Lipid
Biochemistry · Cell Biology · Food Nutrition
Say it: LIP-id
A lipid is one of a varied group of biological molecules, including fats, oils, phospholipids, waxes and steroids, that do not dissolve in water.
Also: lipids
Definition
What is a lipid?
Lipids are a large and varied family of biological molecules grouped by a shared physical property rather than a shared structure. They are hydrophobic, meaning they do not mix with water, but they dissolve in nonpolar solvents such as ether or chloroform. This is because they are made mostly of carbon and hydrogen joined by nonpolar bonds. The main kinds students learn are fats and oils (triglycerides), phospholipids, steroids such as cholesterol, and waxes.
Lipids do several jobs. Triglycerides, built from glycerol and three fatty acids, store energy compactly and insulate the body. Phospholipids have a water-loving phosphate head and two water-avoiding fatty acid tails, so in water they line up into the double layer, or bilayer, that forms every cell membrane. Steroids serve as hormones, waxes waterproof leaves and feathers, and vitamins A, D, E and K are fat-soluble lipids that travel with dietary fat.
In medicine, the word turns up in the lipid panel, a routine blood test that measures cholesterol and triglycerides, which are carried through the blood in particles called lipoproteins.
Word parts
Where does the word “lipid” come from?
- lip-
- fatGreek lipos
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Terms that go with it
- Fatty acidA fatty acid is a long chain of carbon and hydrogen atoms with a carboxyl group at one end, and is the building block of fats, oils and phospholipids.
- CholesterolCholesterol is a waxy steroid lipid found in animal cell membranes and used to make steroid hormones, vitamin D and the bile salts that digest fat.
- Cell membraneThe cell membrane is the thin, flexible boundary of lipids and proteins that encloses every cell and controls what enters and leaves it.
- CarbohydrateA carbohydrate is a sugar or a chain of sugars, such as starch or cellulose, built from carbon, hydrogen and oxygen and used for energy and structure.
- MacronutrientA macronutrient is a nutrient needed in large amounts, namely carbohydrate, protein or fat, which together supply energy and the raw materials for growth.
- VitaminA vitamin is an organic compound that the body needs in small amounts for normal metabolism, growth and health, and must mostly obtain from food.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 3.3 Lipids
- LibreTexts Chemistry, Introduction to Organic and Biochemistry (Malik), 6.1 What are lipids?
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