Lipids

• Lipids


  Large molecules that are not soluble in water, but are soluble in nonpolar solvents
• The most common lipid is fat. But steroids and fat soluble vitamins are also classed with lipids
• Functions of lipids


  • Important part of almost all cells
  • Found in cell membranes and brain and nervous tissue
  • Long-term energy storage in the body
  • Serve as insulation of body's organs against temperature change and shock
• Fats and oils generally provide 9 Cal/g of energy in our diet. These can be converted to glucose
• Classes of lipids


  • Triglycerides
  • Phosphoglycerides
  • Sphingolipids
  • Glycolipids
  • Steroids
  • Fat Soluble Vitamins
• The first four classes of lipids have at least one fatty acid
• Fatty acids


  Long hydrocarbon chains with a carboxyl group at one end
• Types of fatty acids

  • Saturated fatty acids
  • Monounsaturated fatty acids (cis)
  • Monounsaturated fatty acids (trans)
  • Polyunsaturated fatty acids (2 double bonds)
  • Polyunsaturated fatty acids (3 double bonds)
• Saturated fatty acids


  • Stack together very easily, so they are solid at room temperature
  • Raise the cholesterol in your blood
• Cis unsaturated fatty acids

  • Do not stack together well, so they tend to be liquids at room temperature
  • Vegetable oils contain cis fatty acids
  • The double bond tends to oxidize and the oil becomes rancid
• Trans fatty acids


  • Stack together well like saturated fatty acids
  • Raise the levels of low density lipoproteins (LDL) in the blood
  • LDL contain cholesterol which accumulates in the arteries leading to heart disease
  • Found in milk, fried foods, butter, cookies, crackers and vegetable shortening
• Hydrogenation


  Cis fatty acids + H2 (catalyst) -> Saturated fatty acid + Trans fatty acid
• Glycerol


  A 3-carbon alcohol
• Triglyceride with unsaturated fatty acids


  • Difficult for the molecules to stack together and form a solid

  
• Saponification


  Hydrolysis of a triglyceride with a strong base to produce glycerol and 3 salts of fatty acids

  
• Soap


  The salt of a fatty acid, with an ionic end and a long nonpolar tail
• Soap micelle


  • Nonpolar ends of molecules at the center are attracted to the circular nonpolar material, while the negatively charged groups on the surface are attracted to water molecules
• Lipid classes with two hydrophobic tails and a hydrophilic head

  • Glycolipids
  • Sphingolipids
  • Phosphoglycerides
• Functions of sphingolipids and phosphoglycerides

  • Forming the "lipid bilayer" of cell membranes
• Function of glycolipids


  • Found in brain and nervous tissue
• Lipid bilayer


  Two layers of lipid molecules with hydrophobic regions on the inside and hydrophilic regions on the outside, forming the cell membrane
• Another major function of sphingolipids is in forming the myelin sheath which protects or insulates nerve tissue

  
• Steroids


  • Cortisone
  • Cholesterol
  • Testosterone
  • Estrone
• Carbohydrates make up a large percentage of our diet and represent a major part of all organic matter on Earth
• Carbohydrates


  Contain carbon, hydrogen, and oxygen functional groups

  
• Photosynthesis


  CO2 + H2O + energy -> (CH2O)n
• Functions of carbohydrates in animals and humans

  • Energy source
  • Structural components
  • Provide 4 Cal/g of energy
• Functions of carbohydrates in plants

  • Energy storage
  • Structural components
  • Photosynthesis
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides

  
• Monosaccharides


  Simple sugars with the formula (CH2O)n, where n is usually 3, 4, 5, or 6

  
• Monosaccharides


  • Glucose
  • Fructose
  • Galactose

  
• Glycosidic linkage


  Bond formed between two monosaccharides
• Hemiacetal bond


  Bond formed between the carbonyl group of one monosaccharide and the hydroxyl group of another
• Ring structures of monosaccharides

  Glucose can form alpha and beta forms

  
• Galactose


  A monosaccharide sugar
• Starch foods like pasta, bread, and rice contain the alpha form of glucose, which we can digest. The beta form is found in wood and cellulose, which we cannot digest

  
• Ring Structures


  • C-C-C-C-O-C-CH2OH-H-OH-H-H-H-OH-H-OH-O-H
• α and β forms of glucose


  Differ only in the position of one hydroxyl group

  
• Glucose is a monosaccharide sugar

  
• The α form is found in starch foods like pasta, bread, and rice which we can digest. The β form is found in wood and cellulose which we cannot digest.