Lipids are fats and oils. Chemically speaking, fats and oils are the same type of compound, which is why we use the word 'lipid' to refer to them collectively.

The only difference between fats and oils is what state of matter they are at room temperature. Lipids that are solid at room temperature are called fats, and lipids that are liquid at room temperature are called oils.

Photograph of a small glass vial filled about three quarters of the way up with orangey-yellow liquid.

Sample of oil extracted from wheat seeds. This oil is a mixture of lipids.

Functions of lipids

Lipids have many important functions in living organisms, including the following:

  • They are a component of membranes
  • They are used to store energy
  • They are used for thermal insulation
  • They are used for electrical insulation
Photograph of a polar bear walking over snow-covered ground. The are some leafless shrubs sticking out of the snow.

Polar bears have a thick layer of fat under their skin which provides them with thermal insulation. This is necessary as they usually live in very cold environments.


Triglycerides are a common group of lipids.

A triglyceride is made of four molecules bonded together. One of these is a molecule called glycerol. The other three are molecules called fatty acids. The three fatty acids are all bonded onto the glycerol.

Diagram of the structure of a triglyceride. The diagram consists of four rectangles with words in them. There is a vertical rectangle on the left with the word 'Glycerol' in it. On its right, three horizontal rectangles are attached to it, one on top of the other. They each have the words 'Fatty Acid' written in them. Each fatty acid rectangle is joined to the glycerol rectangle by a horizontal line.

The structure of a triglyceride.


Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.


What are lipids?


What is the difference between a fat and an oil?


What are triglycerides? What is their structure?


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