Chemical Basis Of Life

• Chemical Basis of Life 1
• Macromolecules


  Very large, complex molecules built from multiple, repeating units added together
• Four classes of large biological molecules

  • Carbohydrates (sugars, starch, cellulose)
  • Lipids (fats/oils, phospholipids of biological membranes)
  • Nucleic acids (DNA and RNA)
  • Proteins (made from amino acids)
• Carbohydrates, nucleic acids and proteins are macromolecules
• Lipids aren't strictly macromolecules, but discussed here too
• Monomer


  Smaller units from which larger molecules are made
• Monomers


  • an amino acid (monomer for proteins)
  • a nucleotide (monomer for nucleic acids)
  • monomer for complex carbohydrates
• Carbohydrates


  Sugars, starch, cellulose
• Lipids


  Fats/oils, phospholipids of biological membranes
• Nucleic acids


  DNA and RNA
• Proteins


  Made from amino acids
• Lipids are not really macromolecules, but very important for life
• From little things, big things "grow"
• Cell membranes are made of lipids
• The Molecules of Life

  • Carbohydrates (sugars, starch, cellulose)
  • Lipids (fats/oils, phospholipids of biological membranes)
  • Nucleic acids (DNA and RNA)
  • Proteins (made from amino acids)
• Macromolecules


  • Built from multiple, repeating units added together
  • We need to know the units (monomer) for each, and how they join
• Concept 5.1 Macromolecules are polymers, built from monomers
• Concept 5.2: Carbohydrates serve as fuel and building material
• Concept 5.3 Lipids are a diverse group of hydrophobic molecules
• Concept 5.5: Nucleic acids store, transmit, and help express hereditary information
• Lipids


  • Not true polymers
  • Mix poorly with water (if at all) - insoluble in water
  • Mostly hydrogen and carbon
• Types of lipids


  • Fats and oils (triglycerides)
  • Phospholipids
  • Steroids
• Triglycerides


  Glycerol + three fatty acids
• Triglycerides (fats or oils)


  • Important energy source
• Phospholipids


  • Glycerol + phosphate group + two fatty acids
  • Lipid bilayers of membranes
• Phospholipids


  • Hydrophobic tails
  • Hydrophilic heads
• Steroids


  • Four fused rings with attached chemical groups
  • Component of cell membranes (cholesterol)
  • Signaling molecules that travel through the body (hormones)
• Lipids are essential for all living cells: energy storage, insulation, signalling, membrane structure
• Saturated fat


  Fatty acids have the maximum number of hydrogen atoms possible and no double bonds
• Unsaturated fat


  • Fatty acids have one or more double bonds
  • Cis double bond causes bending
• • Phospholipids self-assemble into double-layered sheets (bilayer)
  • This is the fundamental structure of cell membranes
• Steroids are lipids characterised by four carbon rings
• Cholesterol is a component in animal cell membranes and a precursor from which other steroids are synthesised
• Monomer


  Small, repeating "building blocks"
• Polymer


  Large molecules made from small, repeating monomers
• Dehydration reaction: synthesizing a polymer

  1. Unlinked monomer

  2. Dehydration removes a water molecule, forming a new bond

  3. Short polymer

  4. Longer polymer
• Hydrolysis: breaking down a polymer


  1. Longer polymer

  2. Hydrolysis adds a water molecule, breaking a bond

  3. Unlinked monomer
• Carbohydrates include sugars and polymers of sugars
• Carbohydrate monomers (monosaccharides)


  • Glucose
  • Fructose
  • Galactose
• Monosaccharides


  Simple sugars