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Phospholipids have a hydrophobic, “water hating,” hydrocarbon tails and hydrophilic, "water loving" phosphate groups on the end, so they are soluble in both water and oil.
Our cell membranes are made mostly of phospholipids arranged in a double layer with the tails from both layers facing inward and the heads facing outward, called the lipid bilayer.
These lipids are esters of alcohol, insoluble in water and difficult to hydrolyze, or break down.
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Cholesterol is a type of steroid, with a central core consisting of four fused rings, a characteristic shared by all steroids. Our bodies make about 2g of cholesterol per day, about 85% of blood cholesterol, while only about 15% comes from dietary sources.
Wax forms protective and waterproof layers on some plants, bacteria, animal fur and integuments of insects.
- animated tutorial and quiz from WH Freeman.
- animated tutorial from John Kyrk.
Cholesterol is precursor to sex hormones, such as testosterone and progesterone, and Vitamin D. Our cell membranes contain a lot of cholesterol which helps to keep the membrane flexible and fluid even when our cells are exposed to cooler temperatures.
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