1. Chapter 5 The Structure and Function of Macromolecules
Lipids

2. Lipids Little to no affinity for water
Consist mostly of hydrocarbons although they may have some polar bonds due to the presence of oxygen
Major classes:
Fats
Phospholipids
Steroids

3. Fats Functions Energy storage Cushioning vital organs Insulation
Major function is energy storage / A gram of fat stores twice as much energy as a gram of protein or carbohydrates

4. Fats, cont’d Triglycerides or triacylglycerols
Consist of 1 glycerol + 3 fatty acids joined in a series of condensation reactions that lead to the formation of an ester bond between the glycerol molecule and each fatty acid
Glycerol is an alcohol with 3 carbons each bearing a hydroxyl group
Fatty acids have a carboxylic acid group with a long hydrocarbon tail

5. Figure 5.10 The synthesis and structure of a fat, or triacylglycerol

6. Fats, cont’d Saturated Fats Unsaturated Fats
The fatty acids in a fat can be the same or they can be of two or three different kinds
Fatty acids vary in length and in number and locations of double bonds
Saturated Fats
No double bonds in the fatty acid tails, hydrocarbon is “saturated” with hydrogen / tails pack closely / typically solids at room temperature / Ex: butter, lard
Unsaturated Fats
Fatty acids contain double bonds that generate kinks in the tails / tails cannot pack tightly / typically oils at room temperature / Ex: corn oil, cod liver oil

7. Figure 5.11 Examples of saturated and unsaturated fats and fatty acids

8. Phospholipids Major components of cell membranes
Composed of glycerol, two fatty acids, and a phosphate group
Additional small molecules, usually charged and polar, can be attached to the phosphate group (Ex: choline, serine, etc)
Have a hydrophilic head and a hydrophobic tail
Will self-assemble into aggregates when placed in an aqueous solution
Micelle
Phospholipid bilayer

9. Figure 5.12 The structure of a phospholipid

10. Figure 5.13 Two structures formed by self-assembly of phospholipids in aqueous environments   

11. Steroids A class of lipid hormones that consist of four fused rings
Steroid activity depends on the functional groups that are attached to the four fused rings (Ex: testosterone vs estradiol)
The steroid cholesterol is a common component of animal cell membranes and is a precursor from which other steroids are synthesized

12. Figure 5.14 Cholesterol, a steroid

13. Figure 4.8 A comparison of functional groups of female (estradiol) and male (testosterone) sex hormones