound is called a triglyceride. Like all fats, fat molecules are made up of the elements carbon, hydrogen, and oxygen. Fat is used as stored energy in our body.

Are all fats bad? No, in fact, fat is necessary for our body to be healthy. We cannot live without some fat in our diet. Most people should get about 20-30% of their diet from fat. However, too much fat may not be good for you. This can lead to excess weight and clog your arteries.

Types of Fats

There are two main types of fat: Saturated fat and Unsaturated fat.

Saturated Fat – Saturated fat is a solid at room temperature. These fats tend to come from foods like red meat, cheese, and butter. Saturated fats are sometimes called “bad” fats because they are known to cause high cholesterol, clog arteries and even increase the risk of certain cancers.

Unsaturated Fats – Unsaturated fats are liquid at room temperature. These fats tend to come from foods like nuts, vegetables, and fish. Unsaturated fats are considered much better for you than saturated fats and are sometimes referred to as “good” fats.


Waxes are similar to fats in their chemical composition, but they only have a long chain of fatty acids. The wax is soft and pliable at room temperature. They are produced by animals and plants and are often used for protection. Plants use waxes to help prevent dehydration. Humans have earwax to help protect the eardrum.


Steroids are another major group of lipids. Steroids include cholesterol, chlorophyll, and hormones. Our bodies use cholesterol to make the hormones testosterone (male hormone) and estrogen (female hormone). Chlorophyll is used by plants to absorb light for photosynthesis.

Are steroids bad for you?

Not all steroids are bad. Our bodies need steroids like cholesterol and cortisol to survive, so some steroids are good for us. There are also many steroids that doctors use to help people who are sick. However, the steroid you hear about in sports, the anabolic steroid, can be very bad for you. They can cause all kinds of harm to your body, including stroke, kidney failure, blood clots, and liver damage.


Phospholipids are the fourth major group of lipids. They are very similar to fats in their chemical composition. Phospholipids are one of the major structural components of all cell membranes.

Interesting facts about Lipids

When a compound is insoluble in water, it is said to be “hydrophobic”.

Bees use wax to make their hive.

Waxes are used in all sorts of everyday applications, including chewing gum, varnishes, and candles.

Fats help us dissolve and store several important vitamins, including A, D, E, and K.

Cortisol is a steroid that our bodies use to regulate energy and fight disease.

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