1.5.A—Describe the structure and function of lipids

Describe the structure and function of lipids.

• Lipids are typically nonpolar, hydrophobic molecules whose structure and function are derived from the way their subcomponents are assembled. Fatty acids can be described as either saturated or unsaturated.
  • i. Saturated fatty acids contain only single bonds between carbon atoms.
  • ii. Unsaturated fatty acids contain at least one double bond between carbon atoms, which causes the carbon chain to kink.
  • iii. The more double bonds in a fatty acid tail, the more unsaturated the lipid becomes.
  • iv. The more unsaturated a lipid is, the more liquid it is at room temperature.
• Lipids provide a variety of functions for living organisms. Some examples of lipids are fats, steroids including cholesterol, and phospholipids.
  • i. Fats provide energy storage and support cell function. In some cases, they can also provide insulation to help keep mammals warm.
  • ii. Steroids are hormones that support physiological functions including growth and development, energy metabolism, and homeostasis.
  • iii. Cholesterol provides essential structural stability to animal cell membranes.
  • iv. Phospholipids group together to form the lipid bilayers found in plasma and cell membranes.
  • Exclusion: The molecular structure of specific lipids is beyond the scope of the AP Exam.