Unit 1: Biochemistry - #3 Structure and Function of Macromolecules: Lipids (copy)

Lipids

• Lipids are nonpolar biological molecules  that provide long term energy storage, insulation, cushioning of internal organs and are the main component of the cell membrane 

• Lipids are the main structure of some hormones 

• All lipids are hydrophobic (do not dissolve in water) 

Five Main Types of Lipids

1. Fatty Acids

2. Fats

3. Phospholipids

4. Steroids

5. Waxes

Fatty Acid

• Consist of a long chain of carbon and hydrogen atoms with a terminal carboxyl functional group 

• Carboxyl gives its acidic properties 

• The longer the chain the more hydrophobic it becomes

What are the two types of Fatty Acids?

• Saturated

• Unsaturated

Saturated Fats

• Contain the maximum number of hydrogen atoms per carbon atom

• No double bonds - a straight chain

Unsaturated Fats

Contain a carbon double bond formed by removal of H from carbon skeleton - chain with a bend in it

Polyunsaturated

Contains more than one carbon double bond 

Fats

• Energy storage molecule - more than 2x energy than carbohydrates 

• The most common fat is the triglyceride which contain 3 fatty acid chains attached to a glycerol backbone. 

• They are linked with a dehydration synthesis reaction and are held together with an ester linkage.

Phospholipids

• The main component of cell membrane 

• Composed of two main parts, a phosphate head and two fatty acid tails 

• Amphipathic: The phosphate head is polar and hydrophilic while the fatty acid chains are nonpolar and hydrophobic (similar to soap) 

Steroids

• Consist of four linked carbon rings 

• Different steroids have different functional groups attached to the rings 

• Steroids rings are hydrophobic 

• Group of steroids Sterols, have a single polar -OH group at one end 

• Gives molecule dual solubility properties 

• Includes Cholesterol(component of the cell membrane), and sex hormones

Waxes

• Waxes are composed of long-chained fatty acids that are attached to an alcohol or a carbon ring

• Waxes are hydrophobic, non-polar and are firm yet pliable 

• EX. Cutin: Water resistant coating on plants, bird feathers, and beeswax