Triacylglycerol: Structure & Function Video

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  • 0:00 Energy Reserves and Function
  • 1:45 Structure
  • 3:05 Fat DIgestion
  • 3:40 Lesson Summary
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Lesson Transcript
Instructor: Catherine Paul

Catherine has taught high school science and has a master's degree in biology.

Find out why triacylglycerol, more commonly known as fat, is important for our health. Explore the structure of triacylglycerol and how its chemical properties provide us with the energy our bodies need.

Energy Reserves and Functions

Let's start with a riddle: Name one thing many of us have and want to lose? The answer: fat!

Fat commonly gets a bad rap when it comes to our health. But the truth is, our bodies are designed to have a fat reserve of around 21% for men and 26% for women. When our bodies undergo long periods of food shortages, the fats found in triacylglycerol, a combination of fatty acids and the chemical compound glycerol, serve as an energy resource. For example, your body has a day's worth if sugar reserves, but once is has used that up your body will turn to your adipose tissue, a connective tissue that sores fat, to survive.

But why do we need fat for energy? Why can't we just store sugar?

Fat is special in that it can produce six times the energy of the same amount of common sugar. When our body gets the signal that our blood sugar supply is low, fat is released into the bloodstream.

Fats are also very easy to store because they are non-polar and water insoluble, which means they cannot be dissolved in water. As a result, we don't need to combine our fats with water in order to store them. For example, a piece of butter dropped into a glass of water would remain intact, while a spoonful of sugar would dissolve in water. Animals have special cells called adipocytes, which both create fat and store it in fat globules within the cell.

Adipose tissue, found mostly just under our skin, functions not only as energy reserves, but also as thermal insulation, to keep our bodies warm in lower temperatures. Warm-blooded water animals, such as whales, seals and penguins, need a substantial fat layer to keep them warm in cold climates.


We get our dietary fat from plants, fish and animals, mostly in the form of triacylglycerols, or triglycerides, typically made by the pancreas. Let's break that big word down. We'll start with the prefix, 'tri', which refers to the three fatty acids. At the end of the word, we have glycerol, a sugar alcohol composed of one glycerol unit.

Triglyceride structure
Triglyceride Structure

You may have heard the terms 'saturated' and 'unsaturated' fat in reference to food sources. Triacylglycerols can vary in the length of their fatty acid chains and the saturation level of those chains. Saturation refers to the extent of the hydrogen (H) bonds: to say that a fat is 'saturated' means that it has all the hydrogen bonds possible.

Butter Contains Saturated Fat
Butter Contains Saturated Fat

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