Lecture Notes: Carbohydrates and Lipids - Focus on Lipids

Introduction to Lipids

• Lipids include a wide variety of molecules
• Common characteristic: hydrophobic (water-hating) due to being non-polar
• Not soluble in water
• Examples: fats, oils, waxes, steroids

Fatty Acid Structure

• Consist of carbon chains with hydrogens
• On either side: carboxyl group (CO) and methyl group (CH₃)
• Variations: length, saturation levels, bends

Formation of Triglycerides

• Made from glycerol and three fatty acid chains
• Glycerol: three-carbon molecule with three anchoring points
• Formed through condensation reactions (water removal)
• Entirely hydrophobic molecule

Phospholipids

• Amphipathic: have both hydrophobic and hydrophilic regions
• Structure: glycerol, two fatty acids, phosphate group
• Phosphate head: polar and hydrophilic (water-loving)
• Fatty acid tails: nonpolar and hydrophobic
• Spontaneously form bilayers, important in cell membranes

Types of Fatty Acids

Saturated Fatty Acids

• Straight chains with single bonds
• Typically solid at room temperature

Unsaturated Fatty Acids

• Bent chains due to double bonds
• Monounsaturated: one double bond
• Polyunsaturated: multiple double bonds
• Cis vs. Trans:
  • Cis: hydrogens on the same side, naturally occurring, bent
  • Trans: hydrogens on opposite sides, mostly man-made, straight

Triglycerides and Adipose Tissue

• Adipose tissue: fatty tissue under skin, around organs
• Function: long-term energy storage, thermal insulation, shock absorption
• Energy-dense: 9 calories per gram
• Example: blubber in arctic animals such as ringed seals

Phospholipids and Cell Membranes

• Contribute to cell membrane permeability
• Polar molecules (e.g., glucose) cannot pass through hydrophobic tails
• Nonpolar molecules (e.g., steroids like testosterone) can pass through

Steroids

• Not all steroids are harmful; some are essential
• Steroid hormones (e.g., testosterone) are lipid-based and hydrophobic
• Can pass through lipid bilayers, influencing hormone function

Key Takeaways

• Lipids are crucial for various functions like energy storage, insulation, and cellular structure.
• Understanding the form and function relationships is vital in grasping biological processes related to lipids.