Chapter 15 - Lipids
15.1 - Lipids
- Lipids are not water-soluble biomolecules
- Lipid categories include waxes, glycerol triglycerides, glycerophospholipids, sphingolipids, and steroids.
15.2 - Fatty Acids
- Unbranched carboxylic acids are fatty acids that typically contain an equal quantity of carbon atoms (12 to 20).
- Saturated, monounsaturated, or polyunsaturated with two or double bonds may be fatty acids.
- Almost always the double connection is cis in unsaturated fatty acids.
15.3 - Waxes and Triacylglycerols
Wax is an ester of a fatty acid with a long chain of alcohol.
- Triacylglycerols are three long-chain fatty acid esters of glycerol.
Fats have higher melting points than most vegetable oils, which contain more saturated fatty acids.
15.4 - Chemical Properties of Triacylglycerols
- Triacylglycerol hydrogenation transforms double bonding into single bonding.
- Glycerol and fatty acids are produced when the ester bonds are hydrolyzed in triacylglycerols when strong acids are present.
- In saponification, glycerol and fatty acid salts are generated by triacylglycerol heated on a strong basis.
15.5 - Phospholipids
Glycerophospholipids are glycerol esters with two fatty acids and an amino alcohol phosphate.
Sphingomyelin forms an amide bond to fatty acid in amino alcohol sphingosine and a phosphodiester bonds to phosphate and amino alcohol.
15.6 - Steroids: Cholesterol, Bile Salts, and Steroid Hormones
- Steroids are lipids that contain the four-ring fused structure of the steroid nucleus.
- Cholesterol, bile salts, and steroid hormones are part of the steroids.
- Synthesized with cholesterol, bile salts mix and break them apart with water-insoluble fats during digestion.
- The triacylglycerides are transported from the intestines and liver, such as chylomicrons and LDL, to fat cells and muscles for storage and energy.
- HDL carries cholesterol from tissue to the liver for removal
- Steroid hormones are structurally closely associated with cholesterol and their synthesis depends upon cholesterol.
- For sexual properties and reproductive properties, sex hormones such as estrogens and testosterone are responsible.
- Adrenal corticosteroids, such as aldosterone and cortisone, regulate the cellular water balance and blood glucose.
15.7 - Cell Membranes
- The semi-permeable membrane which separates the cellular content from the external fluids is surrounded by all animal cells.
- The membrane consists of a lipid bilayer with two rows of phospholipids.
- The lipid bilayer contains proteins and cholesterol and the surface is attached to the carbohydrates.
- Nutrients and waste products are moved via passive transport (diffusion), easier transport, or active transport through the cell membrane.