Final answer:
Lipids are hydrophobic biological molecules that include triglycerides for energy storage, phospholipids for cell membrane structure, and steroids for membrane fluidity and hormone synthesis.
Step-by-step explanation:
Lipids: Structure and Function
Lipids are a diverse group of hydrophobic macromolecules that play crucial roles in living organisms. There are three major types of lipids: triglycerides (fats and oils), phospholipids, and steroids.
Triglycerides
Triglycerides, also known as triacylglycerols, consist of a glycerol molecule bonded to three fatty acid chains. They are the primary storage form of energy in the body and can contain either saturated or unsaturated fatty acids, which affect their properties and states at room temperature (solid or liquid).
Phospholipids
Phospholipids form the structural basis of cell membranes. Each molecule contains a glycerol backbone, two fatty acid tails, and a phosphate group, which has a polar head that is hydrophilic. This unique structure allows phospholipids to form bilayers in aqueous environments, creating the essential barrier for cells.
Steroids
Steroids are characterized by four fused carbon rings. Cholesterol is a well-known steroid that maintains the fluidity of cell membranes and serves as a precursor for steroid hormones such as testosterone, estrogen, and corticosteroids.
In the context of food, such as steak and cheese, one would expect a higher presence of saturated fatty acids due to their common occurrence in animal products, which are typically solid at room temperature.