Lipids Fats, Oils, and Waxes

Introductory Video https://www.youtube.com/watch?v=VGHD9e3yRIU

Lipids A. Lipids 1. Lipids are varied in structure. 2. Many are insoluble in water because they lack polar groups

B. Fats and Oils Are Similar 1. Each fatty acid is a long hydrocarbon chain with a carboxyl (acid) group at one end. a. Because the carboxyl group is a polar group, fatty acids are soluble in water.

b. Most fatty acids in cells contain 16 to 18 carbon atoms per molecule.

Saturated vs. Unsaturated Fats c. Saturated fatty acids have no double bonds between their carbon atoms. (C-C-C-) d. Unsaturated fatty acids have double bonds in the carbon chain.(C-C-C-C=C-C-)  

Molecular shape of the Unsaturated bends due to the Double bond. This allows Unsaturated fatty acids to “flow” And are liquids at room temp. (oils)

e. Saturated animal fats are associated with circulatory disorders; plant oils can be substituted for animal fats in the diet.

What do the fatty acids attach to? 2. Glycerol is a water-soluble compound with three hydroxyl groups.

Another name for a Lipid….. 3. Triglycerides are glycerol joined to three fatty acids by condensation   (dehydration synthesis)

Triglyceride =

4. Fats are triglycerides containing saturated fatty acids (e. g 4. Fats are triglycerides containing saturated fatty acids (e.g., butter is solid at room temperature). 5. Oils are triglycerides with unsaturated fatty acids (e.g., corn oil is liquid at room temperature). 6. Fats function in long-term energy storage in organisms; store six times the energy as glycogen. They also provide insulation for organisms living in cold environments

C. Waxes Are Nonpolar Also 1. Waxes are a long-chain fatty acid bonded to a long-chain alcohol. a. Solid at room temperature; have a high melting point; are waterproof and resist degradation. b. Form protective covering that retards water loss in plants; maintain animal skin and fur.

D. Phospholipids Have a Polar Group (Make up Cell Membranes) 1. Phospholipids are like neutral fats except one fatty acid is replaced by phosphate group or a group with both phosphate and nitrogen  

Phosphate Gycerol Fatty Acid

(a) Structural formula (b) Space-filling model 2.Phosphate group is the polar head: hydrocarbon chain becomes nonpolar tails   CH2 O P CH C Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head Choline + Figure 5.13 N(CH3)3

3. Phospholipids arrange themselves in a double layer in water, so the polar heads face outward toward water molecules and nonpolar tails face toward each other away from water molecules. 4. This property enables them to form an interface or separation between two solutions (e.g., the interior and exterior of a cell); the plasma membrane is a phospholipid bilayer.

Hydrophilic head WATER Hydrophobic tail Figure 5.14

E. Steroids Have Carbon Rings 1. Steroids differ from neutral fats; steroids have a backbone of four fused carbon rings; vary according to attached functional groups. 2. Cholesterol is a precursor of other steroids, including aldosterone and sex hormones.  

3. Testosterone is the male sex hormone. 4. Functions vary due primarily to different attached functional groups.

Estradiol Testosterone CH3 OH HO O Estradiol Testosterone Female lion Male lion Figure 4.9