Lipids and Fatty Acids Quiz

Lipids

• Lipids are a family of biomolecules soluble in solvents but not in water
• The Greek word "lipos" means fat or lard
• Lipids are found in both plants and animals
• Lipids can be extracted from cells using organic solvents
• They are important components of cell membranes, fat-soluble vitamins, and steroid hormones

Sources of Lipids

• Found in meat, fish, oils, avocados, eggs, and legumes (nuts)

Properties of Lipids

• Insoluble in water but soluble in organic solvents
• Can be used as energy sources by animals
• Made up of fatty acids

Classes of Lipids

• Fatty Acids: a carboxylic acid with a long aliphatic chain
  • Saturated: all single bonds
  • Unsaturated: at least one double bond
    • Polyunsaturated: 2 or more double bonds
      • Most double bonds are cis-bonds causing a bend in the chain
• Waxes: fatty acid + long-chain alcohol
• Triglycerides: glycerol + 3 fatty acids (fats & oils)
• Phospholipids: glycerol + 2 fatty acids + phosphate + amino alcohol
• Glycolipids: glycerol or sphingosine + fatty acid + monosaccharide
• Steroids: 3 cyclohexanes + 1 cyclopentane fused together

Fatty Acids in the Human Body

• Essential fatty acids: polyunsaturated fatty acids that the body cannot make
  • Examples: linoleic acid and linolenic acid
  • Lack of essential fatty acids in infants can cause skin dermatitis

Cis and Trans Fatty Acids

• Cis fatty acids have hydrogens on the same side of the double bond, creating a kink
• Trans fatty acids have hydrogens on opposite sides of the double bond, resulting in a straighter chain

Triglycerides

• The structure of a triglyceride includes glycerol and three fatty acids
• Triglycerides make up fats and oils
• Fats are typically solid at room temperature and contain more saturated fatty acids
• Oils are typically liquid at room temperature and contain more unsaturated fatty acids

Hydrogenation of Oils

• Hydrogenation of oils converts unsaturated fatty acids into saturated ones.
• Partial hydrogenation can lead to the formation of trans-fatty acids

Trans Fats

• Trans fats are created when unsaturated fatty acids are partially hydrogenated
• They have longer shelf lives and are solid at room temperature
• Trans fats have both the benefits and drawbacks of saturated fats (longer shelf life, solid at room temperature) but can raise LDL cholesterol and lower HDL cholesterol

Steroids

• Steroids are a class of lipids with a specific structure
  • 3 fused 6-carbon atom rings and 1 5-carbon atom ring
• Important steroids include cholesterol, steroid hormones, and bile salts

Cholesterol

• A steroid found most often in humans and animals
• The body manufactures cholesterol, regardless of diet
• Cholesterol contains both hydrophobic and hydrophilic components (hydrocarbons are hydrophobic, and the OH group is hydrophilic)
• Overall, the molecule remains hydrophobic
• Cholesterol plays an important role in cell membranes, the production of bile acids, vitamin D, and steroid hormones.

Functions of Cholesterol

• Component of cell membranes, giving them structure and stability
• Forms a vital role in synthesizing other steroids e.g., bile salts
• Important for nerve transmission
• Important in producing vitamin D in the skin
• Excess cholesterol can lead to gallstones and plaque in arteries