Chapter 13 Lipids Chemistry 20

Lipids - Family of bimolecules. - They are soluble in organic solvents but not in water (nonpolar). 1. Store energy: fat cells 2. Chemical messengers: find in nerve fibers and hormones. 3. Parts of membranes: not soluble in water

Lipids 1. Simple lipids: (Waxes, Fats & Oils) 2. Complex lipids (Glycerophospholipids) 3. Steroid (Cholesterol & steroid hormones) 4. Prostaglandins Store energy Cell membrane Chemical messenger Cell membrane Pain, fever, inflammation

Fatty acids Fatty acids are: Long-chain unbranched carbon attached to a carboxyl group. Typically carbon atoms. Insoluble in water. Saturated or unsaturated. Cis

Saturated and unsaturated Fatty acids Saturated fatty acids are solids at room temperature. Packed together  Maximum London dispersion forces Unsaturated fatty acids are liquids at room temperature. Can not pack together  London dispersion forces 

The human body is capable of synthesizing most fatty acids from carbohydrates or other fatty acids. Humans do not synthesize sufficient amounts of fatty acids that have more than one double bond. More than one double bond fatty acids are called essential fatty acids and they must be provided by the diet. Fatty acids

Long-chain alcohol Fatty acid Ester bond Waxes - are found in many plants and animals (or humans). - In plants, they help prevent loss of water and damage from pests. - In humans and animals, provide waterproof coating on skin and fur. Wax is an ester of saturated fatty acid and long chain alcohol.

Beeswax Carnauba Coating Jojoba Lanolin from wool lotions

Triacylglycerols are: Fats and oils (are stored in the body). Triesters of glycerol. Produced by Fischer esterification. Formed when the hydroxyl groups of glycerol react with the carboxyl groups of fatty acids. Triacylglycerols (Triglycerides)

glycerol three fatty acids triacylglycerol + 3H 2 O Esterification Acid

GLYCEROLGLYCEROL Fatty acid Triacylglycerols (Triglycerides) Produced by esterification of glycerol (a trihydroxyl alcohol). CH 2 CH CH 2 OH Glycerol

Triacylglycerols (Triglycerides) Fat: is a triacylglycerol that is solid at room temperature. Made by more saturated fatty acids. Meat, milk, butter and cheese (animal sources). Oil: is a triacylglycerol that is liquid at room temperature. Made by more unsaturated fatty acids. Corn, cotton seed, safflower and sunflower (plant sources). Both are colorless, odorless, and tasteless.

- Hydrogen adds to the double bonds of unsaturated fats (using transition metal catalyst such as Ni). - Melting point is increased. - Liquid oils are converted to semisolid fats. Hydrogenation _ C=C _ + H 2 → _ C _ C _ Ni HH HH HH

+ 3H 2 glyceryl Trioleate (triolein) glyceryl tristearate (tristearin) 1- Hydrogenation

2- Hydrolysis Triacylglycerols are hydrolysis (split by water) in the presence of strong acid or lipase (digestive enzyme). + 3H 2 O 3H3H + H + or Lipase H H H O

Is the process of forming “soaps” (salts of fatty acids). Is the reaction of a fat with a strong base (NaOH). Splits triacylglycerols into glycerol and the salts of fatty acids. With KOH or the oils that are polyunsaturated gives softer soaps (liquid soaps). Name of soap gives the source of the oil. 3- Saponification Like coconut or avocado soap

Saponification + 3NaOH 3+ “soap” Heat

GLYCEROLGLYCEROL Fatty acid phosphate Amino alcohol Glycerophospholipids Polar part (polar head) and nonpolar part (nonpolar tail) P O O O O_O_ N CH 3 HO – CH 2 _ CH 2 CH 3 + Interact with both polar and nonpolar substances. 1. Most abundant lipids in cell membranes (semipermeable). 2. Combine with less polar triglycerides and cholesterol to make them soluble. Choline

Steroids have: A steroid nucleus which is 4 carbon rings. Attached groups that make the different types of compounds. No fatty acids. steroid nucleus Steroids

Cholesterol: Is the most abundant steroid in the body. Insoluble in water (need a water soluble carrier). Has methyl CH 3 - groups, alkyl chain, and -OH attached to the steroid nucleus. Cholesterol

Cholesterol: Is obtained from meats, milk, and eggs. Is synthesized in the liver from fats, carbohydrates and proteins. Is needed for cell membranes, brain and nerve tissue, steroid hormones, and Vitamin D. Clogs arteries when high levels form plaque. No cholesterol in vegetable and plants. At artery clogged by cholesterol plaque Cholesterol Gallstones form in gallbladder

Steroid hormones are: Chemical messengers in body Sex hormones Testosterone & androsterone in males Estrogen & progesterone in females Testosterone (androgen) Male sex hormone Estrogen Female sex hormone Steroids

Triacylglycerols Lipoproteins Transporting lipids through the bloodstream to tissues where they are stored, Used for energy, or to make hormones. Spherical particles Polar surface and nonpolar inner Water-soluble form of lipids (soluble in blood)

Lipoproteins VLDL: very- low-density lipoprotein LDL: low-density lipoprotein HDL: high-density lipoprotein Chylomicrons Liver Fat storage cells Heart and muscles LDL VLDL HDL Energy Intestine and elimination Triglycerides and Cholesterol Cholesterol Triglycerides and Cholesterol

Cell Membrane Semipermeable: nutrients can enter and waste products can leave. Fluid mosaic model Nonpolar Polar Phospholipid bilayer Carbohydrate