Lesson 3 Lipids

Lipids Hydrophobic, non-polar Energy storage, building membranes, chemical signalling 4 main types: Fats Phospholipids Steroids waxes

1. Fats Energy storage Insulation Cushioning Carry more energy than carbohydrates Harder to break down Insulation Cushioning

Fats 1 +3 = Triglycerides: most common fats in plants and animals Glycerol backbone + 3 fatty acids Glycerol is an alcohol Fatty acids are long hydrocarbon chains (16C – 18C) Formed with dehydration synthesis 1 +3 =

Types of fatty acids Saturated Unsaturated No double bonds Solid at room temperature Animal fats, butter, lard Unsaturated Have double bonds Liquid at room temperature Plant fats

Two different unsaturated fats Cis fat Hydrogens on same side of double bond Trans fat Hydrogens on different sides of double bond Why is one good and one bad?

Fats and health Straight fats are bad Bent fats are good Saturated Trans unsaturated Even worse b/c db is hard to break down Found in fried foods, processed foods, hard margarines Bent fats are good Cis unsaturated Found in vegetables, nuts

2. Phospholipids Make up most of cell membrane Glycerol + polar phosphate group + 2 fatty acids Phosphate “head” is hydrophilic Fatty acid tail is hydrophobic

Phospholipids Phospholipid bilayer in cell membrane Polar and charged molecules cannot pass through

3. Sterols (steroids) Highly hydrophobic Four rings with varying functional groups attached Responsible for carrying messages and maintaining fluidity Ex. Cholesterol Sex hormones such as testosterone and estrogen

4. Waxes Hydrophobic solids Used by animals and plants as waterproofing agents Ex. Cutin in plants, beeswax, feathers of birds

Homework Describe the general characteristics of lipids and how they are different from carbohydrates. Compare the chemical energy stored in a gram of fat to the chemical energy stored in a gram of carbohydrate or protein. What are the functions of fats in living organisms? What is the most common type of fat found in the body? Describe its chemical structure. Draw the condensation reaction that takes place to form a triglyceride. Draw a diagram of a saturated fatty acid and an unsaturated fatty acid What are the difference in properties between a triglyceride containing only saturated fatty acids and a triglyceride containing unsaturated fatty acids? Describe the structure and function of a phospholipid. Draw a simple diagram of a phospholipid How do phospholipids play a role in the cell membrane? Describe the structure of steroids and draw cholesterol. What is the function of cholesterol? What are the dangers of a high concentration of cholesterol in the blood stream? Describe the general function of waxes.