Chapter 21: Biochemistry
21.3: Lipids
- Lipids
- Nonpolar organic molecules composed primarily of carbon, hydrogen, and oxygen. They are insoluble in water but soluble in nonpolar solvents.
- Fatty Acids
- Long hydrocarbon chains with a carboxylic acid group (-COOH) at one end. They can be saturated or unsaturated.
- Triglycerides
- Composed of one glycerol molecule bonded to three fatty acids. They serve as a major energy storage molecule.
- Phospholipids
- Lipids containing a phosphate group, which makes them amphipathic. They form the bilayer structure of cell membranes.
- Steroids
- Lipids with a characteristic four-ring structure (e.g., cholesterol, hormones).
Functions of Lipids
- Energy Storage: Triglycerides store energy efficiently for long-term use.
- Structural Role: Phospholipids form the structural framework of cell membranes.
- Insulation and Protection: Fat provides thermal insulation and protects organs.
- Regulation: Steroids regulate various biological processes, including metabolism and reproduction.
Types of Lipids
- Fatty Acids: Saturated and unsaturated fatty acids serve as building blocks for other lipids.
- Triglycerides: Found in animal fats and plant oils, they are a primary energy source.
- Phospholipids: Essential for forming cell membranes.
- Steroids: Cholesterol and hormones like testosterone and estrogen.
Importance of Lipids
- Provide twice as much energy per gram as carbohydrates or proteins.
- Essential for maintaining cell membrane integrity.
- Act as precursors for hormones and vitamins.
- Help in absorption of fat-soluble vitamins (A, D, E, K).
Questions for Students
- What are lipids, and why are they insoluble in water?
- Define fatty acids, and differentiate between saturated and unsaturated fatty acids.
- Explain the role of phospholipids in cell membranes.
- What is the structural difference between triglycerides and steroids?
- How do lipids serve as energy storage molecules in the body?