WEBVTT

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Lipids are an essential part of life.

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They store energy in our bodies
and insulate us from the cold.

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Some lipids help in transmitting nerve impulses.

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Lipids are even found in the cell
membranes of all living things.

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Lipids are divided into three major classes:
triglycerides, phospholipids, and steroids.

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Triglycerides are what most people
think of when they hear the word lipid.

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A triglyceride molecule is made up of two parts:
a glycerol backbone and three fatty acids.

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Glycerol is a small molecule
with three hydroxyl groups.

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A fatty acid is made up of a long
hydrocarbon chain and a carboxyl group.

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When the three hydroxyl groups
react with the carboxyl groups,

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the fatty acids and the glycerol
come together to form a triglyceride.

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Triglycerides are commonly called fats.

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They are found in many foods, such
as butter, oil, nuts, and meats.

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The main function of triglycerides
in your body is energy storage.

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Triglycerides from food are stored in fat
cells until it is necessary for your body

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to break them down for energy.

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Phospholipids are complex molecules composed
of a phosphate head and two fatty acid tails.

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Phospholipids are essential to
living organisms because they

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are a major component in all cell membranes.

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They can also be found in foods such as
eggs, soy, milk, and some vegetable oils.

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Steroids make up a highly
diverse group of molecules.

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Though they may differ in structure, all
steroids are made up of four carbon rings.

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Three of the rings have six carbons,
while one ring has just five carbons.

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Steroids have many functions within the body.

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They form the foundation for many hormones,
such as testosterone, estrogen, and cortisol,

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as well as other compounds such
as cholesterol and vitamin D.

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