Lipids and Lipids and Lipids – Oh My! Fat Fatty acid Steroids Palmitic acid Testosterone Triacylglycerol Estrogen Triglyceride Waxes Saturated fatty acid Lard Unsaturated fatty acid Omega-3-fatty acids Monounsaturated fatty acid Free fatty acids “Trans fatty acid” “Butter” Polyunsaturated fatty acid “Margarine” Stearic acid Olive oil Oleic acid Flax seed oil Oil “Toasted Sesame oil” Phospholipid Bile salts Cholesterol “Vegetable shortening” “Hydrogenated vegetable shortening” “Partially hydrogenated oil”

Lipids Lipids Lipids Relatively insoluble in water (hydrophobic) Consist mostly of carbon & hydrogen (hydrocarbons) very few oxygen molecules (thus hydrophobic) Greasy/oily consistency Some solid at room temp, others liquid at room temp Nutritionally significant forms: 1. Triglycerides (Fats & Oils) 2. Phospholipids 3. Sterols 4. Carotenoids

1) Triglycerides A.k.a. Are the most abundant lipids (95%) in living organisms Consist of a glycerol backbone + 3 fatty acids (FA) Efficient storage form of fuel Yields twice as many Calories (9 Calories/gm) as carbs Excess Carbs and excess proteins are converted into fat and stored as fat Functions: Cushion / pad Retain heat Make up 50% of cell mem. Make up certain hormones Store vitamins A, D, E, K Provide satiety

FAs may be saturated or unsaturated Solid at room temp Liquid at room temp Polyunsaturated FA

Lipids contain 2X Calories of Carbs and Proteins. 9 kilocalories/gm

extra Calories add up…

Most lipids are a mixture of saturated, monounsaturated, and polyunsaturated FAs

Making a good thing bad… Hydrogenation Lipids w unsaturated FAs typically cheaper shorter shelf life due to oxidation at points of unsaturation Tend to be too oily for some recipes E.g. cookies, muffins, breads… The Solution: add Hydrogen (by hydrogenation) and “saturate” the unsaturated FAs Longer shelf life. Slower to turn rancid. Thicker, more spreadable. Higher “smoking point.” Less likely to burn. Sometimes creates trans-fatty acids Classic e.g. = margarine

2) Phospholipids Consist of glycerol & 2 fatty acids and a phosphate group “heads” and “tails” 1o function is to serve as a cell membrane component Also plays role in emulsification of lipids for digestion E.g. Lecithin in bile E.g. transport of lipids in blood

3) Sterols) Consist of rings of carbon atoms Examples: Cholesterol stabilizer of cell membranes emulsifier in bile Some hormones Testosterone, Estrogen, Progesterone, & Cortisol

4) Carotenoids Plant pigments: usually Orange and yellow E.g. beta-carotene, lycopene, lutein, many others Often act as anti-oxidants May help prevent cell damage leading to cancers Some are the basis of Vit. A used to produce visual pigment retinal for both day and night vision